[Docs] [txt|pdf|xml|html] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01

Network Working Group                                         N. Khademi
Internet-Draft                                                  M. Welzl
Updates: 3168,4774 (if approved)                      University of Oslo
Intended status: Standards Track                             G. Armitage
Expires: January 21, 2017                        Swinburne University of
                                                              Technology
                                                            G. Fairhurst
                                                  University of Aberdeen
                                                           July 20, 2016


  Updating the Explicit Congestion Notification (ECN) Specification to
                       Allow IETF Experimentation
                  draft-khademi-tsvwg-ecn-response-01

Abstract

   This document relaxes recommendations and prescriptions from RFC3168
   and RFC4774 that get in the way of experimentation with different ECN
   strategies.  First, RFC3168 and RFC4774 state that, upon the receipt
   by an ECN-Capable transport of a single CE packet, the congestion
   control algorithms followed at the end-systems MUST be essentially
   the same as the congestion control response to a single dropped
   packet.  This document relaxes this rule in order to encourage
   experimentation with different backoff strategies.  Second, this
   document allows future IETF specifications to use the ECT(1)
   codepoint in ways that are currently prohibited by RFC3168.  Third,
   this document allows future IETF experiments to use the ECT(0) or
   ECT(1) codepoint on any TCP segment.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   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 http://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 January 21, 2017.

Copyright Notice



Khademi, et al.         Expires January 21, 2017                [Page 1]


Internet-Draft                ECN-response                     July 2016


   Copyright (c) 2016 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.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Differently reacting to ECN-marks and loss . . . . . . . .  3
       1.1.1.  Discussion: Why Use ECN to Vary the Degree of
               Backoff? . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Senders setting the ECT(1) codepoint . . . . . . . . . . .  5
     1.3.  ECT(0) and ECT(1) on control packets . . . . . . . . . . .  5
   2.  Updating RFC3168 and RFC4774 . . . . . . . . . . . . . . . . .  5
     2.1.  RFC 2119 . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Scope of this update . . . . . . . . . . . . . . . . . . .  6
     2.3.  Changes to the meaning of a CE-Mark codepoint  . . . . . .  6
     2.4.  Setting ECT(0) and ECT(1) Codepoints . . . . . . . . . . .  7
     2.5.  Clarification to the usage of the ECT(1) Codepoint . . . .  7
   3.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   6.  Revision Information . . . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11















Khademi, et al.         Expires January 21, 2017                [Page 2]


Internet-Draft                ECN-response                     July 2016


1.  Introduction

   This document relaxes three limitations that are due to specific text
   in [RFC3168] and, in one case, also [RFC4774].

1.1.  Differently reacting to ECN-marks and loss

   Explicit Congestion Notification (ECN) as specified in [RFC3168]
   allows a network device that uses Active Queue Management (AQM) to
   set the Congestion Experienced (CE) codepoint in the ECN field of the
   IP packet header, rather than to drop ECN-capable packets when
   incipient congestion is detected.  When an ECN-capable transport is
   used over a path that supports ECN, this provides the opportunity for
   flows to improve their performance in the presence of incipient
   congestion [I-D.AQM-ECN-benefits].

   [RFC3168] not only specifies the router use of the ECN field, it also
   specifies a TCP procedure for using ECN.  This states that a TCP
   sender should treat the ECN indication of congestion in the same way
   as that of a non-ECN-Capable TCP flow experiencing loss, by halving
   the congestion window "cwnd" and by reducing the slow start threshold
   "ssthresh".  [RFC5681] stipulates that TCP congestion control sets
   "ssthresh" to max(FlightSize / 2, 2*SMSS) in response to packet loss.
   This corresponds to a backoff multiplier of 0.5 (halving cwnd and
   sshthresh after packet loss).  Consequently, a standard TCP flow
   using this reaction needs significant network queue space: it can
   only fully utilise a bottleneck when the length of the link queue (or
   the AQM dropping threshold) is at least the bandwidth-delay product
   (BDP) of the flow.

