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The Accumulated IGP Metric Attribute for BGP (RFC7311) Disclosure Number: IPCOM000238211D
Original Publication Date: 2014-Aug-01
Included in the Prior Art Database: 2014-Aug-08
Document File: 30 page(s) / 33K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

P. Mohapatra: AUTHOR [+4]


There are many routing protocols that have been designed to run within a single administrative domain. These are known collectively as "Interior Gateway Protocols" (IGPs). Typically, each link is assigned a particular "metric" value. The path between two nodes can then be assigned a "distance", which is the sum of the metrics of all the links that belong to that path. An IGP selects the "shortest" (minimal distance) path between any two nodes, perhaps subject to the constraint that if the IGP provides multiple "areas", it may prefer the shortest path within an area to a path that traverses more than one area. Typically, the administration of the network has some routing policy that can be approximated by selecting shortest paths in this way.

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Internet Engineering Task Force (IETF)                      P. Mohapatra Request for Comments: 7311                              Sproute Networks Category: Standards Track                                    R. Fernando ISSN: 2070-1721                                                 E. Rosen                                                      Cisco Systems, Inc.                                                                J. Uttaro                                                                     AT&T                                                              August 2014

               The Accumulated IGP Metric Attribute for BGP


   Routing protocols that have been designed to run within a single

   administrative domain (IGPs) generally do so by assigning a metric to

   each link and then choosing, as the installed path between two nodes,

   the path for which the total distance (sum of the metric of each link

   along the path) is minimized.  BGP, designed to provide routing over

   a large number of independent administrative domains (autonomous

   systems), does not make its path-selection decisions through the use

   of a metric.  It is generally recognized that any attempt to do so

   would incur significant scalability problems as well as inter-

   administration coordination problems.  However, there are deployments

   in which a single administration runs several contiguous BGP

   networks.  In such cases, it can be desirable, within that single

   administrative domain, for BGP to select paths based on a metric,

   just as an IGP would do.  The purpose of this document is to provide

   a specification for doing so.

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

 Mohapatra, et al.            Standards Track                    [Page 1]
 RFC 7311              AIGP Metric Attribute for BGP          August 2014

 Copyright Notice

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