INTERNET-DRAFT Donald Eastlake Intended status: Proposed Standard Futurewei Technologies Bob Briscoe Independent Andrew Malis
Futurewei TechnologiesIndependent Expires: June 31, 2020January 1, 2021 July 2, 2020 Explicit Congestion Notification (ECN) and Congestion Feedback Using the Network Service Header (NSH) <draft-ietf-sfc-nsh-ecn-support-02.txt><draft-ietf-sfc-nsh-ecn-support-03.txt> Abstract Explicit congestion notification (ECN) allows a forwarding element to notify downstream devices of the onset of congestion without having to drop packets. Coupled with a means to feed back information about congestion to upstream nodes, this can improve network efficiency through better congestion control, frequently without packet drops. This document specifies ECN and congestion feedback support within a Service Function Chaining (SFC) domain through use of the Network Service Header (NSH, RFC 8300) and IP Flow Information Export (IPFIX, draft-ietf-tsvwg-tunnel-congestion-feedback). Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Distribution of this document is unlimited. Comments should be sent to the SFC Working Group mailing list <firstname.lastname@example.org> or to the authors. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. INTERNET-DRAFT NSH ECN & Congestion Feedback Table of Contents 1. Introduction............................................3 1.1 NSH Background.........................................3 1.2 ECN Background.........................................5 1.3 Tunnel Congestion Feedback Background..................5 1.4 Conventions Used in This Document......................7 2. The NSH ECN Field.......................................8 3. ECN Support in the NSH.................................10 3.1 At The Ingress........................................11 3.2 At Transit Nodes......................................12 3.2.1 At NSH Transit Nodes................................12 3.2.2 At an SF/Proxy......................................13 3.2.3 At Other Forwarding Nodes...........................13 3.3 At Exit/Egress........................................13 3.4 Conservation of Packets...............................14 4. Tunnel Congestion Feedback Support.....................15 5. IANA Considerations....................................16 6. Security Considerations................................17 7. Acknowledgements.......................................17 Normative References......................................18 Informative References....................................19 Authors' Addresses........................................20 INTERNET-DRAFT NSH ECN & Congestion Feedback 1. Introduction Explicit congestion notification (ECN [RFC3168]) allows a forwarding element to notify downstream devices of the onset of congestion without having to drop packets. Coupled with a means to feed back information about congestion to upstream nodes, this can improve network efficiency through better congestion control, frequently without packet drops. This document specifies ECN and congestion feedback support within a Service Function Chaining (SFC [RFC7665]) domain through use of the Network Service Header (NSH [RFC8300]) and IP Flow Information Export (IPFIX [TunnelCongFeedback]). It requires that all ingress and egress nodes of the SFC domain implement ECN. While congestion management will be the most effective if all interior nodes of the SFC domain implement ECN, some benefit is obtained even if some interior nodes do not implement ECN. In particular, congestion at any bottleneck where ECN marking is not implemented will be unmanaged. The subsections below in this issection provide background information on NSH, ECN, congestion feedback, and terminology used in this document. 1.1 NSH Background The Service Function Chaining (SFC [RFC7665]) architecture calls for the encapsulation of traffic within a service function chaining domain with a Network Service Header (NSH [RFC8300]) added by the "Classifier" (ingress node) on entry to the domain and the NSH being removed on exit from the domain at the egress node. The NSH is used to control the path of a packet in an SFC domain. The NSH is a natural place, in a domain where traffic is NSH encapsulated, to note congestion, avoiding possible confusion due, for example, to changes in the outer transport header in different parts of the domain. INTERNET-DRAFT NSH ECN & Congestion Feedback | v +----------+ . .