Internet Engineering Task Force (IETF)                      G. Fairhurst
Request for Comments: 9065                        University of Aberdeen
Category: Informational                                       C. Perkins
ISSN: 2070-1721                                    University of Glasgow
                                                               July 2021

Considerations around Transport Header Confidentiality, Network Operations, and the Evolution of Internet Transport Protocols




To protect user data and privacy, Internet transport protocols have supported payload encryption and authentication for some time. Such encryption and authentication are now also starting to be applied to the transport protocol headers. This helps avoid transport protocol ossification by middleboxes, mitigate attacks against the transport protocol, and protect metadata about the communication. Current operational practice in some networks inspect transport header information within the network, but this is no longer possible when those transport headers are encrypted.


This document discusses the possible impact when network traffic uses a protocol with an encrypted transport header. It suggests issues to consider when designing new transport protocols or features.


Status of This Memo


This document is not an Internet Standards Track specification; it is published for informational purposes.


This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are candidates for any level of Internet Standard; see Section 2 of RFC 7841.

この文書は、インターネットエンジニアリングタスクフォース(IETF)の製品です。IETFコミュニティのコンセンサスを表します。それは公開レビューを受け、インターネットエンジニアリングステアリンググループ(IESG)による出版の承認を受けました。IESGによって承認されたすべての文書がすべてのレベルのインターネット規格の候補者ではありません。RFC 7841のセクション2を参照してください。

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at


Copyright Notice


Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved.

著作権(C)2021 IETF信頼と文書著者として識別された人。全著作権所有。

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

このドキュメントは、このドキュメントの発行日に有効なBCP 78およびIETFドキュメントに関連するIETFトラストの法的規定(の対象となります。 これらのドキュメントは、このドキュメントに関するお客様の権利と制限について説明しているため、注意深く確認してください。 このドキュメントから抽出されたコードコンポーネントには、Trust LegalProvisionsのセクション4.eで説明されているSimplifiedBSD Licenseテキストが含まれている必要があり、Simplified BSDLicenseで説明されているように保証なしで提供されます。

Table of Contents


   1.  Introduction
   2.  Current Uses of Transport Headers within the Network
     2.1.  To Separate Flows in Network Devices
     2.2.  To Identify Transport Protocols and Flows
     2.3.  To Understand Transport Protocol Performance
     2.4.  To Support Network Operations
     2.5.  To Mitigate the Effects of Constrained Networks
     2.6.  To Verify SLA Compliance
   3.  Research, Development, and Deployment
     3.1.  Independent Measurement
     3.2.  Measurable Transport Protocols
     3.3.  Other Sources of Information
   4.  Encryption and Authentication of Transport Headers
   5.  Intentionally Exposing Transport Information to the Network
     5.1.  Exposing Transport Information in Extension Headers
     5.2.  Common Exposed Transport Information
     5.3.  Considerations for Exposing Transport Information
   6.  Addition of Transport OAM Information to Network-Layer Headers
     6.1.  Use of OAM within a Maintenance Domain
     6.2.  Use of OAM across Multiple Maintenance Domains
   7.  Conclusions
   8.  Security Considerations
   9.  IANA Considerations
   10. Informative References
   Authors' Addresses
1. Introduction
1. はじめに

The transport layer supports the end-to-end flow of data across a network path, providing features such as connection establishment, reliability, framing, ordering, congestion control, flow control, etc., as needed to support applications. One of the core functions of an Internet transport is to discover and adapt to the characteristics of the network path that is currently being used.


For some years, it has been common for the transport-layer payload to be protected by encryption and authentication but for the transport-layer headers to be sent unprotected. Examples of protocols that behave in this manner include Transport Layer Security (TLS) over TCP [RFC8446], Datagram TLS [RFC6347] [DTLS], the Secure Real-time Transport Protocol [RFC3711], and tcpcrypt [RFC8548]. The use of unencrypted transport headers has led some network operators, researchers, and others to develop tools and processes that rely on observations of transport headers both in aggregate and at the flow level to infer details of the network's behaviour and inform operational practice.

何年もの間、トランスポート層のペイロードは暗号化と認証によって保護されるのが一般的でしたが、トランスポート層のヘッダーが保護されていない送信されます。このように動作するプロトコルの例には、TCP [RFC8446]、データグラムTLS [RFC6347] [DTLS]、セキュアリアルタイムトランスポートプロトコル[RFC3711]、およびTCPCRYPT [RFC8548]を介したトランスポート層セキュリティ(TLS)が含まれます。暗号化されていないトランスポートヘッダーの使用は、ネットワークの行動の詳細を推測し、運用慣行の詳細を推測するために、集約およびフローレベルの両方でのトランスポートヘッダーの観測に依存するツールとプロセスを開発するために、ネットワーク事業者、研究者などがいくつかのネットワーク事業者、およびプロセスを開発しました。

Transport protocols are now being developed that encrypt some or all of the transport headers, in addition to the transport payload data. The QUIC transport protocol [RFC9000] is an example of such a protocol. Such transport header encryption makes it difficult to observe transport protocol behaviour from the vantage point of the network. This document discusses some implications of transport header encryption for network operators and researchers that have previously observed transport headers, and it highlights some issues to consider for transport protocol designers.


As discussed in [RFC7258], the IETF has concluded that Pervasive Monitoring (PM) is a technical attack that needs to be mitigated in the design of IETF protocols. This document supports that conclusion. It also recognises that [RFC7258] states, "Making networks unmanageable to mitigate PM is not an acceptable outcome, but ignoring PM would go against the consensus documented here. An appropriate balance will emerge over time as real instances of this tension are considered." This document is written to provide input to the discussion around what is an appropriate balance by highlighting some implications of transport header encryption.

[RFC7258]で説明したように、IETFは、Pervasive Monitoring(PM)がIETFプロトコルの設計において軽減される必要がある技術攻撃であると結論しました。この文書はその結論をサポートしています。また、[RFC7258]は、「PMを軽減するために管理不能なネットワークを作る」と認識していますが、PMはここに記載されているコンセンサスに対して行くでしょう。この緊張の実際のインスタンスが考慮されるにつれて、適切なバランスは時間が経つにつれて発生します。」この文書は、トランスポートヘッダ暗号化の影響を強調することによって適切なバランスがあるのかについての議論への入力を提供するように書かれています。

Current uses of transport header information by network devices on the Internet path are explained. These uses can be beneficial or malicious. This is written to provide input to the discussion around what is an appropriate balance by highlighting some implications of transport header encryption.


2. Current Uses of Transport Headers within the Network
2. ネットワーク内のトランスポートヘッダの現在の使用

In response to pervasive surveillance [RFC7624] revelations and the IETF consensus that "Pervasive Monitoring Is an Attack" [RFC7258], efforts are underway to increase encryption of Internet traffic. Applying confidentiality to transport header fields can improve privacy and can help to mitigate certain attacks or manipulation of packets by devices on the network path, but it can also affect network operations and measurement [RFC8404].

Pervasive Surveillance [RFC7624]の啓示とIETFコンセンサスとの間で、「Pervasive Monitoringは攻撃である」[RFC7258]、インターネットトラフィックの暗号化を高めるための努力が進行中です。輸送ヘッダーフィールドへの機密性を適用することで、プライバシーを向上させることができ、ネットワーク経路上のデバイスによるパケットの特定の攻撃や操作を軽減するのに役立ちますが、ネットワーク操作と測定[RFC8404]にも影響を与える可能性があります。

When considering what parts of the transport headers should be encrypted to provide confidentiality and what parts should be visible to network devices (including unencrypted but authenticated headers), it is necessary to consider both the impact on network operations and management and the implications for ossification and user privacy [Measurement]. Different parties will view the relative importance of these concerns differently. For some, the benefits of encrypting all the transport headers outweigh the impact of doing so; others might analyse the security, privacy, and ossification impacts and arrive at a different trade-off.


This section reviews examples of the observation of transport-layer headers within the network by using devices on the network path or by using information exported by an on-path device. Unencrypted transport headers provide information that can support network operations and management, and this section notes some ways in which this has been done. Unencrypted transport header information also contributes metadata that can be exploited for purposes unrelated to network transport measurement, diagnostics, or troubleshooting (e.g., to block or to throttle traffic from a specific content provider), and this section also notes some threats relating to unencrypted transport headers.


Exposed transport information also provides a source of information that contributes to linked data sets, which could be exploited to deduce private information, e.g., user patterns, user location, tracking behaviour, etc. This might reveal information the parties did not intend to be revealed. [RFC6973] aims to make designers, implementers, and users of Internet protocols aware of privacy-related design choices in IETF protocols.

露光されたトランスポート情報はまた、リンクされたデータセットに貢献する情報の源を提供します。これは、ユーザーパターン、ユーザーの場所、追跡行動などの個人情報を推測するために悪用される可能性があります。。[RFC6973] IETFプロトコルでのプライバシー関連の設計選択を意識したインターネットプロトコルの設計者、実装者、およびユーザを作ることを目的としています。

This section does not consider intentional modification of transport headers by middleboxes, such as devices performing Network Address Translation (NAT) or firewalls.


2.1. To Separate Flows in Network Devices
2.1. ネットワークデバイスのフローを分離するために

Some network-layer mechanisms separate network traffic by flow without resorting to identifying the type of traffic: hash-based load sharing across paths (e.g., Equal-Cost Multipath (ECMP)); sharing across a group of links (e.g., using a Link Aggregation Group (LAG)); ensuring equal access to link capacity (e.g., Fair Queuing (FQ)); or distributing traffic to servers (e.g., load balancing). To prevent packet reordering, forwarding engines can consistently forward the same transport flows along the same forwarding path, often achieved by calculating a hash using an n-tuple gleaned from a combination of link header information through to transport header information. This n-tuple can use the Media Access Control (MAC) address and IP addresses and can include observable transport header information.

いくつかのネットワーク層メカニズムは、トラフィックの種類を識別することなく、フローによってネットワークトラフィックを分離します。パス間のハッシュベースの負荷分散(例えば、等価マルチパス(ECMP));リンクのグループを横切って(例えば、リンクアグリゲーショングループ(LAG)を使用する)。リンク容量への等しいアクセスを確保する(例えば、公平なキューイング(FQ))。またはトラフィックをサーバーに配布する(たとえば、ロードバランシング)。パケットの並べ替えを防ぐために、転送エンジンは、同じ転送の流れを常に前方に転送することができ、リンクヘッダ情報の組み合わせから転送ヘッダ情報を介してGreatedからGreated N - Tupleを使用してハッシュを計算することによって達成される。このn-タプルは、メディアアクセス制御(MAC)アドレスとIPアドレスを使用でき、観察可能なトランスポートヘッダ情報を含めることができます。

When transport header information cannot be observed, there can be less information to separate flows at equipment along the path. Flow separation might not be possible when a transport forms traffic into an encrypted aggregate. For IPv6, the Flow Label [RFC6437] can be used even when all transport information is encrypted, enabling Flow Label-based ECMP [RFC6438] and load sharing [RFC7098].

トランスポートヘッダ情報を観察できない場合、経路に沿って機器でフローを分離するための情報が少ない可能性があります。トランスポートが暗号化された集計にトラフィックを形成するとき、フロー分離は不可能かもしれません。IPv6の場合、すべてのトランスポート情報が暗号化されていてもフローラベル[RFC6437]を使用でき、フローラベルベースのECMP [RFC6438]とロード・シェアリング[RFC7098]を有効にできます。

2.2. To Identify Transport Protocols and Flows
2.2. トランスポートプロトコルとフローを特定するため

Information in exposed transport-layer headers can be used by the network to identify transport protocols and flows [RFC8558]. The ability to identify transport protocols, flows, and sessions is a common function performed, for example, by measurement activities, Quality of Service (QoS) classifiers, and firewalls. These functions can be beneficial and performed with the consent of, and in support of, the end user. Alternatively, the same mechanisms could be used to support practises that might be adversarial to the end user, including blocking, deprioritising, and monitoring traffic without consent.


Observable transport header information, together with information in the network header, has been used to identify flows and their connection state, together with the set of protocol options being used. Transport protocols, such as TCP [RFC7414] and the Stream Control Transmission Protocol (SCTP) [RFC4960], specify a standard base header that includes sequence number information and other data. They also have the possibility to negotiate additional headers at connection setup, identified by an option number in the transport header.

観測可能なトランスポートヘッダ情報は、ネットワークヘッダ内の情報と共に、使用されているプロトコルオプションのセットと共にフローおよびそれらの接続状態を識別するために使用されてきた。TCP [RFC7414]やStream Control Transmission Protocol(SCTP)[RFC4960]などのトランスポートプロトコルは、シーケンス番号情報やその他のデータを含む標準ベースヘッダーを指定します。それらはまた、トランスポートヘッダ内のオプション番号によって識別される接続セットアップで追加のヘッダーをネゴシエートする可能性もあります。

In some uses, an assigned transport port (e.g., 0..49151) can identify the upper-layer protocol or service [RFC7605]. However, port information alone is not sufficient to guarantee identification. Applications can use arbitrary ports and do not need to use assigned port numbers. The use of an assigned port number is also not limited to the protocol for which the port is intended. Multiple sessions can also be multiplexed on a single port, and ports can be reused by subsequent sessions.


Some flows can be identified by observing signalling data (e.g., see [RFC3261] and [RFC8837]) or through the use of magic numbers placed in the first byte(s) of a datagram payload [RFC7983].


When transport header information cannot be observed, this removes information that could have been used to classify flows by passive observers along the path. More ambitious ways could be used to collect, estimate, or infer flow information, including heuristics based on the analysis of traffic patterns, such as classification of flows relying on timing, volumes of information, and correlation between multiple flows. For example, an operator that cannot access the Session Description Protocol (SDP) session descriptions [RFC8866] to classify a flow as audio traffic might instead use (possibly less-reliable) heuristics to infer that short UDP packets with regular spacing carry audio traffic. Operational practises aimed at inferring transport parameters are out of scope for this document, and are only mentioned here to recognise that encryption does not prevent operators from attempting to apply practises that were used with unencrypted transport headers.


The IAB [RFC8546] has provided a summary of expected implications of increased encryption on network functions that use the observable headers and describe the expected benefits of designs that explicitly declare protocol-invariant header information that can be used for this purpose.

IAB [RFC8546]は、観察可能なヘッダーを使用するネットワーク機能に対する暗号化の予想される影響の要約を提供し、この目的のために使用できるプロトコル不変ヘッダー情報を明示的に宣言する設計の予想される利点を説明しました。

2.3. To Understand Transport Protocol Performance
2.3. トランスポートプロトコルのパフォーマンスを理解する

This subsection describes use by the network of exposed transport-layer headers to understand transport protocol performance and behaviour.


