The Accumulated IGP Metric Attribute for BGP (RFC7311)
Original Publication Date: 2014-Aug-01
Included in the Prior Art Database: 2014-Aug-08
Internet Society Requests For Comment (RFCs)
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.
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 http://www.rfc-editor.org/info/rfc7311.
Mohapatra, et al. Standards Track [Page 1]
RFC 7311 AIGP Metric Attribute for BGP August 2014
Copyright (c) 2014 IETF Trust and the persons identified as the ...