|Classifier|. . . . . . . . . . . . . . . +----------+ . . | +----+ . . | --+ SF | Service . . | / +----+ Function . . v --- Chaining . . +-----+/ +----+ domain . . | SFF |--------+ SF | . . +-----+\ +----+ . . | --- . . | \ +----+ . . | --+ SF | . . v +----+ . . +-----+ +----+ . . | SFF |-----------------+ SF | . . +-----+ +----+ . . | +----+ . . | --+ SF | . . | / +----+ . . v --- . . +-----+/ +----+ . . | SFF |--------+ SF | . . +-----+\ +----+ . . | --- . . | \ +----+ . . | --+ SF | . . v +----+ . . +------+ . . . .| Exit |. . . . . . . . . . . . . . . +------+ | v Figure 1. Example SFC Path Forwarding Nodes Figure 1 shows an SFC domain for the purpose of illustrating the use of the NSH. Traffic passes through a sequence of Service Function Forwarders (SFFs) each of which sends the traffic to one or more Service Functions (SFs). Each SF performs some operation on the traffic, for example firewall or Network Address Translation (NAT), and then returns it to the SFF from which it was received. Logically, during the transit of each SFF, the outer transport header that got the packet to the SFF is stripped, the SFF decides on the next forwarding step, either adding a transport header or, if the SFF is the exit/egress, removing the NSH header. The transport headers INTERNET-DRAFT NSH ECN & Congestion Feedback added may be different in different regions of the SFC domain. For example, IP could be used for some SFF-to-SFF communication and MPLS used for other such communication. 1.2 ECN Background Explicit congestion notification (ECN [RFC3168]) allows a forwarding element (such as a router or a Service Function Forwarder (SFF) or Service Function (SF)) to notify downstream devices of the onset of congestion without having to drop packets. This can be used as an element in active queue management (AQM) [RFC7567] to improve network efficiency through better traffic control without packet drops. The forwarding element can explicitly mark some packets in an ECN field instead of dropping the packet. For example, a two-bit field is available for ECN marking in IP headers [RFC3168]. 1.3 Tunnel Congestion Feedback Background Tunnel Congestion Feedback [TunnelCongFeedback] is a building block for various congestion mitigation methods. It supports feedback of congestion information from an egress node to an ingress node. Examples of actions that can be taken by an ingress node when it has knowledge of downstream congestion include those listed below. Details of implementing these traffic control methods, beyond those given here, are outside the scope of this document. Any action by the ingress to reduce congestion needs to allow sufficient time for the end-to-end congestion control loop to respond first, for instance by the ingress taking a smoothed average of the level of congestion signalled by feedback from the tunnel egress. (1) Traffic throttling (policing), where the downstream traffic flowing out of the ingress node is limited to reduce or eliminate congestion. (2) Upstream congestion feedback, where the ingress node sends messages upstream to or towards the ultimate traffic source, a function that can throttle traffic generation/transmission. (3) Traffic re-direction, where the ingress node configures the NSH of some future traffic so that it avoids congested paths. Great care must be taken with this option to avoid (a) significant re-orderingre- ordering of traffic in flows that it is desirable to keep in order and (b) oscillation/instability in traffic paths due to alternate congestion of previously idle paths and the idling of previously congested paths. For example, it is preferable to classifyINTERNET-DRAFT NSH ECN & Congestion Feedback classify traffic into flows of a sufficiently coarse granularity that the flows are long lived and then use a stable path per flow, then sendsending only newly appearing flows on apparently uncongested paths. Figure 2 shows an example path from an origin sender to a final receiver passing through an example chain of service functions between the ingress and egress of an SFC domain. The path is also likely to pass through other network nodes outside the SFC domain (not shown). The figure shows typical congestion feedback that would be expected from the final receiver to the origin sender, which controls the load the origin sender applies to all elements on the path. The figure also shows the congestion feedback from the egress to the ingress of the SFC domain that is described in this document, to control or balance load within the SFC domain. .:= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = :. _||_ End-to-End Congestion Feedback || \ / || \/ || __ Inner Transport Header and Payload __ | | - -->- - - - - - - - - - - - - - ->- - - - - -- - - - - - - -->- | | | | | | | | .:= = = = = = = = = = = = = = = = = = = = = =:. | | | | _||_ Tunnel Congestion Feedback || | | | | \ / || | | | | \/ || | | | | __ NSH __ | | | | | |-------------------------->--------------| | | | | |. . . | | ___ ___ ___ | |. . .