1. 04/12/2001ecs289k, spring 20011 ecs298k: BGP Routing Protocol (2) lecture #4 Dr. S. Felix Wu Computer Science Department University of California, Davis http://www.cs.ucdavis.edu/~wu/ wu@cs.ucdavis.edu

2. 04/12/2001ecs289k, spring 20012 BGP Routing and Policy AS2 BGP Routing Policy RPSL

3. 04/12/2001ecs289k, spring 20013 Aggregation Policy Objects aggr-bndry, aggr-mtd, export-comps, inject, holes route:128.8.0.0/15 origin:AS1 components: route:128.8.0.0/15 origin:AS1 components:protocol BGP4 {128.8.0.0/16^+} protocol OSPF {128.9.0.0/16^+} route:128.8.0.0/15 origin:AS1 components:{128.8.0.0/15^-} aggr-mtd:outbound AS-ANY export-comps:{128.8.8.0/24} route:128.8.0.0/15 origin:AS1 components:{128.8.0.0/15^-} aggr-mtd:outbound AS-ANY inject:upon HAVE-COMPONENTS {128.8.0.0/16, 128.9.0.0/16} holes:128.8.8.0/24

4. 04/12/2001ecs289k, spring 20014 I-BGP/E-BGP AB A B.A C B.B.A ??

5. 04/12/2001ecs289k, spring 20015 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

6. 04/12/2001ecs289k, spring 20016 Route Flap Dampening If “flap” too frequent, treat it as down….

7. 04/12/2001ecs289k, spring 20017 ISP Example ISP3 - AS3 ISP1 - AS1ISP2 - AS2 R1 Customer1 AS10 Customer2 AS20 Customer3 AS30 138.39/16 204.70/16 128.4/16132.151/16 206.1.5/24 Community attribute: 1:777 1:666

8. 04/12/2001ecs289k, spring 20018 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

9. N > 4? AS1673 AS237 AS5696 AS2497 AS1239 AS6453 AS701 AS2914 AS6461 AS5000 AS6113 AS1 2914 237 1 5696 237 1239 5696 237 2497 5696 237 701 6461 5696 237 6461 5696 237 237 5696 237 5000 237 6113 2914 237 1673 5696 237 6453 1239 5696 237

10. 04/12/2001ecs289k, spring 200110 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)

11. 04/12/2001ecs289k, spring 200111 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

12. 04/12/2001ecs289k, spring 200112 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:140.00 (min/max 120/142) Announce AS4 AS5 AS8 AS7 AS3 (27) Announce AS4 AS5AS9 AS8 AS7 AS3(86) Withdraw (140 seconds) 27% Other

13. BGP Convergence Times

14. End-to-End Impact Failover