preventing the unnecessary propagation of bgp withdraws · v. van den schrieck - networking 2009...
TRANSCRIPT
![Page 1: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/1.jpg)
Networking 2009, May 13th
Preventing the unnecessary propagation
of BGP withdraws
V. Van den Schrieck, P. François, C. Pelsser, O.Bonaventurehttp://inl.info.ucl.ac.be
![Page 2: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/2.jpg)
V. Van den Schrieck - Networking 2009
Agenda
• Introduction
• Presentation and evaluation of iBGP-caused withdraws
• Preventing iBGP-caused withdraws
✓ Advertising more than one path in iBGP (IETF)
✓ Our proposal : Advertising the availability of alternate paths in iBGP
2
![Page 3: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/3.jpg)
V. Van den Schrieck - Networking 2009
Agenda
• Introduction
• Presentation and evaluation of iBGP-caused withdraws
• Preventing iBGP-caused withdraws
✓ Advertising more than one path in iBGP (IETF)
✓ Our proposal : Advertising the availability of alternate paths in iBGP
3
![Page 4: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/4.jpg)
V. Van den Schrieck - Networking 2009
BGP, the glue of the Internet
• Border Gateway Protocol - Interdomain routing protocol used in the Internet
• Exchange paths to destinations between Autonomous Systems (AS)
✓ Each router advertises its best path to its BGP peers
✓ Selection process : Several rules
• A path is described by the AS Path, i.e. the sequence of AS that leads to the path destination
4
![Page 5: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/5.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6
![Page 6: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/6.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6> P : local
![Page 7: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/7.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6
P : 1
P : 1
> P : local
![Page 8: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/8.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6> P : local
> P : 1
> P : 1
![Page 9: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/9.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6> P : local
P : 3 1 > P : 1
> P : 1
P : 2 1
![Page 10: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/10.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6> P : local
> P : 3 1> P : 1
> P : 1
> P : 2 1
![Page 11: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/11.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6> P : local
> P : 3 1> P : 1
> P : 1
> P : 2 1 P : 4 3 1
P : 5 2 1
P : 5 2 1
![Page 12: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/12.jpg)
V. Van den Schrieck - Networking 2009
BGP
5
P
AS1
AS3
AS4
AS2
AS5
AS6> P : local
> P : 3 1> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 3 1 P : 5 4 3 1
![Page 13: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/13.jpg)
V. Van den Schrieck - Networking 2009
iBGP vs eBGP
• An Autonomous System has several routers
• All routers of an AS need to learn the paths to all destination advertised to the AS
✓ BGP sessions between routers of the AS : iBGP
- Specific iBGP rule : Do not advertise an iBGP-received path on an iBGP session
- Exception : Route Reflectors
✓ BGP sessions between routers of different AS : eBGP
6
![Page 14: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/14.jpg)
V. Van den Schrieck - Networking 2009
iBGP vs eBGP
7
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
![Page 15: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/15.jpg)
V. Van den Schrieck - Networking 2009
Agenda
• Introduction
• Presentation and evaluation of iBGP-caused withdraws
• Preventing iBGP-caused withdraws
✓ Advertising more than one path in iBGP (IETF)
✓ Our proposal : Advertising the availability of alternate paths in iBGP
8
![Page 16: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/16.jpg)
V. Van den Schrieck - Networking 2009
BGP Churn
• Churn is one of today’s BGP issues
• Churn : High number of unnecessary BGP messages
✓ Unnecessary : Do not impact the final routing state
• Consequences :
✓ Load on router’s CPU
✓ Transient losses of reachability
9
![Page 17: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/17.jpg)
V. Van den Schrieck - Networking 2009
BGP Churn
10
http://bgpupdates.potaroo.net/instability/bgpupd.html
• Average daily number of BGP updates : 400.000
![Page 18: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/18.jpg)
V. Van den Schrieck - Networking 2009
Origin of BGP churn
• Path exploration during BGP convergence
• Flapping prefixes
• Bad iBGP propagation
✓ Routers without path diversity could send unnecessary BGP withdraws in case of failure
✓ Even tough alternate paths exist in the AS
11
![Page 19: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/19.jpg)
V. Van den Schrieck - Networking 2009
Bad iBGP propagation
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
2 paths
1 path
![Page 20: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/20.jpg)
V. Van den Schrieck - Networking 2009
Origins of bad iBGP propagation
• Only best path announced on iBGP sessions
• One path preferred over all others => alternate paths are never propagated
✓ Path quality (AS path length)
✓ BGP policies (Local preference)
• Complex iBGP organizations
✓ Paths hidden by Route Reflectors
13
![Page 21: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/21.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
![Page 22: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/22.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
> P : 1
![Page 23: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/23.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
W(P)
> P : 1
![Page 24: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/24.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1
> P : 1
![Page 25: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/25.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
W(P)
W(P)
> P : 2 1