| | | | | | OT1 | | OT4 | | . . . | | OTn | | | | | | | |-->--|SFF|--->---|SFF| |SFF|-->--| | | | |__| |__| |___| |___| |___| |__| |__| origin SFC | ^ | ^ SFC final sender domain OT2| |OT3 OT6| |OT7 domain rcvr ingress v | v | egress +---+ +---+ |SF | |SF | +---+ +---+ Figure 2: Congestion Feedback across an SFC Domain SFC Domain congestion feedback in Figure 2 is shown within the context of an end-to-end congestion feedback loop. Also shown is the encapsulated layering of NSH headers within a series of outer transport headers (OT1, OT2, ... OTn). INTERNET-DRAFT NSH ECN & Congestion Feedback 1.4 Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. Acronyms: AQM - Active Queue Management [RFC7567] CE - Congestion Experienced [RFC3168] downstream - The direction from ingress to egress ECN - Explicit Congestion Notification [RFC3168] ECT - ECN Capable Transport [RFC3168] IPFIX - IP Flow Information Export [RFC7011] Not-ECT - Not ECN-Capable Transport [RFC3168] NSH - Network Service Header [RFC8300] SF - Service Function [RFC7665] SFC - Service Function Chaining [RFC7665] SFF - Service Function Forwarder [RFC7665] - A type of node that forwards based on the NSH. TLV - Type Length Value upstream - The direction from egress to ingress INTERNET-DRAFT NSH ECN & Congestion Feedback 2. The NSH ECN Field The NSH header is used to encapsulate and control the subsequent path of traffic (see Section 2 of [RFC8300]). The NSH also provides for metadata inclusion, as shown in Figure 3. +-----------------------------------+ | Transport Encapsulation | +-----------------------------------+ | Network Service Header (NSH) | | +------------------------------+ | | | Base Header | | | +------------------------------+ | | | Service Path Header | | | +------------------------------+ | | | Metadata (Context Header(s)) | | | +------------------------------+ | +-----------------------------------+ | Original Packet / Frame | +-----------------------------------+ Figure 3. Data Encapsulation with the NSH Two currently unused bits (indicated by "U") in the NSH Base Header (Section 2.2 of [RFC8300]) are allocated for ECN as shown in Figure 4. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ^ ^ | | +-------+ |NSH ECN| | field | +-------+ Figure 4: NSH Base Header Note to RFC Editor: The above figure should be adjusted based on the bits assigned by IANA (see Section 5) and this note deleted. Table 1 shows the meaning of the code points in the NSH ECN field. These have the same meaning as the ECN field code points in the IPv4 or IPv6 header as defined in [RFC3168]. INTERNET-DRAFT NSH ECN & Congestion Feedback Binary Name Meaning ------ ------- -------------------------------- 00 Not-ECT Not ECN-Capable Transport 01 ECT(1) ECN-Capable Transport 10 ECT(0) ECN-Capable Transport 11 CE Congestion Experienced Table 1. ECN Field Code Points INTERNET-DRAFT NSH ECN & Congestion Feedback 3. ECN Support in the NSH This section describes the required behavior to support ECN using the NSH. There are two aspects to ECN support: 1. ECN propagation during encapsulation or decapsulation 2. ECN marking during congestion at bottlenecks. While this section covers all combinations of ECN-aware and not ECN- aware, it is expected that in most cases the NSH domain will be uniform so that, if this document is applicable, all SFFs will support ECN; however, some legacy SFs might not support ECN. ECN Propagation: The specification of ECN tunneling [RFC6040] explains that an ingress must not propagate ECN support into an encapsulating header unless the egress supports correct onward propagation of the ECN field during decapsulation. We define Compliant ECN Decapsulation here as decapsulation compliant with either [RFC6040] or an earlier compatible equivalent ([RFC4301], or the full functionality mode of [RFC3168]). The procedures in Section 3.2.1 ensure that each ingress of the large number of possible transport links within the SFC domain does not propagate ECN support into the encapsulating outer transport header unless the