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Internet Engineering Task Force (IETF)                        C. Bastian
Request for Comments: 6057                                    T. Klieber
Category: Informational                                     J. Livingood
ISSN: 2070-1721                                                 J. Mills
                                                               R. Woundy
                                                                 Comcast
                                                           December 2010

        Comcast's Protocol-Agnostic Congestion Management System

Abstract

   This document describes the congestion management system of Comcast
   Cable, a large cable broadband Internet Service Provider (ISP) in the
   U.S.  Comcast completed deployment of this congestion management
   system on December 31, 2008.

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 Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are 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
   www.rfc-editor.org/info/rfc6057.

Copyright Notice

   Copyright (c) 2010 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
   (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.

Bastian, et al.               Informational                     [Page 1]
RFC 6057           An ISP Congestion Management System     December 2010

Table of Contents

   1. Introduction ....................................................2
   2. Applicability to Other Types of Networks ........................3
   3. Key Terminology .................................................3
   4. Historical Overview .............................................7
   5. Summary .........................................................8
   6. Relationship between Managing Congestion and Adding Capacity ....9
   7. Implementation and Configuration ...............................10
      7.1. Thresholds for Determining When a CMTS Port Is in a Near
           Congestion State ..........................................14
      7.2. Thresholds for Determining When a User Is in an
           Extended High Consumption State and for Release from
           That Classification .......................................15
      7.3. Effect of BE Quality of Service on Users'
           Broadband Experience ......................................19
      7.4. Equipment/Software Used and Location ......................21
   8. Conclusion .....................................................23
   9. Exceptional Network Utilization Considerations .................23
   10. Limitations of This Congestion Management System ..............24
   11. Low Extra Delay Background Transport and Other Possibilities ..24
   12. Security Considerations .......................................24
   13. Acknowledgements ..............................................25
   14. Informative References ........................................26

1.  Introduction

   Comcast Cable is a large broadband Internet Service Provider (ISP),
   based in the U.S., serving the majority of its customers via cable
   modem technology.  During the late part of 2008, and completing on
   December 31, 2008, Comcast deployed a new congestion management
   system across its entire network.  This new system was developed in
   response to dissatisfaction in the Internet community as well as
   complaints to the U.S. Federal Communications Commission (FCC)
   regarding Comcast's old system, which targeted specific peer-to-peer
   (P2P) applications.  This new congestion management system is
   protocol-agnostic, meaning that it does not examine or impact
   specific user applications or network protocols, which is perceived
   as a more fair system for managing network resources at limited times
   when congestion may occur.