Network Working Group J. Uttaro
Internet Draft AT&T
Intended status: Standards Track V. Van den Schrieck
Nov 26, 2012 Individual Contributor
Expires: May 26, 2013 P. Francois
IMDEA Networks
R. Fragassi
A. Simpson
Alcatel-Lucent
P. Mohapatra
Cisco Systems
Best Practices for Advertisement of Multiple Paths in IBGP
draft-ietf-idr-add-paths-guidelines-04.txt
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Abstract
Add-Paths is a BGP enhancement that allows a BGP router to advertise
multiple distinct paths for the same prefix/NLRI. This provides a
number of potential benefits, including reduced routing churn, faster
convergence and better loadsharing.
This document provides recommendations to implementers of Add-Paths
so that network operators have the tools needed to address their
specific applications and to manage the scalability impact of Add-
Paths. A router implementing Add-Paths may learn many paths for a
prefix and must decide which of these to advertise to peers. This
document analyses different algorithms for making this selection and
provides recommendations based on the target application.
Table of Contents
1. Introduction...................................................4
2. Terminology....................................................4
3. Add-Paths Applications.........................................5
3.1. Fast Connectivity Restoration.............................5
3.2. Load Balancing............................................7
3.3. Churn Reduction...........................................7
3.4. Suppression of MED-Related Persistent Route Oscillation...7
4. Implementation Guidelines......................................8
4.1. Capability Negotiation....................................8
4.2. Receiving Multiple Paths..................................9
4.3. Advertising Multiple Paths................................9
4.3.1. Path Selection Modes................................11
4.3.1.1. Advertise All Paths............................11
4.3.1.2. Advertise N Paths..............................12
4.3.1.3. Advertise All AS-Wide Best Paths...............12
4.3.1.4. Advertise ALL AS-Wide Best and Next-Best Paths
(Double AS Wide)........................................13
4.3.2. Derived Modes from Bounding the Number of Advertised
Paths......................................................14
5. Deployment Considerations.....................................14
5.1. Introducing Add-Paths into an Existing Network...........14
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