   A backoff multiplier of 0.5 is not the only available strategy.  As
   defined in [I-D.CUBIC], CUBIC multiplies the current cwnd by 0.7 in
   response to loss ( the Linux implementation of CUBIC has used a
   multiplier of 0.7 since kernel version 2.6.25 released in 2008).
   Consequently, CUBIC utilises paths well even when the bottleneck
   queue is shorter than the bandwidth-delay product of the flow.
   However, in the case of a DropTail (FIFO) queue without AQM, such
   less-aggressive backoff increases the risk of creating a standing
   queue [CODEL2012].

   Devices implementing AQM are likely to be the dominant (and possibly
   only) source of ECN CE-marking for packets from ECN-capable senders.
   AQM mechanisms typically strive to maintain a small average queue
   length, regardless of the bandwidth-delay product of flows passing
   through them.  Receipt of an ECN CE-mark might therefore reasonably
   be taken to indicate that a small bottleneck queue exists in the
   path, and hence the TCP flow would benefit from using a less
   aggressive backoff multiplier.  Such behavior is however prohibited



Khademi, et al.         Expires January 21, 2017                [Page 3]


Internet-Draft                ECN-response                     July 2016


   by the rules in [RFC3168].

   ECN has seen little deployment so far.  Apple recently announced
   their intention to enable ECN in iOS 9 and OS X 10.11 devices
   [WWDC2015].  By 2014, server-side ECN negotiation was observed to be
   provided by the majority of the top million web servers [PAM2015],
   and only 0.5% of websites incurred additional connection setup
   latency using RFC3168-compliant ECN-fallback mechanisms.  [RFC7567]
   states that "deployed AQM algorithms SHOULD support Explicit
   Congestion Notification (ECN) as well as loss to signal congestion to
   endpoints" and [I-D.AQM-ECN-benefits] encourages this deployment.
   However, the limitation of [RFC3168] restricts a sender to react to
   notification of a CE-mark in the same way as if a packet was lost.
   This prohibits experimentation with ECN mechanisms that could yield
   greater benefits.  This specification therefore relaxes this
   constraint.

1.1.1.  Discussion: Why Use ECN to Vary the Degree of Backoff?

   The classic rule-of-thumb dictates that a transport provides a BDP of
   bottleneck buffering if a TCP connection wishes to optimise path
   utilisation.  A single TCP connection running through such a
   bottleneck will have opened cwnd up to 2*BDP by the time packet loss
   occurs.  [RFC5681]'s halving of cwnd and ssthresh pushes the TCP
   connection back to allowing only a BDP of packets in flight -- just
   sufficient to maintain 100% utilisation of the network path.

   AQM schemes like CoDel [I-D.CoDel] and PIE [I-D.PIE] use congestion
   notifications to constrain the queuing delays experienced by packets,
   rather than in response to impending or actual bottleneck buffer
   exhaustion.  With current default delay targets, CoDel and PIE both
   effectively emulate a shallow buffered bottleneck (section II,
   [ABE2015]) while allowing short traffic bursts into the queue.  This
   interacts acceptably for TCP connections over low BDP paths, or
   highly multiplexed scenarios (many concurrent TCP connections).
   However, it interacts badly with lightly-multiplexed cases (few
   concurrent connections) over a high BDP path.  Conventional TCP
   backoff in such cases leads to gaps in packet transmission and under-
   utilisation of the path.

   The idea to react differently to loss upon detecting an ECN CE-mark
   pre-dates [ABE2015].  [ICC2002] also proposed using ECN CE-marks to
   modify TCP congestion control behaviour, using a larger
   multiplicative decrease factor in conjunction with a smaller additive
   increase factor to work with RED-based bottlenecks that were not
   necessarily configured to emulate a shallow queue.