> P : 1
![Page 26: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/26.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
W(P)
W(P)
> P : 2 1
> P : 1> P : 5 2 1
![Page 27: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/27.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1
> P : 1> P : 5 2 1
> P : 2 1 P : 4 3 1
![Page 28: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/28.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1
> P : 1> P : 5 2 1
> P : 2 1 P : 4 3 1 P : 2 1 > P : 4 3 1
![Page 29: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/29.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1
> P : 1> P : 5 2 1
> P : 2 1 P : 4 3 1 P : 2 1 > P : 4 3 1
P : 4 3 1
W(P)
![Page 30: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/30.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1
> P : 1> P : 5 2 1
> P : 2 1 P : 4 3 1 P : 2 1 > P : 4 3 1
P : 2 1> P : 4 3 1
> P : 3 1 P : 5 2 1
![Page 31: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/31.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1
> P : 1> P : 5 2 1
> P : 2 1 P : 4 3 1 P : 2 1 > P : 4 3 1
P : 2 1> P : 4 3 1
P : 5 4 3 1
> P : 3 1 P : 5 2 1
![Page 32: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/32.jpg)
V. Van den Schrieck - Networking 2009
Withdraw Propagation when alternate path exists
14
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1
> P : 1> P : 5 2 1
> P : 2 1 P : 4 3 1 P : 2 1 > P : 4 3 1
P : 2 1> P : 4 3 1
P : 5 4 3 1
> P : 5 4 3 1
> P : 3 1 P : 5 2 1
![Page 33: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/33.jpg)
V. Van den Schrieck - Networking 2009
Quantification of unnecessary iBGP-caused Withdraws
• RouteViews Dataset : BGP feeds of parallel sessions (2 sessions with the same AS)
• Withdraw defined as iBGP-caused if the destination is withdrawn on one session, but stay stable on the other during 30 seconds before and after
• Withdraw is unnecessary because an alternate path exists in the AS
AS X
RouteView Collector
W (D)
15
![Page 34: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/34.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2
![Page 35: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/35.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2
![Page 36: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/36.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2
![Page 37: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/37.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2 W(P)
W(P)
![Page 38: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/38.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2 W(P)
W(P)
Withdraw detected=> start timer
![Page 39: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/39.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2
Withdraw detected
P : 2> P : 3 4
![Page 40: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/40.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2
Withdraw detected
P : 2> P : 3 4
P : 1 3 4
P : 3 4
![Page 41: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/41.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2
Withdraw detected
P : 2> P : 3 4 P : 2
> P : 3 4
![Page 42: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/42.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2
Withdraw detected
P : 2> P : 3 4 P : 2
> P : 3 4
P : 1 3 4
![Page 43: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/43.jpg)
V. Van den Schrieck - Networking 2009
Detecting unnecessary iBGP-caused withdraws
16
RouteView Collector
R2R1
AS2
AS1
AS3
AS4
> P : 2 P : 3 4> P : 2> P : 2
Withdraw detected
P : 2> P : 3 4 P : 2
> P : 3 4
P : 1 3 4
Timer expiredNo withdraw from R2
MATCH
![Page 44: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/44.jpg)
V. Van den Schrieck - Networking 2009
Quantification of iBGP-caused withdraws on RouteViews sessions
17
0
5000
10000
15000
20000
25000
30000
35000
40000
01-10-2008
02-10-2008
03-10-2008
04-10-2008
05-10-2008
06-10-2008
07-10-2008
08-10-2008
09-10-2008
10-10-2008
11-10-2008
12-10-2008
13-10-2008
14-10-2008
Num
ber
of w
ithdra
ws
Days
![Page 45: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/45.jpg)
V. Van den Schrieck - Networking 2009
Agenda
• Introduction
• Presentation and evaluation of iBGP-caused withdraws
• Preventing iBGP-caused withdraws
✓ Advertising more than one path in iBGP (IETF)
✓ Our proposal : Advertising the availability of alternate paths in iBGP
18
![Page 46: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/46.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
19
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
![Page 47: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/47.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
19
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
P : 2 1P : 4 3 1
![Page 48: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/48.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
19
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1 P : 4 3 1
![Page 49: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/49.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
19
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1 P : 4 3 1
> P : 1
![Page 50: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/50.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
19
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1 P : 4 3 1
W(P)
> P : 1
![Page 51: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/51.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
19
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1 P : 4 3 1
P : 5 4 3 1
P : 2 1 > P : 4 3 1
W(P)
> P : 1
![Page 52: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/52.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
19
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1> P : 2 1 P : 4 3 1
P : 5 4 3 1
P : 2 1 > P : 4 3 1
W(P)
> P : 5 4 3 1
P : 2 1 > P : 4 3 1
> P : 1
![Page 53: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/53.jpg)
