Generic Connection Admission Control (GCAC) Algorithm Specification for IP/MPLS Networks
RFC 6601

Document Type RFC - Experimental (April 2012; No errata)
Was draft-ash-gcac-algorithm-spec (individual in rtg area)
Last updated 2013-02-12
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Internet Engineering Task Force (IETF)                       G. Ash, Ed.
Request for Comments: 6601                                          AT&T
Category: Experimental                                        D. McDysan
ISSN: 2070-1721                                                  Verizon
                                                              April 2012

  Generic Connection Admission Control (GCAC) Algorithm Specification
                          for IP/MPLS Networks


   This document presents a generic connection admission control (GCAC)
   reference model and algorithm for IP-/MPLS-based networks.  Service
   provider (SP) IP/MPLS networks need an MPLS GCAC mechanism, as one
   motivational example, to reject Voice over IP (VoIP) calls when
   additional calls would adversely affect calls already in progress.
   Without MPLS GCAC, connections on congested links will suffer
   degraded quality.  The MPLS GCAC algorithm can be optionally
   implemented in vendor equipment and deployed by service providers.
   MPLS GCAC interoperates between vendor equipment and across multiple
   service provider domains.  The MPLS GCAC algorithm uses available
   standard mechanisms for MPLS-based networks, such as RSVP, Diffserv-
   aware MPLS Traffic Engineering (DS-TE), Path Computation Element
   (PCE), Next Steps in Signaling (NSIS), Diffserv, and OSPF.  The MPLS
   GCAC algorithm does not include aspects of CAC that might be
   considered vendor proprietary implementations, such as detailed path
   selection mechanisms.  MPLS GCAC functions are implemented in a
   distributed manner to deliver the objective Quality of Service (QoS)
   for specified QoS constraints.  The objective is that the source is
   able to compute a source route with high likelihood that via-elements
   along the selected path will in fact admit the request.  In some
   cases (e.g., multiple Autonomous Systems (ASes)), this objective
   cannot always be met, but this document summarizes methods that
   partially meet this objective.  MPLS GCAC is applicable to any
   service or flow that must meet an objective QoS (delay, jitter,
   packet loss rate) for a specified quantity of traffic.

Ash & McDysan                 Experimental                      [Page 1]
RFC 6601           GCAC Algorithm for IP/MPLS Networks        April 2012

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and

   This document defines an Experimental Protocol for the Internet
   community.  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

Copyright Notice

   Copyright (c) 2012 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
   ( 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
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   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Ash & McDysan                 Experimental                      [Page 2]
RFC 6601           GCAC Algorithm for IP/MPLS Networks        April 2012

Table of Contents

   1. Introduction ....................................................4
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