2.3.1. Using Information Derived from Transport-Layer Headers
2.3.1. トランスポートレイヤヘッダーから派生した情報を使用する

Observable transport headers enable explicit measurement and analysis of protocol performance and detection of network anomalies at any point along the Internet path. Some operators use passive monitoring to manage their portion of the Internet by characterising the performance of link/network segments. Inferences from transport headers are used to derive performance metrics:


Traffic Rate and Volume: Per-application traffic rate and volume measures can be used to characterise the traffic that uses a network segment or the pattern of network usage. Observing the protocol sequence number and packet size offers one way to measure this (e.g., measurements observing counters in periodic reports, such as RTCP [RFC3550] [RFC3711] [RFC4585], or measurements observing protocol sequence numbers in statistical samples of packet flows or specific control packets, such as those observed at the start and end of a flow).

トラフィックレートとボリューム:アプリケーションごとのトラフィックレートとボリューム測定は、ネットワークセグメントまたはネットワーク使用のパターンを使用するトラフィックを特徴付けるために使用できます。プロトコルシーケンス番号とパケットサイズを観察すると、これを測定する1つの方法があります(例えば、RTCP [RFC3550] [RFC3711] [RFC4585]などの周期的レポート、またはパケットフローの統計的サンプル内のプロトコルシーケンス番号の測定値などの測定値)。流れの開始と終わりに見られるものなどの特定の制御パケット。

Measurements can be per endpoint or for an endpoint aggregate. These could be used to assess usage or for subscriber billing.


Such measurements can be used to trigger traffic shaping and to associate QoS support within the network and lower layers. This can be done with consent and in support of an end user to improve quality of service or could be used by the network to deprioritise certain flows without user consent.


The traffic rate and volume can be determined, providing that the packets belonging to individual flows can be identified, but there might be no additional information about a flow when the transport headers cannot be observed.


Loss Rate and Loss Pattern: Flow loss rate can be derived (e.g., from transport sequence numbers or inferred from observing transport protocol interactions) and has been used as a metric for performance assessment and to characterise transport behaviour. Network operators have used the variation in patterns to detect changes in the offered service. Understanding the location and root cause of loss can help an operator determine whether this requires corrective action.


There are various causes of loss, including: corruption of link frames (e.g., due to interference on a radio link); buffering loss (e.g., overflow due to congestion, Active Queue Management (AQM) [RFC7567], or inadequate provision following traffic preemption), and policing (e.g., traffic management [RFC2475]). Understanding flow loss rates requires maintaining the per-flow state (flow identification often requires transport-layer information) and either observing the increase in sequence numbers in the network or transport headers or comparing a per-flow packet counter with the number of packets that the flow actually sent. Per-hop loss can also sometimes be monitored at the interface level by devices on the network path or by using in-situ methods operating over a network segment (see Section 3.3).


The pattern of loss can provide insight into the cause of loss. Losses can often occur as bursts, randomly timed events, etc. It can also be valuable to understand the conditions under which loss occurs. This usually requires relating loss to the traffic flowing at a network node or segment at the time of loss. Transport header information can help identify cases where loss could have been wrongly identified or where the transport did not require retransmission of a lost packet.


Throughput and Goodput: Throughput is the amount of payload data sent by a flow per time interval. Goodput (the subset of throughput consisting of useful traffic; see Section 2.5 of [RFC7928] and [RFC5166]) is a measure of useful data exchanged. The throughput of a flow can be determined in the absence of transport header information, providing that the individual flow can be identified, and the overhead known. Goodput requires the ability to differentiate loss and retransmission of packets, for example, by observing packet sequence numbers in the TCP or RTP headers [RFC3550].


Latency: Latency is a key performance metric that impacts application and user-perceived response times. It often indirectly impacts throughput and flow completion time. This determines the reaction time of the transport protocol itself, impacting flow setup, congestion control, loss recovery, and other transport mechanisms. The observed latency can have many components [Latency]. Of these, unnecessary/unwanted queueing in buffers of the network devices on the path has often been observed as a significant factor [bufferbloat]. Once the cause of unwanted latency has been identified, this can often be eliminated.


To measure latency across a part of a path, an observation point [RFC7799] can measure the experienced round-trip time (RTT) by using packet sequence numbers and acknowledgements or by observing header timestamp information. Such information allows an observation point on the network path to determine not only the path RTT but also allows measurement of the upstream and downstream contribution to the RTT. This could be used to locate a source of latency, e.g., by observing cases where the median RTT is much greater than the minimum RTT for a part of a path.


      The service offered by network operators can benefit from latency
      information to understand the impact of configuration changes and
      to tune deployed services.  Latency metrics are key to evaluating
      and deploying AQM [RFC7567], Diffserv [RFC2474], and Explicit
      Congestion Notification (ECN) [RFC3168] [RFC8087].  Measurements
      could identify excessively large buffers, indicating where to
      deploy or configure AQM.  An AQM method is often deployed in
      combination with other techniques, such as scheduling [RFC7567]
      [RFC8290], and although parameter-less methods are desired
      [RFC7567], current methods often require tuning [RFC8290]
      [RFC8289] [RFC8033] because they cannot scale across all possible
      deployment scenarios.

Latency and round-trip time information can potentially expose some information useful for approximate geolocation, as discussed in [PAM-RTT].


Variation in Delay: Some network applications are sensitive to (small) changes in packet timing (jitter). Short- and long-term delay variation can impact the latency of a flow and hence the perceived quality of applications using a network path. For example, jitter metrics are often cited when characterising paths supporting real-time traffic. The expected performance of such applications can be inferred from a measure of the variation in delay observed along a portion of the path [RFC3393] [RFC5481]. The requirements resemble those for the measurement of latency.

遅延の変動:一部のネットワークアプリケーションは、パケットタイミング(ジッタ)の(小)変更に敏感です。短期間の遅延の変動は、流速の待ち時間、したがってネットワーク経路を使用しているアプリケーションの質に影響を与える可能性があります。たとえば、リアルタイムトラフィックをサポートするパスを特徴付ける場合、ジッタメトリックはしばしば引用されます。そのような用途の予想される性能は、経路の一部に沿って観察された遅延の変動の尺度から推測することができる[RFC3393] [RFC5481]。要件は待ち時間の測定のためにそれらに似ています。

Flow Reordering: Significant packet reordering within a flow can impact time-critical applications and can be interpreted as loss by reliable transports. Many transport protocol techniques are impacted by reordering (e.g., triggering TCP retransmission or rebuffering of real-time applications). Packet reordering can occur for many reasons, e.g., from equipment design to misconfiguration of forwarding rules. Flow identification is often required to avoid significant packet misordering (e.g., when using ECMP, or LAG). Network tools can detect and measure unwanted/excessive reordering and the impact on transport performance.


There have been initiatives in the IETF transport area to reduce the impact of reordering within a transport flow, possibly leading to a reduction in the requirements for preserving ordering. These have potential to simplify network equipment design as well as the potential to improve robustness of the transport service. Measurements of reordering can help understand the present level of reordering and inform decisions about how to progress new mechanisms.


Techniques for measuring reordering typically observe packet sequence numbers. Metrics have been defined that evaluate whether a network path has maintained packet order on a packet-by-packet basis [RFC4737] [RFC5236]. Some protocols provide in-built monitoring and reporting functions. Transport fields in the RTP header [RFC3550] [RFC4585] can be observed to derive traffic volume measurements and provide information on the progress and quality of a session using RTP. Metadata assists in understanding the context under which the data was collected, including the time, observation point [RFC7799], and way in which metrics were accumulated. The RTCP protocol directly reports some of this information in a form that can be directly visible by devices on the network path.

並べ替えを測定するための技術は、通常、パケットシーケンス番号を観察します。ネットワークパスがパケットごとにパケット順を維持したかどうかを評価するメトリックが定義されています[RFC4737] [RFC5236]。一部のプロトコルは、内蔵の監視機能とレポート作成機能を提供します。RTPヘッダ[RFC3550] [RFC4585]のトランスポートフィールドは、トラフィック量の測定値を導出し、RTPを使用してセッションの進行と品質に関する情報を提供することができます。メタデータは、時間、観測点[RFC7799]、およびメトリックが蓄積された方法を含む、データが収集されたコンテキストを理解するのに役立ちます。RTCPプロトコルは、ネットワークパス上のデバイスで直接表示できる形式でこの情報の一部を直接報告します。

In some cases, measurements could involve active injection of test traffic to perform a measurement (see Section 3.4 of [RFC7799]). However, most operators do not have access to user equipment; therefore, the point of test is normally different from the transport endpoint. Injection of test traffic can incur an additional cost in running such tests (e.g., the implications of capacity tests in a mobile network segment are obvious). Some active measurements [RFC7799] (e.g., response under load or particular workloads) perturb other traffic and could require dedicated access to the network segment.


Passive measurements (see Section 3.6 of [RFC7799]) can have advantages in terms of eliminating unproductive test traffic, reducing the influence of test traffic on the overall traffic mix, and having the ability to choose the point of observation (see Section 2.4.1). Measurements can rely on observing packet headers, which is not possible if those headers are encrypted, but could utilise information about traffic volumes or patterns of interaction to deduce metrics.


Passive packet sampling techniques are also often used to scale the processing involved in observing packets on high-rate links. This exports only the packet header information of (randomly) selected packets. Interpretation of the exported information relies on understanding of the header information. The utility of these measurements depends on the type of network segment/link and number of mechanisms used by the network devices. Simple routers are relatively easy to manage, but a device with more complexity demands understanding of the choice of many system parameters.


2.3.2. Using Information Derived from Network-Layer Header Fields
2.3.2. ネットワーク層ヘッダフィールドから派生した情報を使用する

Information from the transport header can be used by a multi-field (MF) classifier as a part of policy framework. Policies are commonly used for management of the QoS or Quality of Experience (QoE) in resource-constrained networks or by firewalls to implement access rules (see also Section 2.2.2 of [RFC8404]). Policies can support user applications/services or protect against unwanted or lower-priority traffic (Section 2.4.4).


Transport-layer information can also be explicitly carried in network-layer header fields that are not encrypted, serving as a replacement/addition to the exposed transport header information [RFC8558]. This information can enable a different forwarding treatment by the devices forming the network path, even when a transport employs encryption to protect other header information.


On the one hand, the user of a transport that multiplexes multiple subflows might want to obscure the presence and characteristics of these subflows. On the other hand, an encrypted transport could set the network-layer information to indicate the presence of subflows and to reflect the service requirements of individual subflows. There are several ways this could be done:


IP Address: Applications normally expose the endpoint addresses used in the forwarding decisions in network devices. Address and other protocol information can be used by an MF classifier to determine how traffic is treated [RFC2475] and hence affects the quality of experience for a flow. Common issues concerning IP address sharing are described in [RFC6269].


Using the IPv6 Network-Layer Flow Label: A number of Standards Track and Best Current Practice RFCs (e.g., [RFC8085], [RFC6437], and [RFC6438]) encourage endpoints to set the IPv6 Flow Label field of the network-layer header. As per [RFC6437], IPv6 source nodes "SHOULD assign each unrelated transport connection and application data stream to a new flow." A multiplexing transport could choose to use multiple flow labels to allow the network to independently forward subflows. [RFC6437] provides further guidance on choosing a flow label value, stating these "should be chosen such that their bits exhibit a high degree of variability" and chosen so that "third parties should be unlikely to be able to guess the next value that a source of flow labels will choose."

IPv6ネットワーク層フローラベルの使用:多くの標準トラックと最良の現在の実践RFC(例:[RFC8085]、[RFC6437]、[RFC6438])は、ネットワーク層ヘッダーのIPv6 Flow Labelフィールドを設定するためのエンドポイントを奨励します。。[RFC6437]によると、IPv6ソースノードは、それぞれの無関係なトランスポート接続とアプリケーションデータストリームを新しいフローに割り当てる必要があります。」多重化トランスポートは、ネットワークが独立してサブフローを正しく転送できるように複数のフローラベルを使用することを選択できます。[RFC6437]はフローラベル値を選択することについてのさらなるガイダンスを提供し、「ビットが高い変動性を示すように選択されるべきである」と言って、「第三者は次の値を推測することができないはずではないはずです。フローラベルの発生源は選択されます。」

Once set, a flow label can provide information that can help inform network-layer queueing and forwarding, including use with IPsec [RFC6294], Equal-Cost Multipath routing, and Link Aggregation [RFC6438].

一旦設定されると、フローラベルは、IPsec [RFC6294]、等費マルチパスルーティング、およびリンクアグリゲーション[RFC6438]を含む、ネットワーク層キューイングおよび転送に通知するのに役立つ情報を提供できます。

The choice of how to assign a flow label needs to avoid introducing linkages between flows that a network device could not otherwise observe. Inappropriate use by the transport can have privacy implications (e.g., assigning the same label to two independent flows that ought not to be classified similarly).


Using the Network-Layer Differentiated Services Code Point: Applications can expose their delivery expectations to network devices by setting the Differentiated Services Code Point (DSCP) field of IPv4 and IPv6 packets [RFC2474]. For example, WebRTC applications identify different forwarding treatments for individual subflows (audio vs. video) based on the value of the DSCP field [RFC8837]). This provides explicit information to inform network-layer queueing and forwarding, rather than an operator inferring traffic requirements from transport and application headers via a multi-field classifier. Inappropriate use by the transport can have privacy implications (e.g., assigning a different DSCP to a subflow could assist in a network device discovering the traffic pattern used by an application). The field is mutable, i.e., some network devices can be expected to change this field. Since the DSCP value can impact the quality of experience for a flow, observations of service performance have to consider this field when a network path supports differentiated service treatment.

ネットワーク層の差別化サービスコードポイントを使用すると、アプリケーションはIPv4とIPv6パケットの微分サービスコードポイント(DSCP)フィールドを設定することによって、ネットワークデバイスへの配信期待を公開できます[RFC2474]。たとえば、WebRTCアプリケーションは、DSCPフィールド[RFC8837]の値に基づいて、個々のサブフロー(Audio VS. Video)の異なる転送処理を識別します。これにより、マルチフィールド分類子を介してトランスポートヘッダからトラフィック要件とアプリケーションヘッダからトラフィック要件を推測するのではなく、ネットワーク層キューイングと転送に通知するための明示的な情報が提供されます。トランスポートによる不適切な使用は、プライバシーの意味を持つことができます(例えば、サブフローに異なるDSCPを割り当てることで、アプリケーションによって使用されるトラフィックパターンを発見するのに役立ちます)。このフィールドは、このフィールドを変更することが期待されている場合がある。 DSCP値はフローの経験の質に影響を与える可能性があるため、ネットワークパスが差別化されたサービス処理をサポートしている場合、サービスパフォーマンスの観測はこのフィールドを検討する必要があります。

Using Explicit Congestion Notification: Explicit Congestion Notification (ECN) [RFC3168] is a transport mechanism that uses the ECN field in the network-layer header. Use of ECN explicitly informs the network layer that a transport is ECN capable and requests ECN treatment of the flow. An ECN-capable transport can offer benefits when used over a path with equipment that implements an AQM method with Congestion Experienced (CE) marking of IP packets [RFC8087], since it can react to congestion without also having to recover from lost packets.