V. Van den Schrieck - Networking 2009
Advertising multiple paths in iBGP
• Very promising solution, but :
✓ Need to modify the BGP protocol to support advertisement of multiple paths for a prefix
✓ All the routers of an AS need to be upgraded accordingly
20
![Page 54: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/54.jpg)
V. Van den Schrieck - Networking 2009
Agenda
• Introduction
• Presentation and evaluation of iBGP-caused withdraws
• Preventing iBGP-caused withdraws
✓ Advertising more than one path in iBGP (IETF)
✓ Our proposal : Advertising the availability of alternate paths in iBGP
21
![Page 55: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/55.jpg)
V. Van den Schrieck - Networking 2009
How to prevent iBGP-caused withdraws? (2)
• Instead of advertising alternate paths, advertise the availability of alternate paths
• BGP Community attribute used to tag this information to the path : DIVERSITY_AVAILABLE
• Lighter solution than the previous one, can be incrementally deployed
✓ No modification to BGP protocol
✓ DIVERSITY_AVAILABLE BGP community is simply not considered by legacy routers
22
![Page 56: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/56.jpg)
V. Van den Schrieck - Networking 2009
Advertising the availability of alternate paths
• Principle :
✓ A router knowing an alternate path
- Tags the community DIVERSITY_AVAILABLE to the primary path
- Then, it re-advertises the primary path to all its iBGP peers
23
![Page 57: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/57.jpg)
V. Van den Schrieck - Networking 2009 24
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
Advertising the availability of alternate paths
![Page 58: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/58.jpg)
V. Van den Schrieck - Networking 2009 24
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1
P : 2 1 - DIV_AV
Advertising the availability of alternate paths
![Page 59: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/59.jpg)
V. Van den Schrieck - Networking 2009 24
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1 P : 5 2 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
P : 2 1 - DIV_AV
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
![Page 60: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/60.jpg)
V. Van den Schrieck - Networking 2009
Advertising the availability of alternate paths
25
• When the primary path fails :
• Routers without an alternate path check the community
✓ If present : Wait for the alternate path before sending withdraws on eBGP
✓ Otherwise : send the withdraw on eBGP sessions immediately
![Page 61: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/61.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 3 1 P : 5 2 1
![Page 62: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/62.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 3 1 P : 5 2 1
![Page 63: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/63.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
W(P)
> P : 1
> P : 3 1 P : 5 2 1
![Page 64: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/64.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
> P : 3 1 P : 5 2 1
![Page 65: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/65.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
No eBGP WithdrawWait alternate path
> P : 3 1 P : 5 2 1
![Page 66: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/66.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
W(P)No eBGP WithdrawWait alternate path
> P : 3 1 P : 5 2 1
![Page 67: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/67.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
P : 2 1 > P : 4 3 1
No eBGP WithdrawWait alternate path
> P : 3 1 P : 5 2 1
![Page 68: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/68.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
P : 2 1 > P : 4 3 1
P : 4 3 1
No eBGP WithdrawWait alternate path
> P : 3 1 P : 5 2 1
W(P)
![Page 69: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/69.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
P : 2 1 > P : 4 3 1
P : 4 3 1
P : 2 1 - DIV_AV> P : 4 3 1
No eBGP WithdrawWait alternate path
> P : 3 1 P : 5 2 1
W(P)> P : 3 1 P : 5 2 1
![Page 70: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/70.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
P : 2 1 > P : 4 3 1
P : 2 1 - DIV_AV> P : 4 3 1
P : 5 4 3 1
> P : 3 1 P : 5 2 1> P : 3 1 P : 5 2 1
![Page 71: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/71.jpg)
V. Van den Schrieck - Networking 2009 2619
12
AS1
AS3
AS4
AS2AS6
AS5R1
R2
eBGP sessioniBGP session
> P : local
> P : 3 1
> P : 1
> P : 1
> P : 2 1 P : 4 3 1
> P : 5 2 1
> P : 2 1 - DIV_AV
Advertising the availability of alternate paths
> P : 1
> P : 2 1 - DIV_AV
P : 2 1 > P : 4 3 1
P : 2 1 - DIV_AV> P : 4 3 1
P : 5 4 3 1
> P : 5 4 3 1
> P : 3 1 P : 5 2 1> P : 3 1 P : 5 2 1
![Page 72: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/72.jpg)
V. Van den Schrieck - Networking 2009
Policy-equivalent paths
• In practice : due to policies, alternate paths can still trigger eBGP withdraws
✓ Use two communities instead of one
27
![Page 73: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/73.jpg)
V. Van den Schrieck - Networking 2009
Conclusion
• We highlighted the contribution of iBGP-caused withdraws to BGP churn
• Two solutions to prevent this unnecessary withdraw propagation :
✓ Add-Paths (IETF)
✓ Our proposal : Diversity communities
• Work in progress : Evaluate the reduction of churn resulting from using our solution
✓ Simulations on generated Internet topologies
28
![Page 74: Preventing the unnecessary propagation of BGP withdraws · V. Van den Schrieck - Networking 2009 Quantification of unnecessary iBGP-caused Withdraws • RouteViews Dataset: BGP feeds](https://reader034.vdocuments.us/reader034/viewer/2022042312/5eda68e8b3745412b5714b22/html5/thumbnails/74.jpg)
V. Van den Schrieck - Networking 2009
Questions?
• More information on : http://inl.info.ucl.ac.be
29