rfc7560v4.txt   rfc7560.txt 
Internet Engineering Task Force (IETF) M. Kuehlewind, Ed. Internet Engineering Task Force (IETF) M. Kuehlewind, Ed.
Request for Comments: 7560 ETH Zurich Request for Comments: 7560 ETH Zurich
Category: Informational R. Scheffenegger Category: Informational R. Scheffenegger
ISSN: 2070-1721 NetApp, Inc. ISSN: 2070-1721 NetApp, Inc.
B. Briscoe B. Briscoe
BT BT
July 2015 August 2015
Problem Statement and Requirements for Increased Accuracy Problem Statement and Requirements for Increased Accuracy
in Explicit Congestion Notification (ECN) Feedback in Explicit Congestion Notification (ECN) Feedback
Abstract Abstract
Explicit Congestion Notification (ECN) is a mechanism where network Explicit Congestion Notification (ECN) is a mechanism where network
nodes can mark IP packets, instead of dropping them, to indicate nodes can mark IP packets, instead of dropping them, to indicate
congestion to the endpoints. An ECN-capable receiver will feed this congestion to the endpoints. An ECN-capable receiver will feed this
information back to the sender. ECN is specified for TCP in such a information back to the sender. ECN is specified for TCP in such a
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Recap of Classic ECN and ECN Nonce in IP/TCP . . . . . . . . 4 2. Recap of Classic ECN and ECN Nonce in IP/TCP . . . . . . . . 5
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Design Approaches . . . . . . . . . . . . . . . . . . . . . . 10 5. Design Approaches . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Redefinition of ECN/NS Header Bits . . . . . . . . . . . 11 5.1. Redefinition of ECN/NS Header Bits . . . . . . . . . . . 11
5.2. Using Other Header Bits . . . . . . . . . . . . . . . . . 12 5.2. Using Other Header Bits . . . . . . . . . . . . . . . . . 13
5.3. Using a TCP Option . . . . . . . . . . . . . . . . . . . 12 5.3. Using a TCP Option . . . . . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . 13 7.1. Normative References . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . 14 7.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Ambiguity of the More Accurate ECN Feedback in DCTCP 15 Appendix A. Ambiguity of the More Accurate ECN Feedback in DCTCP 16
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
Explicit Congestion Notification (ECN) [RFC3168] is a mechanism where Explicit Congestion Notification (ECN) [RFC3168] is a mechanism where
network nodes can mark IP packets instead of dropping them to network nodes can mark IP packets instead of dropping them to
indicate congestion to the endpoints. An ECN-capable receiver will indicate congestion to the endpoints. An ECN-capable receiver will
feed this information back to the sender. ECN is specified for TCP feed this information back to the sender. ECN is specified for TCP
in such a way that only one feedback signal can be transmitted per in such a way that only one feedback signal can be transmitted per
Round-Trip Time (RTT). This is sufficient for preexisting TCP Round-Trip Time (RTT). This is sufficient for preexisting TCP
congestion control mechanisms that perform only one reduction in congestion control mechanisms that perform only one reduction in
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connections consuming excess sender or network resources. This connections consuming excess sender or network resources. This
problem is similar to that seen with the classic ECN feedback scheme problem is similar to that seen with the classic ECN feedback scheme
and should be addressed by integrity checking as required in and should be addressed by integrity checking as required in
Section 4. Section 4.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP", RFC of Explicit Congestion Notification (ECN) to IP",
3168, DOI 10.17487/RFC3168, September 2001, RFC 3168, DOI 10.17487/RFC3168, September 2001,
<http://www.rfc-editor.org/info/rfc3168>. <http://www.rfc-editor.org/info/rfc3168>.
[RFC3540] Spring, N., Wetherall, D., and D. Ely, "Robust Explicit [RFC3540] Spring, N., Wetherall, D., and D. Ely, "Robust Explicit
Congestion Notification (ECN) Signaling with Nonces", RFC Congestion Notification (ECN) Signaling with Nonces",
3540, DOI 10.17487/RFC3540, June 2003, RFC 3540, DOI 10.17487/RFC3540, June 2003,
<http://www.rfc-editor.org/info/rfc3540>. <http://www.rfc-editor.org/info/rfc3540>.
7.2. Informative References 7.2. Informative References
[DCTCP] Bensley, S., Eggert, L., and D. Thaler, "Microsoft's [DCTCP] Bensley, S., Eggert, L., and D. Thaler, "Microsoft's
Datacenter TCP (DCTCP): TCP Congestion Control for Datacenter TCP (DCTCP): TCP Congestion Control for
Datacenters", Work in Progress, draft-bensley-tcpm-dctcp- Datacenters", Work in Progress,
03, April 2015. draft-bensley-tcpm-dctcp-05, July 2015.