corresponding egress of that link supports Compliant ECN Decapsulation. Section 3.3 requires that all the egress nodes of the SFC domain support Compliant ECN Decapsulation in conjunction with tunnel congestion feedback, otherwise the scheme in this document will not work. ECN Marking: At transit nodes the marking behavior specified in Section 3.2.1 is recommended and if not implemented at such transit nodes, there may be unmanaged congestion. Detection of congestion will be most effective if ECN marking is supported by all potential bottlenecks inside the domain in which NSH is being used to route traffic as well as at the ingress and egress. Nodes that do not support ECN marking, or that support AQM but not ECN, will naturally use drop to relieve congestion. The gap in the end-to-end packet sequence will be detected as congestion by the final receiving endpoint, but not by the NSH egress (see Figure 2). INTERNET-DRAFT NSH ECN & Congestion Feedback 3.1 At The Ingress When the ingress/Classifier encapsulates an incoming IP packet with an NSH, it MUST set the NSH ECN field using the "Normal mode" specified in [RFC6040] (i.e., copied from the incoming IP header). Then, if the resulting NSH ECN field is Not-ECT, the ingress SHOULD set it to ECT(0). This indicates that, even though the end-to-end transport is not ECN-capable, the egress and ingress of the SFC domain are acting as an ECN-capable transport. This approach will inherently support all known variatnsvariants of ECN, including the experimental L4S capability [RFC8311],[RFC8311] [ecnL4S]. Packets arriving at the ingress might not use IP. If the protocol of arriving packets supports an ECN field similar to IP, the procedures for IP packets can be used. If arriving packets do not support an ECN field similar to IP, they MUST be treated as if they are Not-ECT IP packets. Then, as the NSH encapsulated packet is further encapsulated with a transport header, if ECN marking is available for that transport (as it is for IP [RFC3168] and MPLS [RFC5129]), the ECN field of the transport header MUST be set using the "Normal mode" specified in [RFC6040] (i.e., copied from the NSH ECN field). A summary of these normative steps is given in Table 2. +-----------------+---------------+ | Incoming Header | Departing NSH | | (also equal to | and Outer | | departing Inner | Headers | | Header) | | +-----------------+---------------+ | Not-ECT | ECT(0) | | ECT(0) | ECT(0) | | ECT(1) | ECT(1) | | CE | CE | +-----------------+---------------+ Table 2. Setting of ECN fields by an ingress/Classifier The requirements in this section apply to all ingress nodes for the domain in which NSH is being used to route traffic. INTERNET-DRAFT NSH ECN & Congestion Feedback 3.2 At Transit Nodes This section described behavior at nodes that forward based on the NSH such as SFF and other forwarding nodes such as IP routers. Figure 5 shows a packet on the wire between forwarding nodes. +-----------------+ | Outer Header | +-----------------+ | NSH | +-----------------+ | Inner Header | +-----------------+ | Payload | +-----------------+ Figure 5. Packet in Transit 3.2.1 At NSH Transit Nodes When a packet is received at an NSH based forwarding node N1, such as an SFF, the outer transport encapsulation is removed and its ECN marking SHOULD be combined into the NSH ECN marking as specified in [RFC6040]. If this is not done, any congestion encountered at non-NSH transit nodes between N1 and the next upstream NSH based forwarding node will be lost and not transmitted downstream. The NSH forwarding node SHOULD use a recognized AQM algorithm [RFC7567] to detect congestion. If the NSH ECN field indicates ECT, it will probabilistically set the NSH ECN field to the Congestion Experienced (CE) value or, in cases of extreme congestion, drop the packet. When the NSH encapsulated packet is further encapsulated for transmission to the next SFF or SF, ECN marking behavior depends on whether or not the node that will decapsulate the outer header supports Compliant ECN Decapsulation (see Section 3). If it does, then the ingress node propagates the NSH ECN field to this outer encapsulation using the "Normal Mode" of ECN encapsulation [RFC6040] (it copies the ECN field). If it does not, then the ingress MUST clear ECN in the outer encapsulation to non-ECT (the "Compatibility Mode" of [RFC6040]). INTERNET-DRAFT NSH ECN & Congestion Feedback 3.2.2 At an SF/Proxy If the SF is NSH and ECN-aware, the processing is essentially the