   This update to [RFC3168] that enables the IETF to specify experiments



Khademi, et al.         Expires January 21, 2017                [Page 4]


Internet-Draft                ECN-response                     July 2016


   with a different backoff behavior in response to a CE-mark than in
   response to packet loss is utilized by an experiment called
   "Alternative Backoff with ECN" (ABE).  ABE is based upon [ABE2015]
   and defined in [I-D.ABE].

1.2.  Senders setting the ECT(1) codepoint

   Future IETF experiments may require setting the ECT(0) or ECT(1)
   codepoints differently from what [RFC3168] recommends or requires.

   [NOTE: This usage was also specified in ECN-NONCE.]

   This update may also allow the iETF to specify future mechanisms that
   associate alternate ECN semantics with this codepoint.  An experiment
   called "L4S" proposes to use the ECT(1) codepoint to indicate in
   which of two queues a packet should be placed
   [I-D.briscoe-tsvwg-ecn-l4s-id].

1.3.  ECT(0) and ECT(1) on control packets

   Diverging from recommendations or requirements in [RFC3168], future
   IETF experiments may be specified to use the ECT(0) or ECT(1)
   codepoint.  This choice of codepoint can be used to signal
   alternative ECN semantics.  This supersedes the rationale in Section
   20 of [RFC3168] that argued against the use of ECT(1) to specify
   alternate ECN semantics, instead arguing for attaching specific ECN
   semantics to a Differentiated Services Code Point (DSCP).

   This update may also allow the iETF to specify future updates to
   transport protocol use of ECN.  A
   proposal,[I-D.bagnulo-tsvwg-generalized-ecn], provides arguments for
   using the ECT(0) or ECT(1) codepoint on a broader range of TCP
   packets for which such usage is precluded by [RFC3168]: SYNs, pure
   ACKs, retransmitted packets and window probe packets.


2.  Updating RFC3168 and RFC4774

   This section specifies updates to [RFC3168] (and corresponding text
   in [RFC4774]) and refers to experiments that are possible within the
   framework provided by the update.

2.1.  RFC 2119

   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].




Khademi, et al.         Expires January 21, 2017                [Page 5]


Internet-Draft                ECN-response                     July 2016


2.2.  Scope of this update

   Internet deployment of new mechanisms enabled by this update REQUIRE
   IETF specification in an Experimental or a Standards Track RFC
   approved by the IESG.

   Some mechanisms rely on ECN semantics that differ from the
   definitions in [RFC3168] -- for example, Congestion Exposure (ConEx)
   [RFC7713] and DCTCP [I-D.ietf-tcpm-dctcp] need more accurate ECN
   information than the feedback mechanism in [RFC3168] offers (defined
   in [I-D.ietf-tcpm-accurate-ecn]).  Such mechanisms allow a sending
   rate adjustment more frequent than each RTT.  These mechanisms are
   out of the scope of the current document.

   The remainder of this section lists a set of changes to [RFC3168]
   that are not specific replacements of text passages.

2.3.  Changes to the meaning of a CE-Mark codepoint

   This document specifies an update to the TCP sender reaction that
   follows when the TCP receiver signals that ECN CE-marked packets have
   been received.

   [RFC3168] and [RFC4774] contain the following text:

   "Upon the receipt by an ECN-Capable transport of a single CE packet,
   the congestion control algorithms followed at the end-systems MUST be
   essentially the same as the congestion control response to a *single*
   dropped packet.  For example, for ECN-Capable TCP the source TCP is
   required to halve its congestion window for any window of data
   containing either a packet drop or an ECN indication."

   This memo updates the preceding text by replacing it with the
   following text:

   "Upon the receipt by an ECN-Capable transport of a single CE-Marked
   packet, the congestion control algorithms followed at the endpoints
   MUST make a congestion control response as specified in [RFC3168] or
   its updates.  For example, an ECN-Capable TCP sender could halve its
   congestion window for any window of data containing either a packet
   drop or an ECN indication."