ECN exposes the presence of congestion. The reception of CE-marked packets can be used to estimate the level of incipient congestion on the upstream portion of the path from the point of observation (Section 2.5 of [RFC8087]). Interpreting the marking behaviour (i.e., assessing congestion and diagnosing faults) requires context from the transport layer, such as path RTT.


AQM and ECN offer a range of algorithms and configuration options. Tools therefore have to be available to network operators and researchers to understand the implication of configuration choices and transport behaviour as the use of ECN increases and new methods emerge [RFC7567].

AQMとECNは、さまざまなアルゴリズムと設定オプションを提供します。したがって、ECNの増加と新しいメソッドがECNの使用と新しいメソッドがEMERGE [RFC7567]の使用として、ネットワーク事業者や研究者には、ネットワーク事業者や研究者に利用できるようにする必要があります。

Network-Layer Options: Network protocols can carry optional headers (see Section 5.1). These can explicitly expose transport header information to on-path devices operating at the network layer (as discussed further in Section 6).


IPv4 [RFC0791] has provisions for optional header fields. IP routers can examine these headers and are required to ignore IPv4 options that they do not recognise. Many current paths include network devices that forward packets that carry options on a slower processing path. Some network devices (e.g., firewalls) can be (and are) configured to drop these packets [RFC7126]. BCP 186 [RFC7126] provides guidance on how operators should treat IPv4 packets that specify options.

IPv4 [RFC0791]は、オプションのヘッダーフィールドの規定です。IPルータはこれらのヘッダーを調べることができ、認識されないIPv4オプションを無視する必要があります。多くの電流経路は、より遅い処理経路上でオプションを搬送するパケットを転送するネットワークデバイスを含む。これらのパケットをドロップするように構成されているネットワークデバイス(例えば、ファイアウォール)は、(およびRFC7126]を削除するように構成されているものがあります。BCP 186 [RFC7126]オプションを指定するIPv4パケットをどのように扱うかについてのガイダンスを提供します。

IPv6 can encode optional network-layer information in separate headers that may be placed between the IPv6 header and the upper-layer header [RFC8200] (e.g., the IPv6 Alternate Marking Method [IPV6-ALT-MARK], which can be used to measure packet loss and delay metrics). The Hop-by-Hop Options header, when present, immediately follows the IPv6 header. IPv6 permits this header to be examined by any node along the path if explicitly configured [RFC8200].

IPv6は、IPv6ヘッダーと上位レイヤーヘッダー[RFC8200](たとえば、測定に使用できるIPv6代替マーク・メソッド[IPv6 ALT-MARK]など)を別々のヘッダーにエンコードできます。パケット損失と遅延メトリック)ホップバイホップオプションヘッダーが存在する場合は、すぐにIPv6ヘッダーの後に続きます。IPv6は、明示的に設定されている場合[RFC8200]の場合、このヘッダーをパスに沿って任意のノードで調べることができます。

Careful use of the network-layer features (e.g., extension headers can; see Section 5) help provide similar information in the case where the network is unable to inspect transport protocol headers.


2.4. To Support Network Operations
2.4. ネットワーク業務をサポートする

Some network operators make use of on-path observations of transport headers to analyse the service offered to the users of a network segment and inform operational practice and can help detect and locate network problems. [RFC8517] gives an operator's perspective about such use.


When observable transport header information is not available, those seeking an understanding of transport behaviour and dynamics might learn to work without that information. Alternatively, they might use more limited measurements combined with pattern inference and other heuristics to infer network behaviour (see Section 2.1.1 of [RFC8404]). Operational practises aimed at inferring transport parameters are out of scope for this document and are only mentioned here to recognise that encryption does not necessarily stop operators from attempting to apply practises that have been used with unencrypted transport headers.


This section discusses topics concerning observation of transport flows, with a focus on transport measurement.


2.4.1. Problem Location
2.4.1. 問題の場所

Observations of transport header information can be used to locate the source of problems or to assess the performance of a network segment. Often issues can only be understood in the context of the other flows that share a particular path, particular device configuration, interface port, etc. A simple example is monitoring of a network device that uses a scheduler or active queue management technique [RFC7567], where it could be desirable to understand whether the algorithms are correctly controlling latency or if overload protection is working. This implies knowledge of how traffic is assigned to any subqueues used for flow scheduling but can require information about how the traffic dynamics impact active queue management, starvation prevention mechanisms, and circuit breakers.


Sometimes correlating observations of headers at multiple points along the path (e.g., at the ingress and egress of a network segment) allows an observer to determine the contribution of a portion of the path to an observed metric (e.g., to locate a source of delay, jitter, loss, reordering, or congestion marking).


2.4.2. Network Planning and Provisioning
2.4.2. ネットワーク計画とプロビジョニング

Traffic rate and volume measurements are used to help plan deployment of new equipment and configuration in networks. Data is also valuable to equipment vendors who want to understand traffic trends and patterns of usage as inputs to decisions about planning products and provisioning for new deployments.


Trends in aggregate traffic can be observed and can be related to the endpoint addresses being used, but when transport header information is not observable, it might be impossible to correlate patterns in measurements with changes in transport protocols. This increases the dependency on other indirect sources of information to inform planning and provisioning.


2.4.3. Compliance with Congestion Control
2.4.3. 輻輳制御への準拠

The traffic that can be observed by on-path network devices (the "wire image") is a function of transport protocol design/options, network use, applications, and user characteristics. In general, when only a small proportion of the traffic has a specific (different) characteristic, such traffic seldom leads to operational concern, although the ability to measure and monitor it is lower. The desire to understand the traffic and protocol interactions typically grows as the proportion of traffic increases. The challenges increase when multiple instances of an evolving protocol contribute to the traffic that share network capacity.


Operators can manage traffic load (e.g., when the network is severely overloaded) by deploying rate limiters, traffic shaping, or network transport circuit breakers [RFC8084]. The information provided by observing transport headers is a source of data that can help to inform such mechanisms.


Congestion Control Compliance of Traffic: Congestion control is a key transport function [RFC2914]. Many network operators implicitly accept that TCP traffic complies with a behaviour that is acceptable for the shared Internet. TCP algorithms have been continuously improved over decades and have reached a level of efficiency and correctness that is difficult to match in custom application-layer mechanisms [RFC8085].


A standards-compliant TCP stack provides congestion control that is judged safe for use across the Internet. Applications developed on top of well-designed transports can be expected to appropriately control their network usage, reacting when the network experiences congestion, by backing off and reducing the load placed on the network. This is the normal expected behaviour for IETF-specified transports (e.g., TCP and SCTP).


Congestion Control Compliance for UDP Traffic: UDP provides a minimal message-passing datagram transport that has no inherent congestion control mechanisms. Because congestion control is critical to the stable operation of the Internet, applications and other protocols that choose to use UDP as a transport have to employ mechanisms to prevent collapse, avoid unacceptable contributions to jitter/latency, and establish an acceptable share of capacity with concurrent traffic [RFC8085].


UDP flows that expose a well-known header can be observed to gain understanding of the dynamics of a flow and its congestion control behaviour. For example, tools exist to monitor various aspects of RTP header information and RTCP reports for real-time flows (see Section 2.3). The Secure RTP and RTCP extensions [RFC3711] were explicitly designed to expose some header information to enable such observation while protecting the payload data.

よく知られているヘッダーを露出させるUDPフローは、流れのダイナミクスとその輻輳制御の行動を理解するために観察されます。たとえば、RTPヘッダー情報とRTCPレポートのリアルタイムフローのさまざまな側面を監視するためのツールが存在します(セクション2.3を参照)。セキュアRTPおよびRTCP Extensions [RFC3711]は、ペイロードデータを保護しながらこのような観察を可能にするためにいくつかのヘッダー情報を公開するように明示的に設計されていました。

A network operator can observe the headers of transport protocols layered above UDP to understand if the datagram flows comply with congestion control expectations. This can help inform a decision on whether it might be appropriate to deploy methods, such as rate limiters, to enforce acceptable usage. The available information determines the level of precision with which flows can be classified and the design space for conditioning mechanisms (e.g., rate-limiting, circuit breaker techniques [RFC8084], or blocking uncharacterised traffic) [RFC5218].


When anomalies are detected, tools can interpret the transport header information to help understand the impact of specific transport protocols (or protocol mechanisms) on the other traffic that shares a network. An observer on the network path can gain an understanding of the dynamics of a flow and its congestion control behaviour. Analysing observed flows can help to build confidence that an application flow backs off its share of the network load under persistent congestion and hence to understand whether the behaviour is appropriate for sharing limited network capacity. For example, it is common to visualise plots of TCP sequence numbers versus time for a flow to understand how a flow shares available capacity, deduce its dynamics in response to congestion, etc.


The ability to identify sources and flows that contribute to persistent congestion is important to the safe operation of network infrastructure and can inform configuration of network devices to complement the endpoint congestion avoidance mechanisms [RFC7567] [RFC8084] to avoid a portion of the network being driven into congestion collapse [RFC2914].

永続的な輻輳に貢献する情報源と流れを識別する能力は、ネットワークインフラストラクチャの安全な操作にとって重要であり、ネットワークの一部を駆動することを避けるために、エンドポイント輻輳回避メカニズム[RFC7567] [RFC8084]を補完するためのネットワークデバイスの構成を知らせることができます。輻輳崩壊[RFC2914]。

2.4.4. To Characterise "Unknown" Network Traffic
2.4.4. 「不明」ネットワークトラフィックを特徴付けるには

The patterns and types of traffic that share Internet capacity change over time as networked applications, usage patterns, and protocols continue to evolve.


Encryption can increase the volume of "unknown" or "uncharacterised" traffic seen by the network. If these traffic patterns form a small part of the traffic aggregate passing through a network device or segment of the network path, the dynamics of the uncharacterised traffic might not have a significant collateral impact on the performance of other traffic that shares this network segment. Once the proportion of this traffic increases, monitoring the traffic can determine if appropriate safety measures have to be put in place.


Tracking the impact of new mechanisms and protocols requires traffic volume to be measured and new transport behaviours to be identified. This is especially true of protocols operating over a UDP substrate. The level and style of encryption needs to be considered in determining how this activity is performed.


Traffic that cannot be classified typically receives a default treatment. Some networks block or rate-limit traffic that cannot be classified.


2.4.5. To Support Network Security Functions
2.4.5. ネットワークセキュリティ機能をサポートする

On-path observation of the transport headers of packets can be used for various security functions. For example, Denial of Service (DoS) and Distributed DoS (DDoS) attacks against the infrastructure or against an endpoint can be detected and mitigated by characterising anomalous traffic (see Section 2.4.4) on a shorter timescale. Other uses include support for security audits (e.g., verifying the compliance with cipher suites), client and application fingerprinting for inventory, and alerts provided for network intrusion detection and other next generation firewall functions.


When using an encrypted transport, endpoints can directly provide information to support these security functions. Another method, if the endpoints do not provide this information, is to use an on-path network device that relies on pattern inferences in the traffic and heuristics or machine learning instead of processing observed header information. An endpoint could also explicitly cooperate with an on-path device (e.g., a QUIC endpoint could share information about current uses of connection IDs).


2.4.6. Network Diagnostics and Troubleshooting
2.4.6. ネットワーク診断とトラブルシューティング

Operators monitor the health of a network segment to support a variety of operational tasks [RFC8404], including procedures to provide early warning and trigger action, e.g., to diagnose network problems, to manage security threats (including DoS), to evaluate equipment or protocol performance, or to respond to user performance questions. Information about transport flows can assist in setting buffer sizes and help identify whether link/network tuning is effective. Information can also support debugging and diagnosis of the root causes of faults that concern a particular user's traffic and can support postmortem investigation after an anomaly. Sections 3.1.2 and 5 of [RFC8404] provide further examples.


Network segments vary in their complexity. The design trade-offs for radio networks are often very different from those of wired networks [RFC8462]. A radio-based network (e.g., cellular mobile, enterprise Wireless LAN (WLAN), satellite access/backhaul, point-to-point radio) adds a subsystem that performs radio resource management, with impact on the available capacity and potentially loss/reordering of packets. This impact can differ by traffic type and can be correlated with link propagation and interference. These can impact the cost and performance of a provided service and is expected to increase in importance as operators bring together heterogeneous types of network equipment and deploy opportunistic methods to access a shared radio spectrum.


2.4.7. Tooling and Network Operations
2.4.7. ツーリングとネットワーク操作

A variety of open source and proprietary tools have been deployed that use the transport header information observable with widely used protocols, such as TCP or RTP/UDP/IP. Tools that dissect network traffic flows can alert to potential problems that are hard to derive from volume measurements, link statistics, or device measurements alone.

TCPまたはRTP / UDP / IPなどの広く使用されているプロトコルで観測できるトランスポートヘッダ情報を使用するさまざまなオープンソースおよび独自のツールが展開されています。ネットワークトラフィックフローを解析するツールは、音量測定、リンク統計、またはデバイス測定だけから導きにくい潜在的な問題に警告することができます。

Any introduction of a new transport protocol, protocol feature, or application might require changes to such tools and could impact operational practice and policies. Such changes have associated costs that are incurred by the network operators that need to update their tooling or develop alternative practises that work without access to the changed/removed information.


The use of encryption has the desirable effect of preventing unintended observation of the payload data, and these tools seldom seek to observe the payload or other application details. A flow that hides its transport header information could imply "don't touch" to some operators. This might limit a trouble-shooting response to "can't help, no trouble found".


An alternative that does not require access to an observable transport headers is to access endpoint diagnostic tools or to include user involvement in diagnosing and troubleshooting unusual use cases or to troubleshoot nontrivial problems. Another approach is to use traffic pattern analysis. Such tools can provide useful information during network anomalies (e.g., detecting significant reordering, high or intermittent loss); however, indirect measurements need to be carefully designed to provide information for diagnostics and troubleshooting.


If new protocols, or protocol extensions, are made to closely resemble or match existing mechanisms, then the changes to tooling and the associated costs can be small. Equally, more extensive changes to the transport tend to require more extensive, and more expensive, changes to tooling and operational practice. Protocol designers can mitigate these costs by explicitly choosing to expose selected information as invariants that are guaranteed not to change for a particular protocol (e.g., the header invariants and the spin bit in QUIC [RFC9000]). Specification of common log formats and development of alternative approaches can also help mitigate the costs of transport changes.