same at the SF as at an SFF as discussed in Section 3.2.1. If the SF is NSH-aware but not ECN-aware, then the SFF transmitting the packet to the SF will use Compatibility Mode. Congestion encountered in the SFF to SF and SF to SFF paths will be unmanaged. If the SF is not NSH-aware, then an NSH proxy will be between the SFF and the SF to avoid exposure of the NSH at the SF that does not understand NSHs. This is described in Section 4.6 of [RFC7665]. The SF and proxy together look to the SFF like an NSH-aware SF. The behavior at the proxy and SF in this case is as below: If such a proxy is not ECN-aware then congestion in the entire path from SFF to proxy to SF back to proxy to SFF will be unmanaged. If the proxy is ECN-awareECN-aware, the proxy uses an AQM to indicate congestion inwithin the proxy itselfin the NSH that it returns to the SFF. The outer header used for the proxy to SF path uses Normal Mode. The outer head used for the proxy return to SFF path uses Normal Mode based copying the NSH ECN field to the outer header. Thus congestion in the proxy will be managed. Congestion in the SF will be managed only if the SF is ECN-aware implementing an AQM. 3.2.3 At Other Forwarding Nodes Other forwarding nodes, that is non-NSH forwarding nodes between NSH forwarding nodes, such as IP routers, might also contain potential bottlenecks. If so, they SHOULD implement an AQM algorithm to update the ECN marking in the outer transport header as specified in [RFC3168]. 3.3 At Exit/Egress First, any actions are taken based on Congestion Experienced, such as forwarding statistics back to the ingress (see Section 4). If the packet being carried inside the NSH is IP, when the NSH is removed the NSH ECN field MUST be combined with IP ECN field as specified in Table 3 that was extracted from [RFC6040]. This requirement applies to all egress nodes for the domain in which NSH is being used to route traffic. INTERNET-DRAFT NSH ECN & Congestion Feedback +---------+---------------------------------------------+ |Arriving | Arriving Outer Header | | Inner +---------+-----------+-----------+-----------+ | Header | Not-ECT | ECT(0) | ECT(1) | CE | +---------+---------+-----------+-----------+-----------+ | Not-ECT | Not-ECT |Not-ECT |Not-ECT | <drop> | | ECT(0) | ECT(0) | ECT(0) | ECT(0) | CE | | ECT(1) | ECT(1) | ECT(1) | ECT(1) | CE | | CE | CE | CE | CE | CE | +---------+---------+-----------+-----------+-----------+ Table 3. Exit ECN Fields Merger All the egress nodes of the SFC domain MUST support Compliant ECN Decapsulation as specified in this section. If this is not the case, the scheme described in this document will not work, and cannot be used. 3.4 Conservation of Packets The SFC specification permits an SF to absorb packets and to generate new packets as well as to process and forward the packets it receives. Such actions might appear to be packet loss due to congestion or might mask the loss of packets by generating additional packets. The tunnel congestion feedback approach [TunnelCongFeedback] detects loss by counting payload bytes in at the ingress and counting them out at the egress. This does not work unless nodes conserve the amount of payload bytes. Therefore, it will not be possible to detect loss using this technique if they are not conserved. Nonetheless, if a bottleneck supports ECN marking, it will be possible to detect the very high level of CE markings that are associated with congestion that is so excessive that it leads to loss. However, it will not be possible for the tunnel congestion feedback approach to detect any congestion, whether slight or severe, if it occurs at a bottleneck that does not support ECN marking. INTERNET-DRAFT NSH ECN & Congestion Feedback 4. Tunnel Congestion Feedback Support The collection and storage of congestion information may be useful for later analysis but, unless it can be fed back to a point which can take action to reduce congestion, it will not be useful in real time. Such congestion feedback to the ingress enables it to take actions such as those listed in Section 1.3. IP Flow Information Export (IPFIX [RFC7011]) provides a standard for communicating traffic flow statistics. As extended by [TunnelCongFeedback], IPFIX can be used to determine the extent of congestion between an ingress and egress. IPFIX recommends use of SCTP [RFC4960] in partial reliability mode. This mode allows loss of some packets, which is tolerable because IPFIX communicates cumulative statistics. IPFIX over SCTP