   The first paragraph of Section 6.1.2, "The TCP Sender", in [RFC3168]
   contains the following text:

   "If the sender receives an ECN-Echo (ECE) ACK packet (that is, an ACK
   packet with the ECN-Echo flag set in the TCP header), then the sender
   knows that congestion was encountered in the network on the path from



Khademi, et al.         Expires January 21, 2017                [Page 6]


Internet-Draft                ECN-response                     July 2016


   the sender to the receiver.  The indication of congestion should be
   treated just as a congestion loss in non-ECN-Capable TCP.  That is,
   the TCP source halves the congestion window "cwnd" and reduces the
   slow start threshold "ssthresh"."

   This memo updates the preceding text by replacing it with the
   following text:

   "If a TCP sender receives an indication of a receibed ECN-Echo (ECE)
   ACK packet (that is, an ACK packet with the ECN-Echo flag set in the
   TCP header), then the sender knows that congestion was encountered in
   the network on the path from the sender to the receiver.  An
   indication of congestion, signalled by reception of the ECN-Echo flag
   (with the semantics defined in [RFC3168]) MUST produce a rate
   reduction of at least 15%, so that flows sharing the same bottleneck
   can increase their share of the capacity.  The indication of
   congestion could be treated in the same way as if the flow had
   experienced loss, but future congestion control methods are allowed
   to specify a reduction that is less than the reduction for congestion
   loss.

   An ECN-capable network device cannot eliminate the possibility of
   packet loss.  A drop may still occur due to a traffic burst exceeding
   the instantaneous available capacity of a network buffer or as a
   result of the AQM algorithm (overload protection mechanisms, etc
   [RFC7567]).  Whatever the cause of loss, detection of a missing
   packet needs to trigger the standard loss-based congestion control
   response".  This update explicitly does not change the use of
   standard protocol mechanisms following loss, as required in
   [RFC3168].

2.4.  Setting ECT(0) and ECT(1) Codepoints

   New IETF specifications MAY permit a sender to set the ECT(0) or
   ECT(1) codepoint on a protocol control packet (including TCP segments
   for which [RFC3168] does not allow or recommend setting these
   codepoints.)

   [AUTHORS' NOTE: Future versions of this document may take the form of
   such explicit text replacements.]

2.5.  Clarification to the usage of the ECT(1) Codepoint

   [RFC3168] notes that a router may treat and mark/drop packets
   differently depending on whether they observe the ECT(0) or ECT(1)
   codepoint.  This specification permits new IETF specifications to set
   or read the ECT(1) codepeoint.  It clarifies that these
   specifications do not necessarily treat ECT(1) as equivalent to



Khademi, et al.         Expires January 21, 2017                [Page 7]


Internet-Draft                ECN-response                     July 2016


   ECT(0).

   Network devices using IETF-defined DSCPs MUST NOT re-mark packets to
   the ECT(1) codepoint.  Specifically, the methods described in earlier
   ECN implementations using this codepoint as a congestion mark
   (described in Section 11.2.1 of [RFC3168]) are NOT RECOMMENDED for
   deployment in the current Internet.


3.  Acknowledgements

   The authors N. Khademi, M. Welzl and G. Fairhurst were part-funded by
   the European Community under its Seventh Framework Programme through
   the Reducing Internet Transport Latency (RITE) project (ICT-317700).
   The views expressed are solely those of the authors.


4.  IANA Considerations

   XX RFC ED - PLEASE REMOVE THIS SECTION XXX

   This memo includes no request to IANA.


5.  Security Considerations

   The described method is a sender-side only transport change, and does
   not change the protocol messages exchanged.  The security
   considerations of [RFC3168] therefore still apply.

