Session Initiation Protocol (SIP) Rate Control
RFC 7415

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Internet Engineering Task Force (IETF)                           E. Noel
Request for Comments: 7415                                     AT&T Labs
Category: Standards Track                                    P. Williams
ISSN: 2070-1721                                     BT Innovate & Design
                                                           February 2015

             Session Initiation Protocol (SIP) Rate Control

Abstract

   The prevalent use of the Session Initiation Protocol (SIP) in Next
   Generation Networks necessitates that SIP networks provide adequate
   control mechanisms to maintain transaction throughput by preventing
   congestion collapse during traffic overloads.  A loss-based solution
   to remedy known vulnerabilities of the SIP 503 (Service Unavailable)
   overload control mechanism has already been proposed.  Using the same
   signaling, this document proposes a rate-based control scheme to
   complement the loss-based control scheme.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in 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/rfc7415.

Copyright Notice

   Copyright (c) 2015 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.

Noel & Williams              Standards Track                    [Page 1]
RFC 7415                    SIP Rate Control               February 2015

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Rate-Based Algorithm Scheme .....................................3
      3.1. Overview ...................................................3
      3.2. Via Header Field Parameters for Overload Control ...........4
      3.3. Client and Server Rate-Based Control Algorithm Selection ...4
      3.4. Server Operation ...........................................5
      3.5. Client Operation ...........................................6
           3.5.1. Default Algorithm ...................................6
           3.5.2. Priority Treatment ..................................9
           3.5.3. Optional Enhancement: Avoidance of Resonance .......10
   4. Example ........................................................12
   5. Syntax .........................................................13
   6. Security Considerations ........................................13
   7. IANA Considerations ............................................13
   8. References .....................................................14
      8.1. Normative References ......................................14
      8.2. Informative References ....................................14
   Acknowledgments ...................................................14
   Contributors ......................................................14
   Authors' Addresses ................................................15

1.  Introduction

   The use of SIP [RFC3261] in large-scale Next Generation Networks
   requires that SIP-based networks provide adequate control mechanisms
   for handling traffic growth.  In particular, SIP networks must be
   able to handle traffic overloads gracefully, maintaining transaction
   throughput by preventing congestion collapse.

   A promising SIP-based overload control solution has been proposed in
   [RFC7339].  That solution provides a communication scheme for
   overload control algorithms.  It also includes a default loss-based
   overload control algorithm that makes it possible for a set of
   clients to limit offered load towards an overloaded server.  However,
   such a loss control algorithm is sensitive to variations in load so
   that any increase in load would be directly reflected by the clients
   in the offered load presented to the overloaded servers.  More
   importantly, a loss-based control scheme cannot guarantee an upper
   bound on the load from the clients towards an overloaded server and