SHOULD be used directly where there is IP connectivity between the ingress and egress; however, there might be different transport protocols or address spaces used in different regions of an SFC domain that make such direct IP connectivity problematic. The NSH provides the general method of routing of traffic within such domain so the IPFIX over SCTP over IP traffic should be encapsulated in NSH when necessary. INTERNET-DRAFT NSH ECN & Congestion Feedback 5. IANA Considerations IANA is requested to assign two contiguous bits in the NSH Base Header Bits registry for ECN (bits 16 and 17 suggested) and note this assignment as follows: Bit Description Reference ---------- ----------- --------------- tbd(16-17) NSH ECN [this document] INTERNET-DRAFT NSH ECN & Congestion Feedback 6. Security Considerations For general NSH security considerations, see [RFC8300]. For security considerations concerning tampering with ECN signaling, see [RFC3168]. For security considerations concerning ECN encapsulation, see [RFC6040]. For general IPFIX security considerations, see [RFC7011]. If deployed in an untrusted environment, the signaling traffic between ingress and egress can be protected utilizing the security mechanisms provided by IPFIX (see Section 11 in [RFC7011]). The solution in this document does not introduce any greater potential to invade privacy than would have been possible without the solution. 7. Acknowledgements The authors wish to thank the following for their comments and suggestion: Joel Halpern, Tal Mizrahi, Xinpeng Wei INTERNET-DRAFT NSH ECN & Congestion Feedback Normative References [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [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, <http://www.rfc- editor.org/info/rfc3168>. [RFC5129] - Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion Marking in MPLS", RFC 5129, DOI 10.17487/RFC5129, January 2008, <https://www.rfc-editor.org/info/rfc5129>. [RFC6040] - Briscoe, B., "Tunnelling of Explicit Congestion Notification", RFC 6040, DOI 10.17487/RFC6040, November 2010, <http://www.rfc-editor.org/info/rfc6040>. [RFC7011] - Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, September 2013, <https://www.rfc- editor.org/info/rfc7011>. [RFC7567] - Baker, F., Ed., and G. Fairhurst, Ed., "IETF Recommendations Regarding Active Queue Management", BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015, <http://www.rfc- editor.org/info/rfc7567>. [RFC8174] - Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <http://www.rfc-editor.org/info/rfc8174> [RFC8300] - Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., "Network Service Header (NSH)", RFC 8300, DOI 10.17487/RFC8300, January 2018, <https://www.rfc-editor.org/info/rfc8300>. [TunnelCongFeedback] - Wei, X., Li, Y., Boutros, S., and L. Deng, "Tunnel Congestion Feedback", draft-ietf-tsvwg-tunnel- congestion-feedback, work in progress. INTERNET-DRAFT NSH ECN & Congestion Feedback Informative References [RFC4301] - Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, December 2005, <https://www.rfc-editor.org/info/rfc4301>. [RFC4960] - Stewart, R., Ed., "Stream Control Transmission Protocol", RFC 4960, DOI 10.17487/RFC4960, September 2007, <https://www.rfc-editor.org/info/rfc4960>. [RFC7665] - Halpern, J., Ed., and C. Pignataro, Ed., "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015, <https://www.rfc- editor.org/info/rfc7665>. [RFC8311] - Black, D., "Relaxing Restrictions on Explicit Congestion Notification (ECN) Experimentation", RFC 8311, DOI 10.17487/RFC8311, January 2018, <https://www.rfc- editor.org/info/rfc8311>. [ecnL4S] - De Schepper, K., and B. Briscoe, "Identifying Modified Explicit Congestion Notification (ECN) Semantics for Ultra-Low Queuing Delay (L4S)", draft-ietf-tsvwg-ecn-l4s-id, work in progress. INTERNET-DRAFT NSH ECN & Congestion Feedback Authors' Addresses Donald E. Eastlake, 3rd Futurewei Technologies 2386 Panoramic Circle Apopka, FL 32703 USA Tel: +1-508-333-2270 Email: email@example.com Bob Briscoe Independent UK Email: firstname.lastname@example.org URI: http://bobbriscoe.net/ Andrew G. Malis Futurewei TechnologiesIndependent Email: email@example.com INTERNET-DRAFT NSH ECN & Congestion Feedback Copyright and IPR Provisions Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) 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. The definitive version of an IETF Document is that published by, or under the auspices of, the IETF. 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