   A congestion control backoff that is less in response to ECN than the
   response to a packet loss can lead to a change in the capacity
   achieved when flows share a network bottleneck.  This can result in
   redistribution of capacity between sharing flows, potentially
   resulting in unfairness in the way that capacity is shared.  This
   potential gain applies only to ECN-marked packets using the updated
   method (and not to detected packet loss).  Similar unfairness can be
   exhibited by congestion control mechanisms that have been used in the
   Internet for many years (e.g., CUBIC [I-D.CUBIC]).  Unfairness may
   also be a result of other factors, including the round trip time
   experienced by a flow.

   Packet loss can be expected from an AQM algorithm experiencing
   persistent queuing, but could also imply the presence of faulty
   equipment or media in a path, or it may imply the presence of
   congestion [RFC7567].  The update does not change the congestion
   control response to packet loss, and will therefore not lead to
   congestion collapse.



Khademi, et al.         Expires January 21, 2017                [Page 8]


Internet-Draft                ECN-response                     July 2016


   [AUTHORS' NOTE: Security considerations of the more relaxed rules of
   using ECT(0) vs. ECT(1) and usage of these ECT codepoints on any TCP
   segments will be included in the next version of this document.]


6.  Revision Information

   XX RFC ED - PLEASE REMOVE THIS SECTION XXX

   -01.  Broadened the scope to also cover ECT(0) vs. ECT(1) usage and
   using ECT(0) or ECT(1) codepoints on any TCP segments.

   -00. draft-khademi-tsvwg-ecn-response-00 and
   draft-khademi-tcpm-alternativebackoff-ecn-00 replace
   draft-khademi-alternativebackoff-ecn-03, following discussion in the
   TSVWG and TCPM working groups.


7.  References

7.1.  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>.

   [RFC4774]  Floyd, S., "Specifying Alternate Semantics for the
              Explicit Congestion Notification (ECN) Field", BCP 124,
              RFC 4774, DOI 10.17487/RFC4774, November 2006,
              <http://www.rfc-editor.org/info/rfc4774>.

   [RFC5681]  Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
              Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
              <http://www.rfc-editor.org/info/rfc5681>.

   [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>.






Khademi, et al.         Expires January 21, 2017                [Page 9]


Internet-Draft                ECN-response                     July 2016


7.2.  Informative References

   [ABE2015]  Khademi, N., Welzl, M., Armitage, G., Kulatunga, C., Ros,
              D., Fairhurst, G., Gjessing, S., and S. Zander,
              "Alternative Backoff: Achieving Low Latency and High
              Throughput with ECN and AQM", CAIA Technical Report CAIA-
              TR-150710A, Swinburne University of Technology, July 2015,
              <http://caia.swin.edu.au/reports/150710A/
              CAIA-TR-150710A.pdf>.

   [CODEL2012]
              Nichols, K. and V. Jacobson, "Controlling Queue Delay",
              July 2012, <http://queue.acm.org/detail.cfm?id=2209336>.

   [I-D.ABE]  Khademi, N., Welzl, M., Armitage, G., and G. Fairhurst,
              "TCP Alternative Backoff with ECN (ABE)", Internet-draft,
              IETF work-in-progress draft-khademi-tcpm-
              alternativebackoff-ecn-00, May 2016.

   [I-D.AQM-ECN-benefits]
              Fairhurst, G. and M. Welzl, "The Benefits of using
              Explicit Congestion Notification (ECN)", Internet-draft,
              IETF work-in-progress draft-ietf-aqm-ecn-benefits-08,
              November 2015.

   [I-D.CUBIC]
              Rhee, I., Xu, L., Ha, S., Zimmermann, A., Eggert, L., and
              R. Scheffenegger, "CUBIC for Fast Long-Distance Networks",
              Internet-draft, IETF
              work-in-progress draft-ietf-tcpm-cubic-01, January 2016.

   [I-D.CoDel]
              Nichols, K., Jacobson, V., McGregor, V., and J. Iyengar,
              "Controlled Delay Active Queue Management", Internet-
              draft, IETF work-in-progress draft-ietf-aqm-codel-03,
              March 2016.

