--- 1/draft-ietf-tcpm-alternativebackoff-ecn-11.txt 2018-09-14 00:13:14.074770891 -0700 +++ 2/draft-ietf-tcpm-alternativebackoff-ecn-12.txt 2018-09-14 00:13:14.162773030 -0700 @@ -1,22 +1,22 @@ Network Working Group N. Khademi Internet-Draft M. Welzl Intended status: Experimental University of Oslo -Expires: March 4, 2019 G. Armitage +Expires: March 18, 2019 G. Armitage Netflix G. Fairhurst University of Aberdeen - August 31, 2018 + September 14, 2018 TCP Alternative Backoff with ECN (ABE) - draft-ietf-tcpm-alternativebackoff-ecn-11 + draft-ietf-tcpm-alternativebackoff-ecn-12 Abstract Active Queue Management (AQM) mechanisms allow for burst tolerance while enforcing short queues to minimise the time that packets spend enqueued at a bottleneck. This can cause noticeable performance degradation for TCP connections traversing such a bottleneck, especially if there are only a few flows or their bandwidth-delay- product is large. The reception of a Congestion Experienced (CE) ECN mark indicates that an AQM mechanism is used at the bottleneck, and @@ -36,21 +36,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on March 4, 2019. + This Internet-Draft will expire on March 18, 2019. Copyright Notice Copyright (c) 2018 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 (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -92,47 +92,48 @@ of ECN, but it is often relatively modest. Other benefits of deploying ECN have been documented in RFC8087 [RFC8087]. The rules for ECN were originally written to be very conservative, and required the congestion control algorithms of ECN-Capable transport protocols to treat indications of congestion signalled by ECN exactly the same as they would treat an inferred packet loss [RFC3168]. Research has demonstrated the benefits of reducing network delays that are caused by interaction of loss-based TCP congestion control and excessive buffering [BUFFERBLOAT]. This has - led to the creation of AQM mechanisms like PIE [RFC8033] and CoDel - [CODEL2012][RFC8289], which prevent bloated queues that are common - with unmanaged and excessively large buffers deployed across the - Internet [BUFFERBLOAT]. + led to the creation of AQM mechanisms like Proportional Integral + Controller Enhanced (PIE) [RFC8033] and Controlling Queue Delay + (CoDel) [CODEL2012][RFC8289], which prevent bloated queues that are + common with unmanaged and excessively large buffers deployed across + the Internet [BUFFERBLOAT]. The AQM mechanisms mentioned above aim to keep a sustained queue short while tolerating transient (short-term) packet bursts. However, currently used loss-based congestion control mechanisms are not always able to effectively utilise a bottleneck link where there are short queues. For example, a TCP sender using the Reno congestion control needs to be able to store at least an end-to-end bandwidth-delay product (BDP) worth of data at the bottleneck buffer if it is to maintain full path utilisation in the face of loss- - induced reduction of the congestion window (cwnd) [RFC5681], which - effectively doubles the amount of data that can be in flight, the - maximum round-trip time (RTT) experience, and the path's effective - RTT using the network path. + induced reduction of the congestion window (cwnd) [RFC5681]. This + amount of buffering effectively doubles the amount of data that can + be in flight and the maximum round-trip time (RTT) experienced by the + TCP sender. Modern AQM mechanisms can use ECN to signal the early signs of impending queue buildup long before a tail-drop queue would be forced to resort to dropping packets. It is therefore appropriate for the transport protocol congestion control algorithm to have a more measured response when it receives an indication with an early- warning of congestion after the remote endpoint receives an ECN CE- marked packet. Recognizing these changes in modern AQM practices, the strict requirement that ECN CE signals be treated identically to - inferred packet loss have been relaxed [RFC8311]. This document + inferred packet loss has been relaxed [RFC8311]. This document therefore defines a new sender-side-only congestion control response, called "ABE" (Alternative Backoff with ECN). ABE improves TCP's average throughput when routers use AQM controlled buffers that allow only for short queues. 2. Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP @@ -396,20 +397,22 @@ mechanisms that have been in use in the Internet for many years (e.g., CUBIC [RFC8312]). Unfairness may also be a result of other factors, including the round trip time experienced by a flow. ABE applies only when ECN-marked packets are received, not when packets are lost, hence use of ABE cannot lead to congestion collapse. 11. Revision Information XX RFC ED - PLEASE REMOVE THIS SECTION XXX + -12. Corrections from Adam Roach; Benjamin Kaduk; & Ben Campbell + -10. Incorported changes following the Gen-ART review by Russ Housley. Correction to URL. -09. Changed to "Following publication of RFC 8311, this document specifies a sender-side change to TCP:" -08. Addressed comments from AD review on the document structure, and relationship to existing RFCs. -07. Addressed comments following WGLC. @@ -512,41 +515,39 @@ . [ABE2017] Khademi, N., Armitage, G., Welzl, M., Fairhurst, G., Zander, S., and D. Ros, "Alternative Backoff: Achieving Low Latency and High Throughput with ECN and AQM", IFIP NETWORKING 2017, Stockholm, Sweden, June 2017. [BUFFERBLOAT] Gettys, J. and K. Nichols, "Bufferbloat: Dark Buffers in - the Internet", November 2011. + the Internet", ACM Queue 9, 11, DOI + 10.1145/2063166.2071893; + https://queue.acm.org/detail.cfm?id=2071893", November + 2011. [CODEL2012] Nichols, K. and V. Jacobson, "Controlling Queue Delay", July 2012, . [I-D.ietf-tcpm-accurate-ecn] Briscoe, B., Kuehlewind, M., and R. Scheffenegger, "More Accurate ECN Feedback in TCP", draft-ietf-tcpm-accurate- ecn-06 (work in progress), March 2018. [ICC2002] Kwon, M. and S. Fahmy, "TCP Increase/Decrease Behavior with Explicit Congestion Notification (ECN)", IEEE ICC 2002, New York, New York, USA, May 2002, . - [RFC7713] Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx) - Concepts, Abstract Mechanism, and Requirements", RFC 7713, - DOI 10.17487/RFC7713, December 2015, - . - [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, . [RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using Explicit Congestion Notification (ECN)", RFC 8087, DOI 10.17487/RFC8087, March 2017, .