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Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with...
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![Page 1: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/1.jpg)
Modeling Inter-Domain Routing
Protocol Dynamics
ISMA 2000December 6, 2000
In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary, Madan Musuvathi
Craig LabovitzMerit Network/Microsoft Research
![Page 2: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/2.jpg)
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Routing Dynamics
Goal: Develop a model of Internet inter-domain routing protocol dynamics. Easy, right?
Subgoals– Model impact of failures and topological changes on end-to-end
paths– Predict/measure reliability of inter-AS links, routers, etc.– Compare steady-state topology compare to topologies under
failure– Figure out where all of those darn BGP updates come from
![Page 3: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/3.jpg)
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Stuff
• Old stuff– Measurements of BGP updates and convergence
– Model BGP convergence (upper and lower bounds)
• New Stuff– Protocol timer trade-offs
– Improvements to BGP (BGP-CT)
![Page 4: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/4.jpg)
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Data Sets & Tools
• Default-free BGP peering sessions– (routeviews.merit.edu, 2 Equinix probes, 1 Mae-West,
several iBGP probes, Merit RSNG route servers)– Daily tables and all BGP updates/events sent to RS
over last five years– Daily default-free dumps (and all updates/events) for
20-30 peers for last two years• Fault injection probes (OSPF/BGP)• Analysis/Tools
– MRT/Perl (playing with SSFNet)– RouteTracker (whois.routetracker.net)
![Page 5: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/5.jpg)
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Internet BGP Update Volume
• Withdraws in millions until 2/1998 due to withdraw looping/Cisco bug. Dramatic drop after IOS release
Announcements growing after 6/98 due to MED policy and convergence?
![Page 6: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/6.jpg)
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MTTF of Backbone Networks
• Informally: How long before a network is unreachable?
• Majority of Internet routes unreachable within 30 days
![Page 7: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/7.jpg)
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Mean Time to Fail-Over
• How long before traffic is re-routed?
• Majority of Internet routes which possess backup paths fail-over every 3 days
![Page 8: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/8.jpg)
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Internet Route Repair
• How long before a network is reachable again?
• Long-tailed distribution with plateau at 30 minutes. Why this plateau?
![Page 9: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/9.jpg)
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BGP Convergence
• If complete graph, N! upper theoretic bound and 30*(N-3) lower bound
• In practice, Internet has hierarchy and customer/provider/sibling relationships. Bounded by length longest possible path
![Page 10: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/10.jpg)
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BGP Convergence ExampleR
AS0 AS1
AS2AS3
*B R via 3 B R via 03 B R via 23
*B R via 3 B R via 03 B R via 13
*B R via 3 B R via 13 B R via 23
AS0 AS1 AS2
** **B R via 203
*B R via 013 B R via 103
![Page 11: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/11.jpg)
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Observed Fault Injection Topologies
• In steady-state, topologies between ISP1, ISP2, ISP3 similar – all direct BGP peers of ISP4.
• Repeatedly withdrew single-homed route (R1, R2, R3)
Steady State
ISP 1R1
Withdraw
ISP 4
ISP 2R2
Withdraw
Steady State
ISP 3R3
Withdraw
Steady State
MAE-WEST
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Comparing ISP Convergence Latencies
• CDF of faults injected into three Mae-West providers and observed at ISP router in Japan• Significant variations between providers
![Page 13: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/13.jpg)
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ISP1-ISP4 Paths During Failure
• Only one back up path (length 3)
Steady State
ISP 1
ISP 5
P2
P2ISP 4
R1
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)
![Page 14: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/14.jpg)
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ISP2-ISP4 Paths During Failure
Ste
ady
Sta
te
ISP 2
ISP 4
P2
P2
ISP 5
P3
P3
P3
ISP 6
R2
FAULT
Vagabond
P4
P4ISP 10
ISP 11
ISP 12
ISP 13
P4
P4
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
![Page 15: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/15.jpg)
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ISP3-ISP4 Paths During Failure
ISP 3
Ste
ady
St a
t e
ISP 4
R3
P2
P2
ISP 5
FAULT
ISP 1
P3
P3
P6
P7
P7P4
P4
P5
P5
P5P5
P5
P6
P6
P6
ISP 7
ISP 9
ISP 8
P7
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
![Page 16: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/16.jpg)
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Race Conditions and Paths
• T(shortest path) <= Tdown <= T(longest path)
B
A
![Page 17: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/17.jpg)
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Relationship Between Backup Paths and Convergence
• Convergence related to length of longest possible backup ASPath between two nodes
Longest Observed ASPath Between AS Pair
![Page 18: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/18.jpg)
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Towards Fast BGP Convergence
Four possible solutions
• No transit/One-hop topology (peer and filter everyone)
• Turn off/Change MinRouteAdver timer
• “Tag” BGP updates and provide hint so nodes can detect bogus state information
• Entirely new protocol
![Page 19: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/19.jpg)
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255 AS Topology0
10
20
30
40
50
60
70
80
90
100
0 50 100 150 200 250 300 350 400 450
Seconds
Cumulative Percentage
MRA, CT
MRA, No CT
No MRA, No CT
![Page 20: Modeling Inter-Domain Routing Protocol Dynamics ISMA 2000 December 6, 2000 In collaboration with Abha, Ahuja, Roger Wattenhofer, Srinivasan Venkatachary,](https://reader033.fdocuments.in/reader033/viewer/2022052509/56649c765503460f9492aa6b/html5/thumbnails/20.jpg)
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255 AS Topology0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 100012001400 16001800
Number of Messages
Cumulative Percentage
MRA, CT
MRA, No CT
No MRA, No CT
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BGP-CT
• Incremental addition to BGP4– Capability negotiation– Tags carried in as multi-protocol NRLI extension– Invalidate alternative paths if match tag (and other necessary
conditions met)
• Details– New state machine additions (temporary invalidation)– Works with iBGP– Implemented MRT and deployed on CAIRN– Improves BGP convergence by an order of magnitude in most
cases (in a few cases, behavior is worse)