新しいプロトコル、またはプロトコル拡張機能が既存のメカニズムに密接に似ているか一致させるようにされた場合、ツーリングへの変更および関連コストは小さくなる可能性があります。同様に、輸送へのより広範な変化は、より広範な、そしてより高価で、ツーリングおよび運用慣行の変化を必要とする傾向がある。プロトコル設計者は、特定のプロトコル(例えば、ヘッダ不変式およびQUIC [RFC9000]のスピンビット)について変更しないことを保証する不変式として、選択された情報を公開することを明示的に選択することによってこれらのコストを軽減することができる。一般的なログフォーマットの指定と代替アプローチの開発はまた、トランスポートの変更のコストを軽減するのに役立ちます。

2.5. To Mitigate the Effects of Constrained Networks
2.5. 制約されたネットワークの影響を軽減するため

Some link and network segments are constrained by the capacity they can offer by the time it takes to access capacity (e.g., due to underlying radio resource management methods) or by asymmetries in the design (e.g., many link are designed so that the capacity available is different in the forward and return directions; some radio technologies have different access methods in the forward and return directions resulting from differences in the power budget).


The impact of path constraints can be mitigated using a proxy operating at or above the transport layer to use an alternate transport protocol.


In many cases, one or both endpoints are unaware of the characteristics of the constraining link or network segment, and mitigations are applied below the transport layer. Packet classification and QoS methods (described in various sections) can be beneficial in differentially prioritising certain traffic when there is a capacity constraint or additional delay in scheduling link transmissions. Another common mitigation is to apply header compression over the specific link or subnetwork (see Section 2.5.1).


2.5.1. To Provide Header Compression
2.5.1. ヘッダー圧縮を提供する

Header compression saves link capacity by compressing network and transport protocol headers on a per-hop basis. This has been widely used with low bandwidth dial-up access links and still finds application on wireless links that are subject to capacity constraints. These methods are effective for bit-congestive links sending small packets (e.g., reducing the cost for sending control packets or small data packets over radio links).


Examples of header compression include use with TCP/IP and RTP/UDP/IP flows [RFC2507] [RFC6846] [RFC2508] [RFC5795] [RFC8724]. Successful compression depends on observing the transport headers and understanding the way fields change between packets and is hence incompatible with header encryption. Devices that compress transport headers are dependent on a stable header format, implying ossification of that format.

ヘッダ圧縮の例には、TCP / IPおよびRTP / UDP / IPフローでの使用が含まれます[RFC2507] [RFC6846] [RFC2508] [RFC5795] [RFC8724]。圧縮が成功すると、トランスポートヘッダの監視とパケット間のフィールドの変化方法を理解することによって異なります。したがって、ヘッダー暗号化と互換性がありません。トランスポートヘッダを圧縮する装置は安定したヘッダフォーマットに依存し、そのフォーマットの骨化を意味します。

Introducing a new transport protocol, or changing the format of the transport header information, will limit the effectiveness of header compression until the network devices are updated. Encrypting the transport protocol headers will tend to cause the header compression to fall back to compressing only the network-layer headers, with a significant reduction in efficiency. This can limit connectivity if the resulting flow exceeds the link capacity or if the packets are dropped because they exceed the link Maximum Transmission Unit (MTU).


The Secure RTP (SRTP) extensions [RFC3711] were explicitly designed to leave the transport protocol headers unencrypted, but authenticated, since support for header compression was considered important.

SECURE RTP(SRTP)拡張[RFC3711]は、トランスポートプロトコルヘッダを暗号化されていないが、ヘッダ圧縮のサポートが重要であると考えられているため、明示的に設計されていました。

2.6. To Verify SLA Compliance
2.6. SLAコンプライアンスを検証する

Observable transport headers coupled with published transport specifications allow operators and regulators to explore and verify compliance with Service Level Agreements (SLAs). It can also be used to understand whether a service is providing differential treatment to certain flows.


When transport header information cannot be observed, other methods have to be found to confirm that the traffic produced conforms to the expectations of the operator or developer.


Independently verifiable performance metrics can be utilised to demonstrate regulatory compliance in some jurisdictions and as a basis for informing design decisions. This can bring assurance to those operating networks, often avoiding deployment of complex techniques that routinely monitor and manage Internet traffic flows (e.g., avoiding the capital and operational costs of deploying flow rate-limiting and network circuit breaker methods [RFC8084]).


3. Research, Development, and Deployment
3. 研究、開発、および展開

Research and development of new protocols and mechanisms need to be informed by measurement data (as described in the previous section). Data can also help promote acceptance of proposed standards specifications by the wider community (e.g., as a method to judge the safety for Internet deployment).


Observed data is important to ensure the health of the research and development communities and provides data needed to evaluate new proposals for standardisation. Open standards motivate a desire to include independent observation and evaluation of performance and deployment data. Independent data helps compare different methods, judge the level of deployment, and ensure the wider applicability of the results. This is important when considering when a protocol or mechanism should be standardised for use in the general Internet. This, in turn, demands control/understanding about where and when measurement samples are collected. This requires consideration of the methods used to observe information and the appropriate balance between encrypting all and no transport header information.


There can be performance and operational trade-offs in exposing selected information to network tools. This section explores key implications of tools and procedures that observe transport protocols but does not endorse or condemn any specific practises.


3.1. Independent Measurement
3.1. 独立した測定

Encrypting transport header information has implications on the way network data is collected and analysed. Independent observations by multiple actors is currently used by the transport community to maintain an accurate understanding of the network within transport area working groups, IRTF research groups, and the broader research community. This is important to be able to provide accountability and demonstrate that protocols behave as intended; although, when providing or using such information, it is important to consider the privacy of the user and their incentive for providing accurate and detailed information.


Protocols that expose the state of the transport protocol in their header (e.g., timestamps used to calculate the RTT, packet numbers used to assess congestion, and requests for retransmission) provide an incentive for a sending endpoint to provide consistent information, because a protocol will not work otherwise. An on-path observer can have confidence that well-known (and ossified) transport header information represents the actual state of the endpoints when this information is necessary for the protocol's correct operation.


Encryption of transport header information could reduce the range of actors that can observe useful data. This would limit the information sources available to the Internet community to understand the operation of new transport protocols, reducing information to inform design decisions and standardisation of the new protocols and related operational practises. The cooperating dependence of network, application, and host to provide communication performance on the Internet is uncertain when only endpoints (i.e., at user devices and within service platforms) can observe performance and when performance cannot be independently verified by all parties.


3.2. Measurable Transport Protocols
3.2. 測定可能な輸送プロトコル

Transport protocol evolution and the ability to measure and understand the impact of protocol changes have to proceed hand-in-hand. A transport protocol that provides observable headers can be used to provide open and verifiable measurement data. Observation of pathologies has a critical role in the design of transport protocol mechanisms and development of new mechanisms and protocols and aides in understanding the interactions between cooperating protocols and network mechanisms, the implications of sharing capacity with other traffic, and the impact of different patterns of usage. The ability of other stakeholders to review transport header traces helps develop insight into the performance and the traffic contribution of specific variants of a protocol.


Development of new transport protocol mechanisms has to consider the scale of deployment and the range of environments in which the transport is used. Experience has shown that it is often difficult to correctly implement new mechanisms [RFC8085] and that mechanisms often evolve as a protocol matures or in response to changes in network conditions, in network traffic, or to application usage. Analysis is especially valuable when based on the behaviour experienced across a range of topologies, vendor equipment, and traffic patterns.


Encryption enables a transport protocol to choose which internal state to reveal to devices on the network path, what information to encrypt, and what fields to grease [RFC8701]. A new design can provide summary information regarding its performance, congestion control state, etc., or make explicit measurement information available. For example, [RFC9000] specifies a way for a QUIC endpoint to optionally set the spin bit to explicitly reveal the RTT of an encrypted transport session to the on-path network devices. There is a choice of what information to expose. For some operational uses, the information has to contain sufficient detail to understand, and possibly reconstruct, the network traffic pattern for further testing. The interpretation of the information needs to consider whether this information reflects the actual transport state of the endpoints. This might require the trust of transport protocol implementers to correctly reveal the desired information.


New transport protocol formats are expected to facilitate an increased pace of transport evolution and with it the possibility to experiment with and deploy a wide range of protocol mechanisms. At the time of writing, there has been interest in a wide range of new transport methods, e.g., larger initial window, Proportional Rate Reduction (PRR), congestion control methods based on measuring bottleneck bandwidth and round-trip propagation time, the introduction of AQM techniques, and new forms of ECN response (e.g., Data Centre TCP, DCTCP, and methods proposed for Low Latency Low Loss Scalable throughput (L4S)). The growth and diversity of applications and protocols using the Internet also continues to expand. For each new method or application, it is desirable to build a body of data reflecting its behaviour under a wide range of deployment scenarios, traffic load, and interactions with other deployed/candidate methods.


3.3. Other Sources of Information
3.3. その他の情報源

Some measurements that traditionally rely on observable transport information could be completed by utilising endpoint-based logging (e.g., based on QUIC trace [Quic-Trace] and qlog [QLOG]). Such information has a diversity of uses, including developers wishing to debug/understand the transport/application protocols with which they work, researchers seeking to spot trends and anomalies, and to characterise variants of protocols. A standard format for endpoint logging could allow these to be shared (after appropriate anonymisation) to understand performance and pathologies.

特定の輸送情報に伝統的に依存するいくつかの測定値は、エンドポイントベースのログ記録(例えば、QUICトレース[QLACE [QLOG [QLOG]に基づく)を利用することによって完了することができる。そのような情報には、動向や異常を見つけ、プロトコルの変種を特徴付ける研究者が働く、研究者が働く、研究者たちは、開発者を含む開発者を含む多様な用途があります。エンドポイントロギングの標準形式では、パフォーマンスとパスロジーを理解するためにこれらを(適切な匿名化後)共有することができます。

When measurement datasets are made available by servers or client endpoints, additional metadata, such as the state of the network and conditions in which the system was observed, is often necessary to interpret this data to answer questions about network performance or understand a pathology. Collecting and coordinating such metadata is more difficult when the observation point is at a different location to the bottleneck or device under evaluation [RFC7799].


Despite being applicable in some scenarios, endpoint logs do not provide equivalent information to on-path measurements made by devices in the network. In particular, endpoint logs contain only a part of the information to understand the operation of network devices and identify issues, such as link performance or capacity sharing between multiple flows. An analysis can require coordination between actors at different layers to successfully characterise flows and correlate the performance or behaviour of a specific mechanism with an equipment configuration and traffic using operational equipment along a network path (e.g., combining transport and network measurements to explore congestion control dynamics to understand the implications of traffic on designs for active queue management or circuit breakers).


Another source of information could arise from Operations, Administration, and Maintenance (OAM) (see Section 6). Information data records could be embedded into header information at different layers to support functions, such as performance evaluation, path tracing, path verification information, classification, and a diversity of other uses.


In-situ OAM (IOAM) data fields [IOAM-DATA] can be encapsulated into a variety of protocols to record operational and telemetry information in an existing packet while that packet traverses a part of the path between two points in a network (e.g., within a particular IOAM management domain). IOAM-Data-Fields are independent from the protocols into which IOAM-Data-Fields are encapsulated. For example, IOAM can provide proof that a traffic flow takes a predefined path, SLA verification for the live data traffic, and statistics relating to traffic distribution.

その場でのOAM(IOAM)データフィールド[IOAM - DATA]を様々なプロトコルにカプセル化することができ、そのパケットはネットワーク内の2つの点間の経路の一部を通過しながら、既存のパケット内の操作上およびテレメトリ情報を記録することができる(例えば、特定のIOAM管理ドメイン内)。IOAMデータフィールドは、IOAMデータフィールドがカプセル化されているプロトコルから独立しています。たとえば、IOAMは、トラフィックフローが事前定義されたパス、ライブデータトラフィックのSLA検証、およびトラフィック分布に関する統計を取ります。

4. Encryption and Authentication of Transport Headers
4. トランスポートヘッダの暗号化と認証

There are several motivations for transport header encryption.


One motive to encrypt transport headers is to prevent network ossification from network devices that inspect well-known transport headers. Once a network device observes a transport header and becomes reliant upon using it, the overall use of that field can become ossified, preventing new versions of the protocol and mechanisms from being deployed. Examples include:


* During the development of TLS 1.3 [RFC8446], the design needed to function in the presence of deployed middleboxes that relied on the presence of certain header fields exposed in TLS 1.2 [RFC5426].

* TLS 1.3 [RFC8446]の開発中に、TLS 1.2 [RFC5426]で公開されている特定のヘッダーフィールドの存在に依存しているデプロイされたミドルボックスの存在下で機能するのに必要な設計が必要です。

* The design of Multipath TCP (MPTCP) [RFC8684] had to account for middleboxes (known as "TCP Normalizers") that monitor the evolution of the window advertised in the TCP header and then reset connections when the window did not grow as expected.

* Multipath TCP(MPTCP)[RFC8684]の設計は、TCPヘッダーでアドバタイズされたウィンドウの進化を監視し、ウィンドウが予想どおりに成長しなかったときに接続をリセットするミドルボックス(「TCPノーマル」として知られていました)を考慮しなければなりませんでした。

* TCP Fast Open [RFC7413] can experience problems due to middleboxes that modify the transport header of packets by removing "unknown" TCP options. Segments with unrecognised TCP options can be dropped, segments that contain data and set the SYN bit can be dropped, and some middleboxes that disrupt connections can send data before completion of the three-way handshake.

* TCP Fast Open [RFC7413]は、「不明な」TCPオプションを削除することで、パケットのトランスポートヘッダを変更するミドルボックスが発生する可能性があります。認識されないTCPオプションを持つセグメントを削除することができ、データを含むセグメント、SYNビットを削除することができ、接続を中断するミドルボックスが3方向ハンドシェイクの完了前にデータを送信できます。

* Other examples of TCP ossification have included middleboxes that modify transport headers by rewriting TCP sequence and acknowledgement numbers but are unaware of the (newer) TCP selective acknowledgement (SACK) option and therefore fail to correctly rewrite the SACK information to match the changes made to the fixed TCP header, preventing correct SACK operation.

* TCP骨化の他の例には、TCPシーケンスおよび確認応答番号を書き換えることによってトランスポートヘッダを変更するミドルボックスが含まれていますが、(新しい)TCP選択認識(SACK)オプションを認識していないため、SACK情報を正しく書き換えることができ、TCPヘッダーを修正し、正しい袋の操作を防ぎます。

In all these cases, middleboxes with a hard-coded, but incomplete, understanding of a specific transport behaviour (i.e., TCP) interacted poorly with transport protocols after the transport behaviour was changed. In some cases, the middleboxes modified or replaced information in the transport protocol header.


Transport header encryption prevents an on-path device from observing the transport headers and therefore stops ossified mechanisms being used that directly rely on or infer semantics of the transport header information. This encryption is normally combined with authentication of the protected information. [RFC8546] summarises this approach, stating that "[t]he wire image, not the protocol's specification, determines how third parties on the network paths among protocol participants will interact with that protocol" (Section 1 of [RFC8546]), and it can be expected that header information that is not encrypted will become ossified.


