04/12/2001ecs289k, spring ecs298k: BGP Routing Protocol (2) lecture #4 Dr. S. Felix Wu Computer Science Department University of California, Davis

04/12/2001ecs289k, spring BGP Routing and Policy AS2 BGP Routing Policy RPSL

04/12/2001ecs289k, spring Aggregation Policy Objects aggr-bndry, aggr-mtd, export-comps, inject, holes route: /15 origin:AS1 components: route: /15 origin:AS1 components:protocol BGP4 { /16^+} protocol OSPF { /16^+} route: /15 origin:AS1 components:{ /15^-} aggr-mtd:outbound AS-ANY export-comps:{ /24} route: /15 origin:AS1 components:{ /15^-} aggr-mtd:outbound AS-ANY inject:upon HAVE-COMPONENTS { /16, /16} holes: /24

04/12/2001ecs289k, spring I-BGP/E-BGP AB A B.A C B.B.A ??

04/12/2001ecs289k, spring How to prevent loop in... E-BGP: –examine the AS Path. –As long as we do not find the same AS# twice I-BGP: –prefix learned from an I-BGP neighbor can NOT be advertized to another I-BGP neighbor. –Full mesh

04/12/2001ecs289k, spring Route Flap Dampening If “flap” too frequent, treat it as down….

04/12/2001ecs289k, spring ISP Example ISP3 - AS3 ISP1 - AS1ISP2 - AS2 R1 Customer1 AS10 Customer2 AS20 Customer3 AS / / / / /24 Community attribute: 1:777 1:666

04/12/2001ecs289k, spring BGP Convergence Example R AS0 AS1 AS2 AS3 *B Rvia 3 B R via 03 B R via 23 *B Rvia 3 B R via 03 B R via 13 *B Rvia 3 B R via 13 B R via 23 AS0AS1AS2

N > 4? AS1673 AS237 AS5696 AS2497 AS1239 AS6453 AS701 AS2914 AS6461 AS5000 AS6113 AS

04/12/2001ecs289k, spring ISP1-ISP4 Paths During Failure Only one back up path (length 3) Steady State ISP 1 ISP 5 P2 ISP 4 R1R1 FAULT 96%Average: 92 (min/max 63/140) seconds Announce AS4 AS5 AS1 (44 seconds) Withdraw(92 seconds) 4%Average: 32 (min/max 27/38) seconds Withdraw(32 seconds)

04/12/2001ecs289k, spring ISP2-ISP4 Paths During Failure Steady State ISP 2 ISP 4 P2 ISP 5 P3 ISP 6 R2R2 FAULT Vagabond P4 ISP 10 ISP 11 ISP 12 ISP 13 P4 63% Average: 79 (min/max 44/208) seconds AS4 AS5 AS2(35 seconds) Withdraw (79 seconds) 7% Average: 88 (min/max 80/94) seconds Announce AS4 AS5 AS2 (33 seconds) Announce AS4 AS6 AS5 AS2 (61 seconds) Withdraw (88 seconds) 7% Average: 54 (min/max 29/9) seconds Withdraw (54 seconds) 23% Other

04/12/2001ecs289k, spring ISP3-ISP4 Paths During Failure ISP 3 Steady State ISP 4 R3R3 P2 ISP 5 FAULT ISP 1 P3 P6 P7 P4 P5 P6 ISP 7 ISP 9 ISP 8 P7 P4 36% Average: 110 (min/max 78/135) seconds Announce AS4 AS5 AS (52 seconds) Withdraw (110 seconds) 35% Average: 107 (min/max 91/133) seconds Announce AS4 AS1 AS3 (39 seconds) Announce AS4 AS5 AS3 (68 seconds) Withdraw (107 seconds) 2% Average: (min/max 120/142) Announce AS4 AS5 AS8 AS7 AS3 (27) Announce AS4 AS5AS9 AS8 AS7 AS3(86) Withdraw (140 seconds) 27% Other

BGP Convergence Times

End-to-End Impact Failover