[ECN-BENEFITS] [ECN-BENEFITS]
Fairhurst, G. and M. Welzl, "The Benefits of using Fairhurst, G. and M. Welzl, "The Benefits of using
Explicit Congestion Notification (ECN)", Work in Progress Explicit Congestion Notification (ECN)", Work in Progress
draft-ietf-aqm-ecn-benefits-04, May 2015. draft-ietf-aqm-ecn-benefits-06, July 2015.
[RFC0896] Nagle, J., "Congestion Control in IP/TCP Internetworks", [RFC0896] Nagle, J., "Congestion Control in IP/TCP Internetworks",
RFC 896, DOI 10.17487/RFC0896, January 1984, RFC 896, DOI 10.17487/RFC0896, January 1984,
<http://www.rfc-editor.org/info/rfc896>. <http://www.rfc-editor.org/info/rfc896>.
[RFC2018] Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP [RFC2018] Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP
Selective Acknowledgment Options", RFC 2018, DOI 10.17487/ Selective Acknowledgment Options", RFC 2018,
RFC2018, October 1996, DOI 10.17487/RFC2018, October 1996,
<http://www.rfc-editor.org/info/rfc2018>. <http://www.rfc-editor.org/info/rfc2018>.
[RFC3449] Balakrishnan, H., Padmanabhan, V., Fairhurst, G., and M. [RFC3449] Balakrishnan, H., Padmanabhan, V., Fairhurst, G., and M.
Sooriyabandara, "TCP Performance Implications of Network Sooriyabandara, "TCP Performance Implications of Network
Path Asymmetry", BCP 69, RFC 3449, DOI 10.17487/RFC3449, Path Asymmetry", BCP 69, RFC 3449, DOI 10.17487/RFC3449,
December 2002, <http://www.rfc-editor.org/info/rfc3449>. December 2002, <http://www.rfc-editor.org/info/rfc3449>.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009, Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<http://www.rfc-editor.org/info/rfc5681>. <http://www.rfc-editor.org/info/rfc5681>.
[RFC5690] Floyd, S., Arcia, A., Ros, D., and J. Iyengar, "Adding [RFC5690] Floyd, S., Arcia, A., Ros, D., and J. Iyengar, "Adding
Acknowledgement Congestion Control to TCP", RFC 5690, DOI Acknowledgement Congestion Control to TCP", RFC 5690,
10.17487/RFC5690, February 2010, DOI 10.17487/RFC5690, February 2010,
<http://www.rfc-editor.org/info/rfc5690>. <http://www.rfc-editor.org/info/rfc5690>.
[RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the [RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the
TCP Urgent Mechanism", RFC 6093, DOI 10.17487/RFC6093, TCP Urgent Mechanism", RFC 6093, DOI 10.17487/RFC6093,
January 2011, <http://www.rfc-editor.org/info/rfc6093>. January 2011, <http://www.rfc-editor.org/info/rfc6093>.
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
and K. Carlberg, "Explicit Congestion Notification (ECN) and K. Carlberg, "Explicit Congestion Notification (ECN)
for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August
2012, <http://www.rfc-editor.org/info/rfc6679>. 2012, <http://www.rfc-editor.org/info/rfc6679>.
[RFC6789] Briscoe, B., Ed., Woundy, R., Ed., and A. Cooper, Ed., [RFC6789] Briscoe, B., Ed., Woundy, R., Ed., and A. Cooper, Ed.,
"Congestion Exposure (ConEx) Concepts and Use Cases", RFC "Congestion Exposure (ConEx) Concepts and Use Cases",
6789, DOI 10.17487/RFC6789, December 2012, RFC 6789, DOI 10.17487/RFC6789, December 2012,
<http://www.rfc-editor.org/info/rfc6789>. <http://www.rfc-editor.org/info/rfc6789>.
[SCTP-ECN] [SCTP-ECN]
Stewart, R., Tuexen, M., and X. Dong, "ECN for Stream Stewart, R., Tuexen, M., and X. Dong, "ECN for Stream
Control Transmission Protocol (SCTP)", Work in Progress, Control Transmission Protocol (SCTP)", Work in Progress,
draft-stewart-tsvwg-sctpecn-05, January 2014. draft-stewart-tsvwg-sctpecn-05, January 2014.
[TEST-RCV] [TEST-RCV]
Moncaster, T., Briscoe, B., and A. Jacquet, "A TCP Test to Moncaster, T., Briscoe, B., and A. Jacquet, "A TCP Test to
Allow Senders to Identify Receiver Non-Compliance", Work Allow Senders to Identify Receiver Non-Compliance", Work
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