Encryption does not itself prevent ossification of the network service. People seeking to understand or classify network traffic could still come to rely on pattern inferences and other heuristics or machine learning to derive measurement data and as the basis for network forwarding decisions [RFC8546]. This can also create dependencies on the transport protocol or the patterns of traffic it can generate, also resulting in ossification of the service.


Another motivation for using transport header encryption is to improve privacy and to decrease opportunities for surveillance. Users value the ability to protect their identity and location and defend against analysis of the traffic. Revelations about the use of pervasive surveillance [RFC7624] have, to some extent, eroded trust in the service offered by network operators and have led to an increased use of encryption. Concerns have also been voiced about the addition of metadata to packets by third parties to provide analytics, customisation, advertising, cross-site tracking of users, customer billing, or selectively allowing or blocking content.

トランスポートヘッダ暗号化を使用するための別の動機は、プライバシーを向上させ、監視の機会を減らすことです。ユーザーは、自分のアイデンティティと場所を保護し、トラフィックの分析に対して守る能力を評価します。Pervasive Surveillance [RFC7624]の使用に関する啓示はある程度、ネットワーク事業者によって提供されるサービス内の侵食された信頼を持っており、暗号化の使用の増加につながっています。また、第三者によるパケットへのメタデータの追加については、ユーザーの分析、カスタマイズ、広告、クロスサイトの追跡、またはコンテンツを選択的に許可またはブロックすることについてのメタデータを追加しました。

Whatever the reasons, the IETF is designing protocols that include transport header encryption (e.g., QUIC [RFC9000]) to supplement the already widespread payload encryption and to further limit exposure of transport metadata to the network.

その理由が決して、IETFは、すでに広範囲のペイロード暗号化を補完するためのトランスポートヘッダー暗号化(例えば、QUIC [RFC9000])を含むプロトコルを設計し、トランスポートメタデータのネットワークへのエクスポージャーをさらに制限します。

If a transport protocol uses header encryption, the designers have to decide whether to encrypt all or a part of the transport-layer information. Section 4 of [RFC8558] states, "Anything exposed to the path should be done with the intent that it be used by the network elements on the path."


Certain transport header fields can be made observable to on-path network devices or can define new fields designed to explicitly expose observable transport-layer information to the network. Where exposed fields are intended to be immutable (i.e., can be observed but not modified by a network device), the endpoints are encouraged to use authentication to provide a cryptographic integrity check that can detect if these immutable fields have been modified by network devices. Authentication can help to prevent attacks that rely on sending packets that fake exposed control signals in transport headers (e.g., TCP RST spoofing). Making a part of a transport header observable or exposing new header fields can lead to ossification of that part of a header as network devices come to rely on observations of the exposed fields.

特定のトランスポートヘッダフィールドは、オンパスネットワークデバイスに対して観察可能になり、観測可能なトランスポート層情報をネットワークに明示的に公開するように設計された新しいフィールドを定義できます。露出したフィールドが不変であることを意図している場合(すなわち、ネットワークデバイスによって観察されないが、ネットワークデバイスによって修正されない)ことが意図されている場合、エンドポイントは、これらの不変フィールドがネットワークデバイスによって修正されているかどうかを検出することができる暗号化完全性チェックを提供するために認証を使用することが奨励される。認証は、トランスポートヘッダ(例えば、TCP RSTスプーフィング)で露出した制御信号を偽造するパケットの送信に依存する攻撃を防ぐのに役立ちます。トランスポートヘッダの一部を観察可能または露光すること、または新しいヘッダフィールドを露出させることは、ネットワークデバイスが露光されたフィールドの観察に頼るようにヘッダのその部分の骨化をもたらす可能性がある。

The use of transport header authentication and encryption therefore exposes a tussle between middlebox vendors, operators, researchers, applications developers, and end users:


* On the one hand, future Internet protocols that support transport header encryption assist in the restoration of the end-to-end nature of the Internet by returning complex processing to the endpoints. Since middleboxes cannot modify what they cannot see, the use of transport header encryption can improve application and end-user privacy by reducing leakage of transport metadata to operators that deploy middleboxes.

* 一方では、トランスポートヘッダ暗号化をサポートする将来のインターネットプロトコルは、複雑な処理をエンドポイントに返すことによって、インターネットのエンドツーエンドの性質の復元を支援します。ミドルボックスが表示できないものを変更できないので、トランスポートヘッダー暗号化の使用は、ミドルボックスを展開する演算子へのトランスポートメタデータの漏洩を減らすことによって、アプリケーションとエンドユーザーのプライバシーを向上させることができます。

* On the other hand, encryption of transport-layer information has implications for network operators and researchers seeking to understand the dynamics of protocols and traffic patterns, since it reduces the information that is available to them.

* 一方、トランスポート層情報の暗号化は、ネットワーク事業者や研究者にとって、利用可能な情報を縮小するため、プロトコルとトラフィックパターンのダイナミクスを理解しようとしている研究者にとっての影響を受けています。

The following briefly reviews some security design options for transport protocols. "A Survey of the Interaction between Security Protocols and Transport Services" [RFC8922] provides more details concerning commonly used encryption methods at the transport layer.


Security work typically employs a design technique that seeks to expose only what is needed [RFC3552]. This approach provides incentives to not reveal any information that is not necessary for the end-to-end communication. The IETF has provided guidelines for writing security considerations for IETF specifications [RFC3552].


Endpoint design choices impacting privacy also need to be considered as a part of the design process [RFC6973]. The IAB has provided guidance for analysing and documenting privacy considerations within IETF specifications [RFC6973].


Authenticating the Transport Protocol Header: Transport-layer header information can be authenticated. An example transport authentication mechanism is TCP Authentication Option (TCP-AO) [RFC5925]. This TCP option authenticates the IP pseudo-header, TCP header, and TCP data. TCP-AO protects the transport layer, preventing attacks from disabling the TCP connection itself and provides replay protection. Such authentication might interact with middleboxes, depending on their behaviour [RFC3234].


The IPsec Authentication Header (AH) [RFC4302] was designed to work at the network layer and authenticate the IP payload. This approach authenticates all transport headers and verifies their integrity at the receiver, preventing modification by network devices on the path. The IPsec Encapsulating Security Payload (ESP) [RFC4303] can also provide authentication and integrity without confidentiality using the NULL encryption algorithm [RFC2410]. SRTP [RFC3711] is another example of a transport protocol that allows header authentication.

IPsec認証ヘッダー(AH)[RFC4302]は、ネットワーク層で動作してIPペイロードを認証するように設計されていました。このアプローチは、すべてのトランスポートヘッダーを認証し、受信機での完全性を検証し、パス上のネットワークデバイスによる変更を防ぎます。Security Payload(ESP)[RFC4303]をカプセル化するIPsecは、NULL暗号化アルゴリズム[RFC2410]を使用して、機密性なく認証と整合性を提供できます。SRTP [RFC3711]は、ヘッダー認証を可能にするトランスポートプロトコルのもう1つの例です。

Integrity Check: Transport protocols usually employ integrity checks on the transport header information. Security methods usually employ stronger checks and can combine this with authentication. An integrity check that protects the immutable transport header fields, but can still expose the transport header information in the clear, allows on-path network devices to observe these fields. An integrity check is not able to prevent modification by network devices on the path but can prevent a receiving endpoint from accepting changes and avoid impact on the transport protocol operation, including some types of attack.


Selectively Encrypting Transport Headers and Payload: A transport protocol design that encrypts selected header fields allows specific transport header fields to be made observable by network devices on the path. This information is explicitly exposed either in a transport header field or lower layer protocol header. A design that only exposes immutable fields can also perform end-to-end authentication of these fields across the path to prevent undetected modification of the immutable transport headers.


Mutable fields in the transport header provide opportunities where on-path network devices can modify the transport behaviour (e.g., the extended headers described in [PLUS-ABSTRACT-MECH]). An example of a method that encrypts some, but not all, transport header information is GRE-in-UDP [RFC8086] when used with GRE encryption.

トランスポートヘッダ内の可変フィールドは、オンパスネットワークデバイスがトランスポート動作を変更できる機会(例えば、[プラス抽象メック]に記載されている拡張ヘッダ])を提供する。GRE暗号化で使用すると、ALLを暗号化する方法の例では、トランスポートヘッダー情報はGRE-IN-UDP [RFC8086]です。

Optional Encryption of Header Information: There are implications to the use of optional header encryption in the design of a transport protocol, where support of optional mechanisms can increase the complexity of the protocol and its implementation and in the management decisions that have to be made to use variable format fields. Instead, fields of a specific type ought to be sent with the same level of confidentiality or integrity protection.


Greasing: Protocols often provide extensibility features, reserving fields or values for use by future versions of a specification. The specification of receivers has traditionally ignored unspecified values; however, on-path network devices have emerged that ossify to require a certain value in a field or reuse a field for another purpose. When the specification is later updated, it is impossible to deploy the new use of the field and forwarding of the protocol could even become conditional on a specific header field value.


A protocol can intentionally vary the value, format, and/or presence of observable transport header fields at random [RFC8701]. This prevents a network device ossifying the use of a specific observable field and can ease future deployment of new uses of the value or code point. This is not a security mechanism, although the use can be combined with an authentication mechanism.


Different transports use encryption to protect their header information to varying degrees. The trend is towards increased protection.


5. Intentionally Exposing Transport Information to the Network
5. 意図的にトランスポート情報をネットワークに公開する

A transport protocol can choose to expose certain transport information to on-path devices operating at the network layer by sending observable fields. One approach is to make an explicit choice not to encrypt certain transport header fields, making this transport information observable by an on-path network device. Another approach is to expose transport information in a network-layer extension header (see Section 5.1). Both are examples of explicit information intended to be used by network devices on the path [RFC8558].


Whatever the mechanism used to expose the information, a decision to expose only specific information places the transport endpoint in control of what to expose outside of the encrypted transport header. This decision can then be made independently of the transport protocol functionality. This can be done by exposing part of the transport header or as a network-layer option/extension.


5.1. Exposing Transport Information in Extension Headers
5.1. 拡張ヘッダ内のトランスポート情報を公開する

At the network layer, packets can carry optional headers that explicitly expose transport header information to the on-path devices operating at the network layer (Section 2.3.2). For example, an endpoint that sends an IPv6 hop-by-hop option [RFC8200] can provide explicit transport-layer information that can be observed and used by network devices on the path. New hop-by-hop options are not recommended in [RFC8200] "because nodes may be configured to ignore the Hop-by-Hop Options header, drop packets containing a Hop-by-Hop Options header, or assign packets containing a Hop-by-Hop Options header to a slow processing path. Designers considering defining new hop-by-hop options need to be aware of this likely behavior."


Network-layer optional headers explicitly indicate the information that is exposed, whereas use of exposed transport header information first requires an observer to identify the transport protocol and its format. See Section 2.2.


An arbitrary path can include one or more network devices that drop packets that include a specific header or option used for this purpose (see [RFC7872]). This could impact the proper functioning of the protocols using the path. Protocol methods can be designed to probe to discover whether the specific option(s) can be used along the current path, enabling use on arbitrary paths.


5.2. Common Exposed Transport Information
5.2. 一般的な露出輸送情報

There are opportunities for multiple transport protocols to consistently supply common observable information [RFC8558]. A common approach can result in an open definition of the observable fields. This has the potential that the same information can be utilised across a range of operational and analysis tools.


5.3. Considerations for Exposing Transport Information
5.3. 輸送情報を公開するための考慮事項

Considerations concerning what information, if any, it is appropriate to expose include:


* On the one hand, explicitly exposing derived fields containing relevant transport information (e.g., metrics for loss, latency, etc.) can avoid network devices needing to derive this information from other header fields. This could result in development and evolution of transport-independent tools around a common observable header and permit transport protocols to also evolve independently of this ossified header [RFC8558].

* 一方では、関連するトランスポート情報を含む派生フィールド(例えば、損失、待ち時間など)を含む派生フィールドを明示的に露出させることは、他のヘッダフィールドからこの情報を導出する必要があるネットワークデバイスを回避することができる。これは、共通の観察可能なヘッダーの周りの輸送に依存しないツールの開発と進化をもたらし、この骨董品のヘッダー[RFC8558]とは無関係に進化するように移送プロトコルを許可する可能性があります。

* On the other hand, protocols and implementations might be designed to avoid consistently exposing external information that corresponds to the actual internal information used by the protocol itself. An endpoint/protocol could choose to expose transport header information to optimise the benefit it gets from the network [RFC8558]. The value of this information for analysing operation of the transport layer would be enhanced if the exposed information could be verified to match the transport protocol's observed behavior.

* 一方、プロトコルと実装は、プロトコル自体によって使用される実際の内部情報に対応する外部情報を一貫して公開するように設計されている可能性があります。エンドポイント/プロトコルは、トランスポートヘッダー情報を公開してネットワークから取得する恩恵を最適化することを選択できます[RFC8558]。トランスポート層の動作を分析するためのこの情報の値は、露光された情報がトランスポートプロトコルの観察された動作と一致するように検証され得る場合に強化されます。

The motivation to include actual transport header information and the implications of network devices using this information has to be considered when proposing such a method. [RFC8558] summarises this as:


   |  When signals from endpoints to the path are independent from the
   |  signals used by endpoints to manage the flow's state mechanics,
   |  they may be falsified by an endpoint without affecting the peer's
   |  understanding of the flow's state.  For encrypted flows, this
   |  divergence is not detectable by on-path devices.
6. Addition of Transport OAM Information to Network-Layer Headers
6. ネットワーク層ヘッダへのトランスポートOAM情報の追加

Even when the transport headers are encrypted, on-path devices can make measurements by utilising additional protocol headers carrying OAM information in an additional packet header. OAM information can be included with packets to perform functions, such as identification of transport protocols and flows, to aide understanding of network or transport performance or to support network operations or mitigate the effects of specific network segments.


Using network-layer approaches to reveal information has the potential that the same method (and hence same observation and analysis tools) can be consistently used by multiple transport protocols. This approach also could be applied to methods beyond OAM (see Section 5). There can also be less desirable implications from separating the operation of the transport protocol from the measurement framework.


6.1. Use of OAM within a Maintenance Domain
6.1. メンテナンスドメイン内のOAMの使用

OAM information can be restricted to a maintenance domain, typically owned and operated by a single entity. OAM information can be added at the ingress to the maintenance domain (e.g., an Ethernet protocol header with timestamps and sequence number information using a method such as 802.11ag or in-situ OAM [IOAM-DATA] or as a part of the encapsulation protocol). This additional header information is not delivered to the endpoints and is typically removed at the egress of the maintenance domain.

OAM情報は、通常、単一のエンティティによって所有および操作されたメンテナンスドメインに制限される可能性があります。OAM情報は、メンテナンスドメインへの入力(例えば、802.11AGやその場OAM [IOAMデータ]などのメソッドを使用したイーサネットプロトコルヘッダ、またはカプセル化プロトコルの一部としてのイーサネット番号情報を使用したイーサネットプロトコルヘッダー)を追加できます。)。この追加のヘッダ情報はエンドポイントに配信されず、通常はメンテナンスドメインの出力で削除されます。

Although some types of measurements are supported, this approach does not cover the entire range of measurements described in this document. In some cases, it can be difficult to position measurement tools at the appropriate segments/nodes, and there can be challenges in correlating the downstream/upstream information when in-band OAM data is inserted by an on-path device.


