Open Research Issues in Internet Congestion Control
RFC 6077

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Internet Research Task Force (IRTF)                D. Papadimitriou, Ed.
Request for Comments: 6077                                Alcatel-Lucent
Category: Informational                                         M. Welzl
ISSN: 2070-1721                                       University of Oslo
                                                               M. Scharf
                                                 University of Stuttgart
                                                              B. Briscoe
                                                                BT & UCL
                                                           February 2011

          Open Research Issues in Internet Congestion Control

Abstract

   This document describes some of the open problems in Internet
   congestion control that are known today.  This includes several new
   challenges that are becoming important as the network grows, as well
   as some issues that have been known for many years.  These challenges
   are generally considered to be open research topics that may require
   more study or application of innovative techniques before Internet-
   scale solutions can be confidently engineered and deployed.

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 Research Task Force
   (IRTF).  The IRTF publishes the results of Internet-related research
   and development activities.  These results might not be suitable for
   deployment.  This RFC represents the consensus of the Internet
   Congestion Control Research Group (ICCRG) of the Internet Research
   Task Force (IRTF).  Documents approved for publication by the IRSG
   are not a candidate for any level of Internet Standard; see Section 2
   of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6077.

Papadimitriou, et al.         Informational                     [Page 1]
RFC 6077       Open Issues in Internet Congestion Control  February 2011

Copyright Notice

   Copyright (c) 2011 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.

Papadimitriou, et al.         Informational                     [Page 2]
RFC 6077       Open Issues in Internet Congestion Control  February 2011

Table of Contents

   1. Introduction ....................................................3
   2. Global Challenges ...............................................5
      2.1. Heterogeneity ..............................................5
      2.2. Stability ..................................................7
      2.3. Fairness ...................................................8
   3. Detailed Challenges ............................................10
      3.1. Challenge 1: Network Support ..............................10
           3.1.1. Performance and Robustness .........................14
           3.1.2. Granularity of Network Component Functions .........15
           3.1.3. Information Acquisition ............................16
           3.1.4. Feedback Signaling .................................17
      3.2. Challenge 2: Corruption Loss ..............................17
      3.3. Challenge 3: Packet Size ..................................19
      3.4. Challenge 4: Flow Startup .................................24
      3.5. Challenge 5: Multi-Domain Congestion Control ..............26
           3.5.1. Multi-Domain Transport of Explicit
                  Congestion Notification ............................26
           3.5.2. Multi-Domain Exchange of Topology or
                  Explicit Rate Information ..........................27
           3.5.3. Multi-Domain Pseudowires ...........................28
      3.6. Challenge 6: Precedence for Elastic Traffic ...............30
      3.7. Challenge 7: Misbehaving Senders and Receivers ............31
      3.8. Other Challenges ..........................................33
           3.8.1. RTT Estimation .....................................33
           3.8.2. Malfunctioning Devices .............................35
           3.8.3. Dependence on RTT ..................................36
           3.8.4. Congestion Control in Multi-Layered Networks .......36
           3.8.5. Multipath End-to-End Congestion Control and
                  Traffic Engineering ................................37
           3.8.6. ALGs and Middleboxes ...............................37