02024 aspath 2 2 2 2 2 2 2 2 2 2 2 2 2 2 primary

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Unformatted text preview: ath- vector protocol •  Policy- based rou9ng based on AS Paths •  Evolved during the past 20+ years •  1989 : BGP-1 [RFC 1105], replacement for EGP •  1990 : BGP-2 [RFC 1163] •  1991 : BGP-3 [RFC 1267] •  1995 : BGP-4 [RFC 1771], support for CIDR •  2006 : BGP-4 [RFC 4271], update BGP Opera9ons Establish session on TCP port 179 AS1 BGP session Exchange all active routes Exchange incremental updates AS2 While connection is ALIVE exchange route UPDATE messages 33 10/29/13 Incremental Protocol •  A node learns mul9ple paths to des9na9on –  Stores all of the routes in a rou9ng table –  Applies policy to select a single ac9ve route –  … and may adver9se the route to its neighbors •  Incremental updates –  Announcement •  Upon selec9ng a new ac9ve route, add node id to path •  … and (op9onally) adver9se to each neighbor –  Withdrawal •  If the ac9ve route is no longer available •  … send a withdrawal message to the neighbors ASPATH Alribute 128.112.0.0/16 AS Path = 1755 1239 7018 88 128.112.0.0/16 AS Path = 1239 7018 88 AS 1239 Sprint AS 1755 AS 88...
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This document was uploaded on 04/04/2014.

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