6.2. Use of OAM across Multiple Maintenance Domains
6.2. 複数のメンテナンスドメイン間でOAMを使用してください

OAM information can also be added at the network layer by the sender as an IPv6 extension header or an IPv4 option or in an encapsulation/ tunnel header that also includes an extension header or option. This information can be used across multiple network segments or between the transport endpoints.


One example is the IPv6 Performance and Diagnostic Metrics (PDM) destination option [RFC8250]. This allows a sender to optionally include a destination option that carries header fields that can be used to observe timestamps and packet sequence numbers. This information could be authenticated by a receiving transport endpoint when the information is added at the sender and visible at the receiving endpoint, although methods to do this have not currently been proposed. This needs to be explicitly enabled at the sender.


7. Conclusions
7. 結論

Header authentication and encryption and strong integrity checks are being incorporated into new transport protocols and have important benefits. The pace of the development of transports using the WebRTC data channel and the rapid deployment of the QUIC transport protocol can both be attributed to using the combination of UDP as a substrate while providing confidentiality and authentication of the encapsulated transport headers and payload.


This document has described some current practises, and the implications for some stakeholders, when transport-layer header encryption is used. It does not judge whether these practises are necessary or endorse the use of any specific practise. Rather, the intent is to highlight operational tools and practises to consider when designing and modifying transport protocols, so protocol designers can make informed choices about what transport header fields to encrypt and whether it might be beneficial to make an explicit choice to expose certain fields to devices on the network path. In making such a decision, it is important to balance:


User Privacy: The less transport header information that is exposed to the network, the lower the risk of leaking metadata that might have user privacy implications. Transports that chose to expose some header fields need to make a privacy assessment to understand the privacy cost versus benefit trade-off in making that information available. The design of the QUIC spin bit to the network is an example of such considered analysis.


Transport Ossification: Unencrypted transport header fields are likely to ossify rapidly, as network devices come to rely on their presence, making it difficult to change the transport in future. This argues that the choice to expose information to the network is made deliberately and with care, since it is essentially defining a stable interface between the transport and the network. Some protocols will want to make that interface as limited as possible; other protocols might find value in exposing certain information to signal to the network or in allowing the network to change certain header fields as signals to the transport. The visible wire image of a protocol should be explicitly designed.


Network Ossification: While encryption can reduce ossification of the transport protocol, it does not itself prevent ossification of the network service. People seeking to understand network traffic could still come to rely on pattern inferences and other heuristics or machine learning to derive measurement data and as the basis for network forwarding decisions [RFC8546]. This creates dependencies on the transport protocol or the patterns of traffic it can generate, resulting in ossification of the service.


Impact on Operational Practice: The network operations community has long relied on being able to understand Internet traffic patterns, both in aggregate and at the flow level, to support network management, traffic engineering, and troubleshooting. Operational practice has developed based on the information available from unencrypted transport headers. The IETF has supported this practice by developing operations and management specifications, interface specifications, and associated Best Current Practices. Widespread deployment of transport protocols that encrypt their information will impact network operations unless operators can develop alternative practises that work without access to the transport header.


Pace of Evolution: Removing obstacles to change can enable an increased pace of evolution. If a protocol changes its transport header format (wire image) or its transport behaviour, this can result in the currently deployed tools and methods becoming no longer relevant. Where this needs to be accompanied by development of appropriate operational support functions and procedures, it can incur a cost in new tooling to catch up with each change. Protocols that consistently expose observable data do not require such development but can suffer from ossification and need to consider if the exposed protocol metadata has privacy implications. There is no single deployment context; therefore, designers need to consider the diversity of operational networks (ISPs, enterprises, DDoS mitigation and firewall maintainers, etc.).


Supporting Common Specifications: Common, open, transport specifications can stimulate engagement by developers, users, researchers, and the broader community. Increased protocol diversity can be beneficial in meeting new requirements, but the ability to innovate without public scrutiny risks point solutions that optimise for specific cases and that can accidentally disrupt operations of/in different parts of the network. The social contract that maintains the stability of the Internet relies on accepting common transport specifications and on it being possible to detect violations. The existence of independent measurements, transparency, and public scrutiny of transport protocol behaviour helps the community to enforce the social norm that protocol implementations behave fairly and conform (at least mostly) to the specifications. It is important to find new ways of maintaining that community trust as increased use of transport header encryption limits visibility into transport behaviour (see also Section 5.3).


Impact on Benchmarking and Understanding Feature Interactions: An appropriate vantage point for observation, coupled with timing information about traffic flows, provides a valuable tool for benchmarking network devices, endpoint stacks, and/or configurations. This can help understand complex feature interactions. An inability to observe transport header information can make it harder to diagnose and explore interactions between features at different protocol layers, a side effect of not allowing a choice of vantage point from which this information is observed. New approaches might have to be developed.


Impact on Research and Development: Hiding transport header information can impede independent research into new mechanisms, measurements of behaviour, and development initiatives. Experience shows that transport protocols are complicated to design and complex to deploy and that individual mechanisms have to be evaluated while considering other mechanisms across a broad range of network topologies and with attention to the impact on traffic sharing the capacity. If increased use of transport header encryption results in reduced availability of open data, it could eliminate the independent checks to the standardisation process that have previously been in place from research and academic contributors (e.g., the role of the IRTF Internet Congestion Control Research Group (ICCRG) and research publications in reviewing new transport mechanisms and assessing the impact of their deployment).


Observable transport header information might be useful to various stakeholders. Other sets of stakeholders have incentives to limit what can be observed. This document does not make recommendations about what information ought to be exposed, to whom it ought to be observable, or how this will be achieved. There are also design choices about where observable fields are placed. For example, one location could be a part of the transport header outside of the encryption envelope; another alternative is to carry the information in a network-layer option or extension header. New transport protocol designs ought to explicitly identify any fields that are intended to be observed, consider if there are alternative ways of providing the information, and reflect on the implications of observable fields being used by on-path network devices and how this might impact user privacy and protocol evolution when these fields become ossified.


As [RFC7258] notes, "Making networks unmanageable to mitigate PM is not an acceptable outcome, but ignoring PM would go against the consensus documented here." Providing explicit information can help avoid traffic being inappropriately classified, impacting application performance. An appropriate balance will emerge over time as real instances of this tension are analysed [RFC7258]. This balance between information exposed and information hidden ought to be carefully considered when specifying new transport protocols.


8. Security Considerations
8. セキュリティに関する考慮事項

This document is about design and deployment considerations for transport protocols. Issues relating to security are discussed throughout this document.


Authentication, confidentiality protection, and integrity protection are identified as transport features by [RFC8095]. As currently deployed in the Internet, these features are generally provided by a protocol or layer on top of the transport protocol [RFC8922].


Confidentiality and strong integrity checks have properties that can also be incorporated into the design of a transport protocol or to modify an existing transport. Integrity checks can protect an endpoint from undetected modification of protocol fields by on-path network devices, whereas encryption and obfuscation or greasing can further prevent these headers being utilised by network devices [RFC8701]. Preventing observation of headers provides an opportunity for greater freedom to update the protocols and can ease experimentation with new techniques and their final deployment in endpoints. A protocol specification needs to weigh the costs of ossifying common headers versus the potential benefits of exposing specific information that could be observed along the network path to provide tools to manage new variants of protocols.

機密性と強力な整合性チェックには、トランスポートプロトコルの設計にも組み込まれたり、既存のトランスポートを変更したりすることができるプロパティがあります。Integrity Checksは、オンパスネットワークデバイスによってエンドポイントを検出しないようにすることができますが、暗号化や難読化や亀裂はさらにネットワークデバイスで使用されていることをさらに防ぐことができます[RFC8701]。ヘッダーの観察を防止すると、プロトコルを更新する自由が大きくなり、エンドポイントの新しい技術とその最終展開を容易にすることができます。プロトコル仕様は、プロトコルの新しい亜種を管理するためのツールを提供するためのツールを提供するためのネットワークパスに沿って観察され得る特定の情報を公開することの潜在的な利点の潜在的な利点の費用を重視する必要がある。

Header encryption can provide confidentiality of some or all of the transport header information. This prevents an on-path device from gaining knowledge of the header field. It therefore prevents mechanisms being built that directly rely on the information or seeks to infer semantics of an exposed header field. Reduced visibility into transport metadata can limit the ability to measure and characterise traffic and conversely can provide privacy benefits.


Extending the transport payload security context to also include the transport protocol header protects both types of information with the same key. A privacy concern would arise if this key was shared with a third party, e.g., providing access to transport header information to debug a performance issue would also result in exposing the transport payload data to the same third party. Such risks would be mitigated using a layered security design that provides one domain of protection and associated keys for the transport payload and encrypted transport headers and a separate domain of protection and associated keys for any observable transport header fields.

トランスポートペイロードセキュリティコンテキストを拡張すると、トランスポートプロトコルヘッダが同じキーで両方のタイプの情報を保護します。このキーが第三者と共有されている場合、Prafface Header情報へのアクセスを提供すると、パフォーマンスの問題が同じ第三者に転送ペイロードデータを公開することになるでしょう。そのようなリスクは、トランスポートペイロードおよび暗号化されたトランスポートヘッダおよび暗号化されたトランスポートヘッダに対する1つのドメインおよび関連する鍵のドメインを提供する階層化セキュリティ設計および任意の観察可能なトランスポートヘッダフィールドに対して個別の保護および関連するキーを提供する。

Exposed transport headers are sometimes utilised as a part of the information to detect anomalies in network traffic. As stated in [RFC7258], "While PM is an attack, other forms of monitoring that might fit the definition of PM can be beneficial and not part of any attack, e.g., network management functions monitor packets or flows and anti-spam mechanisms need to see mail message content." This can be used as the first line of defence to identify potential threats from DoS or malware and redirect suspect traffic to dedicated nodes responsible for DoS analysis, for malware detection, or to perform packet "scrubbing" (the normalisation of packets so that there are no ambiguities in interpretation by the ultimate destination of the packet). These techniques are currently used by some operators to also defend from distributed DoS attacks.


Exposed transport header fields can also form a part of the information used by the receiver of a transport protocol to protect the transport layer from data injection by an attacker. In evaluating this use of exposed header information, it is important to consider whether it introduces a significant DoS threat. For example, an attacker could construct a DoS attack by sending packets with a sequence number that falls within the currently accepted range of sequence numbers at the receiving endpoint. This would then introduce additional work at the receiving endpoint, even though the data in the attacking packet might not finally be delivered by the transport layer. This is sometimes known as a "shadowing attack". An attack can, for example, disrupt receiver processing, trigger loss and retransmission, or make a receiving endpoint perform unproductive decryption of packets that cannot be successfully decrypted (forcing a receiver to commit decryption resources, or to update and then restore protocol state).


One mitigation to off-path attacks is to deny knowledge of what header information is accepted by a receiver or obfuscate the accepted header information, e.g., setting a nonpredictable initial value for a sequence number during a protocol handshake, as in [RFC3550] and [RFC6056], or a port value that cannot be predicted (see Section 5.1 of [RFC8085]). A receiver could also require additional information to be used as a part of a validation check before accepting packets at the transport layer, e.g., utilising a part of the sequence number space that is encrypted or by verifying an encrypted token not visible to an attacker. This would also mitigate against on-path attacks. An additional processing cost can be incurred when decryption is attempted before a receiver discards an injected packet.


The existence of open transport protocol standards and a research and operations community with a history of independent observation and evaluation of performance data encourage fairness and conformance to those standards. This suggests careful consideration will be made over where, and when, measurement samples are collected. An appropriate balance between encrypting some or all of the transport header information needs to be considered. Open data and accessibility to tools that can help understand trends in application deployment, network traffic, and usage patterns can all contribute to understanding security challenges.


The security and privacy considerations in "A Framework for Large-Scale Measurement of Broadband Performance (LMAP)" [RFC7594] contain considerations for Active and Passive measurement techniques and supporting material on measurement context.


Addition of observable transport information to the path increases the information available to an observer and may, when this information can be linked to a node or user, reduce the privacy of the user. See the security considerations of [RFC8558].


9. IANA Considerations
9. IANAの考慮事項

This document has no IANA actions.


10. Informative References
10. 参考引用

[bufferbloat] Gettys, J. and K. Nichols, "Bufferbloat: Dark Buffers in the Internet", Communications of the ACM, Vol. 55, no. 1, pp. 57-65, DOI 10.1145/2063176.2063196, January 2012, <>.

[BufferBloat] GetTys、J.およびK.Nichols、 "BufferBloat:インターネット内の暗いバッファ"、ACMの通信、vol。55、いいえ。1、pp.57-65、DOI 10.1145 / 2063176.2063196、2012年1月、<>。

[DTLS] Rescorla, E., Tschofenig, H., and N. Modadugu, "The Datagram Transport Layer Security (DTLS) Protocol Version 1.3", Work in Progress, Internet-Draft, draft-ietf-tls-dtls13-43, 30 April 2021, <>.

[DTLS] Rescorla、E.、Tschofenig、H.、およびN. ModAdugu、「データグラムトランスポート層セキュリティ(DTLS)プロトコルバージョン1.3」、進行中の作業、インターネットドラフト、ドラフトIETF-TLS-DTLS13-43、2021年4月30日、<>。

[IOAM-DATA] Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields for In-situ OAM", Work in Progress, Internet-Draft, draft-ietf-ippm-ioam-data-12, 21 February 2021, <>.


[IPV6-ALT-MARK] Fioccola, G., Zhou, T., Cociglio, M., Qin, F., and R. Pang, "IPv6 Application of the Alternate Marking Method", Work in Progress, Internet-Draft, draft-ietf-6man-ipv6- alt-mark-06, 31 May 2021, <>.

[IPv6-ALT-MART] Fioccola、G.、Zhou、T.、Cociglio、M.、Qin、F、F.、R. Pang、「代替マーキング方法のIPv6適用」、進行中の作業、インターネットドラフト、draft-ietf-6man-IPv6- Alt-Mark-06,2021、<>。

[Latency] Briscoe, B., Brunstrom, A., Petlund, A., Hayes, D., Ros, D., Tsang, I., Gjessing, S., Fairhurst, G., Griwodz, C., and M. Welzl, "Reducing Internet Latency: A Survey of Techniques and Their Merits", IEEE Communications Surveys & Tutorials, vol. 18, no. 3, pp. 2149-2196, thirdquarter 2016, DOI 10.1109/COMST.2014.2375213, November 2014, <>.