   [I-D.PIE]  Pan, R., Natarajan, P., Baker, F., White, G., VerSteeg,
              B., Prabhu, M., Piglione, C., and V. Subramanian, "PIE: A
              Lightweight Control Scheme To Address the Bufferbloat
              Problem", Internet-draft, IETF
              work-in-progress draft-ietf-aqm-pie-07, April 2016.

   [I-D.bagnulo-tsvwg-generalized-ecn]
              Bagnulo, M. and B. Briscoe, "Adding Explicit Congestion
              Notification (ECN) to TCP control packets",
              draft-bagnulo-tsvwg-generalized-ecn-01 (work in progress),
              July 2016.



Khademi, et al.         Expires January 21, 2017               [Page 10]


Internet-Draft                ECN-response                     July 2016


   [I-D.briscoe-tsvwg-ecn-l4s-id]
              Schepper, K., Briscoe, B., and I. Tsang, "Identifying
              Modified Explicit Congestion Notification (ECN) Semantics
              for Ultra-Low Queuing Delay",
              draft-briscoe-tsvwg-ecn-l4s-id-01 (work in progress),
              March 2016.

   [I-D.ietf-tcpm-accurate-ecn]
              Briscoe, B., Kuehlewind, M., and R. Scheffenegger, "More
              Accurate ECN Feedback in TCP",
              draft-ietf-tcpm-accurate-ecn-00 (work in progress),
              December 2015.

   [I-D.ietf-tcpm-dctcp]
              Bensley, S., Eggert, L., Thaler, D., Balasubramanian, P.,
              and G. Judd, "Datacenter TCP (DCTCP): TCP Congestion
              Control for Datacenters", draft-ietf-tcpm-dctcp-01 (work
              in progress), November 2015.

   [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,
              <http://dx.doi.org/10.1109/ICC.2002.997262>.

   [PAM2015]  Trammell, B., Kuhlewind, M., Boppart, D., Learmonth, I.,
              Fairhurst, G., and R. Scheffenegger, "Enabling Internet-
              wide Deployment of Explicit Congestion Notification",
              Proceedings of the 2015 Passive and Active Measurement
              Conference, New York, March 2015,
              <http://ecn.ethz.ch/ecn-pam15.pdf>.

   [RFC7713]  Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx)
              Concepts, Abstract Mechanism, and Requirements", RFC 7713,
              DOI 10.17487/RFC7713, December 2015,
              <http://www.rfc-editor.org/info/rfc7713>.

   [WWDC2015]
              Lakhera, P. and S. Cheshire, "Your App and Next Generation
              Networks", Apple Worldwide Developers Conference 2015, San
              Francisco, USA, June 2015,
              <https://developer.apple.com/videos/wwdc/2015/?id=719>.










Khademi, et al.         Expires January 21, 2017               [Page 11]


Internet-Draft                ECN-response                     July 2016


Authors' Addresses

   Naeem Khademi
   University of Oslo
   PO Box 1080 Blindern
   Oslo,   N-0316
   Norway

   Email: naeemk@ifi.uio.no


   Michael Welzl
   University of Oslo
   PO Box 1080 Blindern
   Oslo,   N-0316
   Norway

   Email: michawe@ifi.uio.no


   Grenville Armitage
   Centre for Advanced Internet Architectures
   Swinburne University of Technology
   PO Box 218
   John Street, Hawthorn
   Victoria,   3122
   Australia

   Email: garmitage@swin.edu.au


   Godred Fairhurst
   University of Aberdeen
   School of Engineering, Fraser Noble Building
   Aberdeen,   AB24 3UE
   UK

   Email: gorry@erg.abdn.ac.uk













Khademi, et al.         Expires January 21, 2017               [Page 12]


Html markup produced by rfcmarkup 1.123, available from https://tools.ietf.org/tools/rfcmarkup/