[Measurement] Fairhurst, G., Kuehlewind, M., and D. Lopez, "Measurement-based Protocol Design", European Conference on Networks and Communications, Oulu, Finland., June 2017.

[測定] Fairhurst、G.、Kuehlewind、M.、D. Lopez、 "Measurement-Protocol Design"、ヨーロッパのネットワークおよびコミュニケーションに関するヨーロッパ会議、オウル、フィンランド。、2017年6月。

[PAM-RTT] Trammell, B. and M. Kuehlewind, "Revisiting the Privacy Implications of Two-Way Internet Latency Data", Passive and Active Measurement, March 2018.

[PAM-RTT] Trammell、B.およびM. Kuehlewind、「双方向インターネット待ち時間データのプライバシーの影響」、パッシブおよびアクティブな測定、2018年3月。

[PLUS-ABSTRACT-MECH] Trammell, B., "Abstract Mechanisms for a Cooperative Path Layer under Endpoint Control", Work in Progress, Internet-Draft, draft-trammell-plus-abstract-mech-00, 28 September 2016, <>.

[Plus-Abstract-Mech] Trammell、B、「エンドポイントコントロールの下での協調パス層の抽象メカニズム」、進捗状況、インターネットドラフト、ドラフト - Trammell-Plus-Abstract-Mech-00,2016、<>。

[QLOG] Marx, R., Niccolini, L., and M. Seemann, "Main logging schema for qlog", Work in Progress, Internet-Draft, draft-ietf-quic-qlog-main-schema-00, 10 June 2021, <>.

[Qlog] Marx、R.、Niccolini、L.、およびM. Seemann、「Qlogのメインロギングスキーマ」、進行中の作業、インターネットドラフト、ドラフト-IETF-Quic-Qlog-Main-Schema-00,10 6月2021、<>。

[Quic-Trace] "QUIC trace utilities", Commit 413c3a4, <>.

[QUIC-TRACE] "QUIC Trace Utilities"、COMMIT 413C3A4、<>。

[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, <>.

[RFC0791] Postel、J.、「インターネットプロトコル」、STD 5、RFC 791、DOI 10.17487 / RFC0791、1981年9月、<>。

[RFC2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and Its Use With IPsec", RFC 2410, DOI 10.17487/RFC2410, November 1998, <>.

[RFC2410] Glenn、R.およびS. Kent、「NULL暗号化アルゴリズムとIPsecとの使用」、RFC 2410、DOI 10.17487 / RFC2410、1998年11月、<>。

[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, December 1998, <>.

[RFC2474] Nichols、K.、Blake、S.、Baker、F.、およびD.黒、「IPv4およびIPv6ヘッダーのDSフィールドの定義」、RFC 2474、DOI 10.17487 / RFC2474、1998年12月、<>。

[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, <>.

[RFC2475] Blake、S.、Black、D.、Carlson、M.、Davies、E.、Wang、Z.、およびW.Weiss、「差別化サービスのためのアーキテクチャ」、RFC 2475、DOI 10.17487 / RFC2475、12月1998年、<>。

[RFC2507] Degermark, M., Nordgren, B., and S. Pink, "IP Header Compression", RFC 2507, DOI 10.17487/RFC2507, February 1999, <>.

[RFC2507] Degermark、M.、Nordgren、B.、およびS. Pink、 "IPヘッダー圧縮"、RFC 2507、DOI 10.17487 / RFC2507、1999年2月、<>。

[RFC2508] Casner, S. and V. Jacobson, "Compressing IP/UDP/RTP Headers for Low-Speed Serial Links", RFC 2508, DOI 10.17487/RFC2508, February 1999, <>.

[RFC2508] Casner、S.およびV.Jacobson、「低速シリアルリンク用のIP / UDP / RTPヘッダーの圧縮」、RFC 2508、DOI 10.17487 / RFC2508、1999年2月、<https://www.rfc-編集者。org / info / rfc2508>。

[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC 2914, DOI 10.17487/RFC2914, September 2000, <>.

[RFC2914] Floyd、S.、「輻輳制御原理」、BCP 41、RFC 2914、DOI 10.17487 / RFC2914、2000年9月、<>。

[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, DOI 10.17487/RFC3168, September 2001, <>.

[RFC3168] Ramakrishnan、K.、Floyd、S.、およびD. Black、「IPへの明示的輻輳通知(ECN)の追加」、RFC 3168、DOI 10.17487 / RFC3168、2001年9月、<https:// www。>。

[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002, <>.

[RFC3234] Carpenter、B.およびS. Brim、 "Midgleboxes:分類学と問題"、RFC 3234、DOI 10.17487 / RFC3234、2002年2月、<>。

[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, DOI 10.17487/RFC3261, June 2002, <>.

[RFC3261] Rosenberg、J.、Schulzrinne、H.、Camarillo、G.、Johnston、A.、Peterson、J.、Sparks、R.、Handley、M.、E. Schooler、「SIP:セッション開始プロトコル」、RFC 3261、DOI 10.17487 / RFC3261、2002年6月、<>。

[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI 10.17487/RFC3393, November 2002, <>.

[RFC3393] Demichelis、C.およびP. Chimento、IPパフォーマンスメトリック(IPPM)のIPパケット遅延バリエーションメトリック、RFC 3393、DOI 10.17487 / RFC3393、2002年11月、< info / rfc3393>。

[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, July 2003, <>.

[RFC3550] Schulzrinne、H.、Casner、S.、Frederick、R.、およびV. Jacobson、「RTP:リアルタイムアプリケーション用輸送プロトコル」、STD 64、RFC 3550、DOI 10.17487 / RFC3550、2003年7月、<>。

[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on Security Considerations", BCP 72, RFC 3552, DOI 10.17487/RFC3552, July 2003, <>.

[RFC3552] Rescorla、E.およびB.Korver、「セキュリティ上のRFCテキストを書くためのガイドライン」、BCP 72、RFC 3552、DOI 10.17487 / RFC3552、2003年7月、<情報/ RFC3552>。

[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC 3711, DOI 10.17487/RFC3711, March 2004, <>.

[RFC3711] Baugher、M.、McGrew、D.、Naslund、M.、Carrara、E.、K.Norrman、「安全なリアルタイムトランスポートプロトコル(SRTP)」、RFC 3711、DOI 10.17487 / RFC3711、3月2004年、<>。

[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, DOI 10.17487/RFC4302, December 2005, <>.

[RFC4302] Kent、S.、「IP認証ヘッダー」、RFC 4302、DOI 10.17487 / RFC4302、2005年12月、<>。

[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, DOI 10.17487/RFC4303, December 2005, <>.

[RFC4303]ケント、S。、「IPカプセル化セキュリティペイロード(ESP)」、RFC 4303、DOI 10.17487 / RFC4303、2005年12月、<>。

[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, "Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI 10.17487/RFC4585, July 2006, <>.

[RFC4585] OTT、J.、Wenger、S.、Sato、N.、Burmeister、C.、J.REY、「リアルタイムトランスポート制御プロトコルのための拡張RTPプロファイル(RTCP)ベースのフィードバック(RTP / AVPF)"、RFC 4585、DOI 10.17487 / RFC4585、2006年7月、<>。

[RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov, S., and J. Perser, "Packet Reordering Metrics", RFC 4737, DOI 10.17487/RFC4737, November 2006, <>.

[RFC4737]モートン、A。、Ciavattone、L.、Ramachandran、G.、Shalunov、S.、およびJ. Perser、「パケット並べ替えメトリクス」、RFC 4737、DOI 10.17487 / RFC4737、2006年11月、<>。

[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", RFC 4960, DOI 10.17487/RFC4960, September 2007, <>.

[RFC4960] Stewart、R.、Ed。、「ストリーム制御伝送プロトコル」、RFC 4960、DOI 10.17487 / RFC4960、2007年9月、<>。

[RFC5166] Floyd, S., Ed., "Metrics for the Evaluation of Congestion Control Mechanisms", RFC 5166, DOI 10.17487/RFC5166, March 2008, <>.

[RFC5166] Floyd、S.、ED。、「輻輳制御メカニズムの評価のための測定基準」、RFC 5166、DOI 10.17487 / RFC5166、2008年3月、<>。

[RFC5218] Thaler, D. and B. Aboba, "What Makes for a Successful Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008, <>.

[RFC5218] Thaler、D.およびB. Aboba、「正常なプロトコルのために何が成功させるのか」、RFC 5218、DOI 10.17487 / RFC5218、2008年7月、<>。

[RFC5236] Jayasumana, A., Piratla, N., Banka, T., Bare, A., and R. Whitner, "Improved Packet Reordering Metrics", RFC 5236, DOI 10.17487/RFC5236, June 2008, <>.

[RFC5236] Jayasumana、A.、Piratla、N.、Banka、T.、Bare、A.、R.Whitner、「改良されたパケット並べ替えメトリック」、RFC 5236、DOI 10.17487 / RFC5236、2008年6月、<>。

[RFC5426] Okmianski, A., "Transmission of Syslog Messages over UDP", RFC 5426, DOI 10.17487/RFC5426, March 2009, <>.

[RFC5426] Okmianski、A。、「UDP経由でのSyslogメッセージの送信」、RFC 5426、DOI 10.17487 / RFC5426、2009年3月、<>。

[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation Applicability Statement", RFC 5481, DOI 10.17487/RFC5481, March 2009, <>.

[RFC5481]モートン、A.およびB.Claise、「パケット遅延変動適用声明」、RFC 5481、DOI 10.17487 / RFC5481、2009年3月、<>。

[RFC5795] Sandlund, K., Pelletier, G., and L-E. Jonsson, "The RObust Header Compression (ROHC) Framework", RFC 5795, DOI 10.17487/RFC5795, March 2010, <>.

[RFC5795] Sandlund、K.、Pelletier、G、およびL-E。Jonsson、「堅牢なヘッダー圧縮(RoHC)フレームワーク」、RFC 5795、DOI 10.17487 / RFC5795、2010年3月、<>。

[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP Authentication Option", RFC 5925, DOI 10.17487/RFC5925, June 2010, <>.

[RFC5925] Touch、J.、Mankin、A.、R.ボニカ、「TCP認証オプション」、RFC 5925、DOI 10.17487 / RFC5925、2010年6月、< RFC5925>。

[RFC6056] Larsen, M. and F. Gont, "Recommendations for Transport-Protocol Port Randomization", BCP 156, RFC 6056, DOI 10.17487/RFC6056, January 2011, <>.

[RFC6056] Larsen、M.およびF.は、「トランスポートプロトコルポートランダム化のための推奨事項」、BCP 156、RFC 6056、DOI 10.17487 / RFC6056、2011年1月、< RFC6056>。

[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and P. Roberts, "Issues with IP Address Sharing", RFC 6269, DOI 10.17487/RFC6269, June 2011, <>.

[RFC6269]フォード、M、ED。、Boucadair、M.、Durand、A.、Levis、P.、およびP. Roberts、RFC 6269、DOI 10.17487 / RFC6269、2011年6月、<>。

[RFC6294] Hu, Q. and B. Carpenter, "Survey of Proposed Use Cases for the IPv6 Flow Label", RFC 6294, DOI 10.17487/RFC6294, June 2011, <>.

[RFC6294] HU、Q.およびB. Carpenter、RFC 6294、DOI 10.17487 / RFC6294、2011年6月、< RFC6294>。

[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012, <>.

[RFC6347] RESCORLA、E.およびN. MODADUGU、「データグラムトランスポートレイヤセキュリティバージョン1.2」、RFC 6347、DOI 10.17487 / RFC6347、2012年1月、<>。

[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, "IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/RFC6437, November 2011, <>.

[RFC6437] Amante、S.、Carpenter、B.、Jiang、S.、およびJ.Rajahalme、「IPv6フローラベル仕様」、RFC 6437、DOI 10.17487 / RFC6437、2011年11月、<>。

[RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label for Equal Cost Multipath Routing and Link Aggregation in Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011, <>.

[RFC6438] Carpenter、B.およびS. Amante、「トンネルの同等のコストマルチパスルーティングのためのIPv6フローラベルの使用」、RFC 6438、DOI 10.17487 / RFC6438、2011年11月、<>

[RFC6846] Pelletier, G., Sandlund, K., Jonsson, L-E., and M. West, "RObust Header Compression (ROHC): A Profile for TCP/IP (ROHC-TCP)", RFC 6846, DOI 10.17487/RFC6846, January 2013, <>.

[RFC6846]ペレチェ、G.、Sandlund、K.、Jonsson、Le。、およびM. West、 "Robust Header Compression(RoHC):TCP / IP(RoHC-TCP)"、RFC 6846、DOI 10.17487 /rfc6846、2013年1月、<>。

[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., Morris, J., Hansen, M., and R. Smith, "Privacy Considerations for Internet Protocols", RFC 6973, DOI 10.17487/RFC6973, July 2013, <>.

[RFC6973]クーパー、A.、Tschofenig、H.、Aboba、B.、Peterson、J.、Morris、J.、Hansen、M.、R. Smith、「インターネットプロトコルのプライバシーに関する考察」、RFC 6973、DOI2017487 / RFC6973、2013年7月、<>。

[RFC7098] Carpenter, B., Jiang, S., and W. Tarreau, "Using the IPv6 Flow Label for Load Balancing in Server Farms", RFC 7098, DOI 10.17487/RFC7098, January 2014, <>.

[RFC7098] Carpenter、B.、Jiang、S.およびW. Tarreau、2014年1月、2014年1月、<https:// www。>。

[RFC7126] Gont, F., Atkinson, R., and C. Pignataro, "Recommendations on Filtering of IPv4 Packets Containing IPv4 Options", BCP 186, RFC 7126, DOI 10.17487/RFC7126, February 2014, <>.

[RFC7126] Gont、F.、Atkinson、R.およびC. Pignataro、「IPv4オプションを含むIPv4パケットのフィルタリングに関する推奨事項」、BCP 186、RFC 7126、DOI 10.17487 / RFC7126、2014年2月、<https:// / info / rfc7126>。

[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May 2014, <>.

[RFC7258] Farrell、S.およびH.Tschofenig、「Pervasive Monitoringは攻撃」、BCP 188、RFC 7258、DOI 10.17487 / RFC7258、2014年5月、<>。

[RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, <>.

[RFC7413] Cheng、Y.、Chu、J.、Radhakrishnan、S.、A. Jain、 "TCP Fast Open"、RFC 7413、DOI 10.17487 / RFC7413、2014年12月、<https:///www.rfc-編集者.ORG / INFO / RFC7413>。

[RFC7414] Duke, M., Braden, R., Eddy, W., Blanton, E., and A. Zimmermann, "A Roadmap for Transmission Control Protocol (TCP) Specification Documents", RFC 7414, DOI 10.17487/RFC7414, February 2015, <>.

[RFC7414] Duke、M.、Braden、R.、Eddy、W.、Blanton、E.、A.Zimmermann、「トランスミッション制御プロトコル(TCP)仕様書のロードマップ」、RFC 7414、DOI 10.17487 / RFC7414、2015年2月、<>。

[RFC7567] Baker, F., Ed. and G. Fairhurst, Ed., "IETF Recommendations Regarding Active Queue Management", BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015, <>.

[RFC7567] Baker、F.、ED。G. FairHurst、Ed。、「アクティブキュー管理に関するIETF勧告」、BCP 197、RFC 7567、DOI 10.17487 / RFC7567、2015年7月、<>。

[RFC7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T., Aitken, P., and A. Akhter, "A Framework for Large-Scale Measurement of Broadband Performance (LMAP)", RFC 7594, DOI 10.17487/RFC7594, September 2015, <>.

[RFC7594]イヤードリー、P.、モートン、A。、Bagnulo、M.、Burbridge、T.、Aitken、P.、A. AKHTER、「ブロードバンド性能の大規模測定のためのフレームワーク(LMAP)」、RFC7594、DOI 10.17487 / RFC7594、2015年9月、<>。

[RFC7605] Touch, J., "Recommendations on Using Assigned Transport Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605, August 2015, <>.

[RFC7605] Touch、J.、「割り当てられたトランスポートポート番号を使用する推奨事項」、BCP 165、RFC 7605、DOI 10.17487 / RFC7605、2015年8月、<>。

[RFC7624] Barnes, R., Schneier, B., Jennings, C., Hardie, T., Trammell, B., Huitema, C., and D. Borkmann, "Confidentiality in the Face of Pervasive Surveillance: A Threat Model and Problem Statement", RFC 7624, DOI 10.17487/RFC7624, August 2015, <>.

[RFC7624] Barnes、R.、Schneier、B、Jennings、C.、Hardie、T.、Trammell、B.、Huitema、C.、D.Borkmann、「浸透監視の顔の機密性:脅威モデル2015年8月、<>を参照してください」、RFC 7624、DOI 10.17487 / RFC7624、DOI 10.17487 / RFC7624。

[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, May 2016, <>.

[RFC7799]モートン、A。、「能動的および受動的な測定基準および方法(インス間のハイブリッドタイプおよびメソッド)、RFC 7799、DOI 10.17487 / RFC7799、2016年5月、< RFC7799>。

[RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu, "Observations on the Dropping of Packets with IPv6 Extension Headers in the Real World", RFC 7872, DOI 10.17487/RFC7872, June 2016, <>.

[RFC7872]ゴント、F、Linkova、J.、Chown、T.、およびW. Liu、RFC 7872、DOI 10.17487 / RFC7872、2016年6月<>。

[RFC7928] Kuhn, N., Ed., Natarajan, P., Ed., Khademi, N., Ed., and D. Ros, "Characterization Guidelines for Active Queue Management (AQM)", RFC 7928, DOI 10.17487/RFC7928, July 2016, <>.

[RFC7928] Kuhn、N.、Ed。、Natarajan、P.、Ed。、Khademi、N.、Ed。、およびD. ROS、「アクティブキュー管理のための特性評価ガイドライン(AQM)」、RFC 7928、DOI 10.17487 /RFC7928、2016年7月、<>。

[RFC7983] Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme Updates for Secure Real-time Transport Protocol (SRTP) Extension for Datagram Transport Layer Security (DTLS)", RFC 7983, DOI 10.17487/RFC7983, September 2016, <>.

[RFC7983] Petit-Huguenin、M.およびG.Salgueiro、データグラムトランスポート層セキュリティ(DTLS)拡張(DTLS)拡張(DTLS)拡張(DTLS))、RFC 7983、DOI 10.17487 / RFC7983、2016年9月、<>。

[RFC8033] Pan, R., Natarajan, P., Baker, F., and G. White, "Proportional Integral Controller Enhanced (PIE): A Lightweight Control Scheme to Address the Bufferbloat Problem", RFC 8033, DOI 10.17487/RFC8033, February 2017, <>.

[RFC8033] Pan、R.、Natarajan、P.、Baker、F.、およびG. White、 "比例積分コントローラ拡張(パイ):バッファブロートの問題に対処するための軽量制御方式"、RFC 8033、DOI 10.17487 / RFC8033、2017年2月、<>。

[RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017, <>.

[RFC8084] FairHurst、G.、「ネットワークトランスポートサーキットブレーカ」、BCP 208、RFC 8084、DOI 10.17487 / RFC8084、2017年3月、<>。

[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, March 2017, <>.

[RFC8085] eggert、L.、Fairhurst、G.、およびG.Shepherd、 "UDP使用ガイドライン"、BCP 145、RFC 8085、DOI 10.17487 / RFC8085、2017年3月、< info / rfc8085>。

[RFC8086] Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086, March 2017, <>.

[RFC8086] Yong、L.、Ed。、Crabbe、E.、Xu、X.、およびT.Herbert、「Gre-In-UDPカプセル化」、RFC 8086、DOI 10.17487 / RFC8086、2017年3月、<>。

[RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using Explicit Congestion Notification (ECN)", RFC 8087, DOI 10.17487/RFC8087, March 2017, <>.

[RFC8087] FairHurst、G.およびM. Welzl、「明示的輻輳通知(ECN)を使用する利点」、RFC 8087、DOI 10.17487 / RFC8087、2017年3月、< RFC8087>。

[RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind, Ed., "Services Provided by IETF Transport Protocols and Congestion Control Mechanisms", RFC 8095, DOI 10.17487/RFC8095, March 2017, <>.

[RFC8095] Fairhurst、G.、Ed。、Trammell、B.、Ed。、およびM.Kuehlewind、ED。、「IETFトランスポートプロトコルと輻輳制御メカニズムによるサービス」、RFC 8095、DOI 10.17487 / RFC8095、2017年3月<>。

[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, <>.

[RFC8200] The'th、S.およびR.hinden、「インターネットプロトコル、バージョン6(IPv6)仕様」、STD 86、RFC 8200、DOI 10.17487 / RFC8200、2017年7月、< info / rfc8200>。

[RFC8250] Elkins, N., Hamilton, R., and M. Ackermann, "IPv6 Performance and Diagnostic Metrics (PDM) Destination Option", RFC 8250, DOI 10.17487/RFC8250, September 2017, <>.

[RFC8250] Elkins、N.、Hamilton、R.、およびM.Ackermann、「IPv6性能と診断メトリクス(PDM)宛先オプション」、RFC 8250、DOI 10.17487 / RFC8250、2017年9月、<>。

[RFC8289] Nichols, K., Jacobson, V., McGregor, A., Ed., and J. Iyengar, Ed., "Controlled Delay Active Queue Management", RFC 8289, DOI 10.17487/RFC8289, January 2018, <>.

[RFC8289] Nichols、K.、Jacobson、V.、McGregor、A.、ED。、およびJ.Iyengar、ED。、「管理遅延アクティブキュー管理」、RFC 8289、DOI 10.17487 / RFC8289、2018年1月、<HTTPS///>。

[RFC8290] Hoeiland-Joergensen, T., McKenney, P., Taht, D., Gettys, J., and E. Dumazet, "The Flow Queue CoDel Packet Scheduler and Active Queue Management Algorithm", RFC 8290, DOI 10.17487/RFC8290, January 2018, <>.

[RFC8290] Hoeiland-Joergensen、T.、McKenney、P.、Taht、D.、GetTys、J.、E.Dumazet、「フローキューコーデルパケットスケジューラとアクティブキュー管理アルゴリズム」、RFC 8290、DOI 10.17487 /RFC8290、2018年1月、<>。

[RFC8404] Moriarty, K., Ed. and A. Morton, Ed., "Effects of Pervasive Encryption on Operators", RFC 8404, DOI 10.17487/RFC8404, July 2018, <>.

[RFC8404] MoriAlty、K。、ED。A. Morton、Ed。、「オペレータ上の周辺暗号化の影響」、RFC 8404、DOI 10.17487 / RFC8404、2018年7月、<>。

[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, <>.

[RFC8446] RESCORLA、E.、「トランスポート層セキュリティ(TLS)プロトコルバージョン1.3」、RFC 8446、DOI 10.17487 / RFC8446、2018年8月、<>。

[RFC8462] Rooney, N. and S. Dawkins, Ed., "Report from the IAB Workshop on Managing Radio Networks in an Encrypted World (MaRNEW)", RFC 8462, DOI 10.17487/RFC8462, October 2018, <>.

[RFC8462] Rooney、N.およびS.Dawkins、「暗号化された世界のラジオネットワークの管理上のIABワークショップからの報告」、RFC 8462、DOI 10.17487 / RFC8462、2018年10月、<>。

[RFC8517] Dolson, D., Ed., Snellman, J., Boucadair, M., Ed., and C. Jacquenet, "An Inventory of Transport-Centric Functions Provided by Middleboxes: An Operator Perspective", RFC 8517, DOI 10.17487/RFC8517, February 2019, <>.

[RFC8517] Dolson、D.、ED。、Snellman、J.、Boucadair、M.、Ed。、およびC.Jacquenet、「ミドルボックスによって提供されるトランスポート中心関数のインベントリ:オペレータの展望」、RFC 8517、DOI10.17487 / RFC8517、2019年2月、<>。

[RFC8546] Trammell, B. and M. Kuehlewind, "The Wire Image of a Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April 2019, <>.

[RFC8546] Trammell、B.およびM. Kuehlewind、「ネットワークプロトコルのワイヤ画像」、RFC 8546、DOI 10.17487 / RFC8546、2019年4月、<>。

[RFC8548] Bittau, A., Giffin, D., Handley, M., Mazieres, D., Slack, Q., and E. Smith, "Cryptographic Protection of TCP Streams (tcpcrypt)", RFC 8548, DOI 10.17487/RFC8548, May 2019, <>.

[RFC8548] Bittau、A.、Giffin、D.、Handley、M.、Mazieres、D.、Slack、Q.、およびE.Smith、「TCPストリームの暗号保護(TCPCRYPT)」、RFC 8548、DOI 10.17487 /RFC8548、2019年5月、<>。

[RFC8558] Hardie, T., Ed., "Transport Protocol Path Signals", RFC 8558, DOI 10.17487/RFC8558, April 2019, <>.

[RFC8558] Hardie、T.、ED。、「トランスポートプロトコルパス信号」、RFC 8558、DOI 10.17487 / RFC8558、2019年4月、<>。

[RFC8684] Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C. Paasch, "TCP Extensions for Multipath Operation with Multiple Addresses", RFC 8684, DOI 10.17487/RFC8684, March 2020, <>.

[RFC8684]フォード、A.、RaiCyu、C.、Handley、M.、Bonaventure、O.、およびC. PaaSch、RFC 8684、DOI 10.17487 / RFC8684、2020年3月、<>。

[RFC8701] Benjamin, D., "Applying Generate Random Extensions And Sustain Extensibility (GREASE) to TLS Extensibility", RFC 8701, DOI 10.17487/RFC8701, January 2020, <>.

[RFC8701] Benjamin、D.、「ランダム拡張の施用と維持拡張性(グリース)への伸縮性(Grease)extensibility」、RFC 8701、DOI 10.17487 / RFC8701、2020年1月、<>。

[RFC8724] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC. Zúñiga, "SCHC: Generic Framework for Static Context Header Compression and Fragmentation", RFC 8724, DOI 10.17487/RFC8724, April 2020, <>.

[RFC8724]ミナブロ、A.、Toutain、L.、Gomez、C、Barthel、D.、およびJC。Zúñiga、 "Schc:静的コンテキストヘッダ圧縮および断片化のための一般的なフレームワーク"、RFC 8724、DOI 10.17487 / RFC8724、2020年4月、<>。

[RFC8837] Jones, P., Dhesikan, S., Jennings, C., and D. Druta, "Differentiated Services Code Point (DSCP) Packet Markings for WebRTC QoS", RFC 8837, DOI 10.17487/RFC8837, January 2021, <>.

[RFC8837] Jones、P.、Ashesikan、S.、Jennings、C、およびD. Druta、「微分サービスコードポイント(DSCP)パケットマーキング」、RFC 8837、DOI 10.17487 / RFC8837、2021年1月、<>。

[RFC8866] Begen, A., Kyzivat, P., Perkins, C., and M. Handley, "SDP: Session Description Protocol", RFC 8866, DOI 10.17487/RFC8866, January 2021, <>.

[RFC8866] Begen、A.、Kyzivat、P.、Perkins、C、およびM.ハンドリー、「SDP:セッション記述プロトコル」、RFC 8866、DOI 10.17487 / RFC8866、2021年1月、<>。

[RFC8922] Enghardt, T., Pauly, T., Perkins, C., Rose, K., and C. Wood, "A Survey of the Interaction between Security Protocols and Transport Services", RFC 8922, DOI 10.17487/RFC8922, October 2020, <>.

[RFC8922] enghardt、T.、Pauly、T.、Perkins、C、Rose、K.、およびC.木材、「セキュリティプロトコルとトランスポートサービス間の相互作用の調査」、RFC 8922、DOI 10.17487 / RFC8922、2020年10月、<>。

[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, <>.

[RFC9000] Iyengar、J.、ED。そして、「Q. Thomson」、「QUIC:UDPベースの多重化および安全な輸送」、RFC 9000、DOI 10.17487 / RFC9000、<>。



The authors would like to thank Mohamed Boucadair, Spencer Dawkins, Tom Herbert, Jana Iyengar, Mirja Kühlewind, Kyle Rose, Kathleen Moriarty, Al Morton, Chris Seal, Joe Touch, Brian Trammell, Chris Wood, Thomas Fossati, Mohamed Boucadair, Martin Thomson, David Black, Martin Duke, Joel Halpern, and members of TSVWG for their comments and feedback.

著者らは、Mohamed Boucadair、Spencer Dawkins、Tom Herbert、Jana Iyengar、MirjaKühlewind、Kyle Rose、Kyle Rose、Kathleen Moriarty、Al Morton、Chris Seal、Joe Touch、Brian Tramsell、Thomas Fossati、Marined Boucadair、Martin Thomson、David Black、Martin Duke、Joel Halpern、そして彼らのコメントとフィードバックのためのTSVWGのメンバー。

This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 688421 and the EU Stand ICT Call 4. The opinions expressed and arguments employed reflect only the authors' views. The European Commission is not responsible for any use that might be made of that information.


This work has received funding from the UK Engineering and Physical Sciences Research Council under grant EP/R04144X/1.


Authors' Addresses


Godred Fairhurst University of Aberdeen Department of Engineering Fraser Noble Building Aberdeen, Scotland AB24 3UE United Kingdom

Aberdeen of Aberdeen of Aberdeen大学エンジニアリングFraser Noble Building Aberdeen、スコットランドAB24 3UEイギリス


Colin Perkins University of Glasgow School of Computing Science Glasgow, Scotland G12 8QQ United Kingdom

Colin Perkins Glasgow大学コンピューティングサイエンス学校glasgow、スコットランドG12 8QQイギリス