BGP route propagation between neighboring domains

1
BGP route propagation between neighboring domains

• Renata Teixeira
• Laboratoire LIP6 CNRS
• University Pierre et Marie Curie Paris 6
• with
• Steve Uhlig (Delft University of Technology)
• Christophe Diot (Thomson)

2
Propagation of routing changes
Lip6 down
DT
AS 2
iBGP
eBGP
AS 1
AS 3
LIP6
Which routing changes propagate between
domains? How long does it take? Which factors
determine propagation delay?
3
Why understand route propagation?

• Improve protocol convergence
• Which components have greater impact in
  convergence time?
• Root-cause analysis
• When did a routing change happen at the origin
  network?

4
Previous studies

• Detailed data from one AS
• Full routing information from one network
• BGP, intra-domain routing, router configs
• No propagation between ASes
• Few vantage points at multiple ASes
• Publicly-available BGP feeds
• RIPE, RouteViews
• Limited visibility and knowledge of networks

5
Our approach

• Full routing data from two neighbor ASes
• Abilene US research network
• GEANT European research network
• Correlate routing changes
• From Abilene to GEANT and vice-versa

6
Abilene and GEANT
Internet
NY
AM
GEANT
Abilene
WA
FR
7
Challenges

• Monitoring infrastructure and data semantics
  depends on the network
• Pre-process data
• A single event may cause multiple messages
• Group related routing messages in time (70 secs)
• Timing depends on network and router configs
• Examine router configurations and BGP

8
Measurement infrastructure
BGP mon
ATL
NY
AM
GEANT
Abilene
WA
BGP mon
FR
BGP mon
Abilene - Monitors act as clients of
operational router - Receive all BGP changes
GEANT - Monitor is a BGP peer - Only
receive routes learned externally
BGP mon
9
Measuring route propagation
ATL
Univ
AM
NY
GEANT
Abilene
WA
FR
BGP mon
t1, ATL withdrawal Univ
BGP mon
t2, AM withdrawal Univ
t3, FR withdrawal Univ
Propagation time t2 t1
10
Components of route propagation
ATL
Univ
AM
NY
1
2
GEANT
Abilene
WA
FR
3
BGP mon
BGP mon
1. ATL to NY and WA iBGP out delay and
propagation delay load to transfer all routes
2. NY to AM and WA to FR eBGP out delay
Route-flap damping (depends on the prefix)
3. AM or FR to BGP mon iBGP out delay and
propagation delay load to transfer all routes
11
Configuration of Abilene and GEANT

• Abilene
• iBGP/eBGP out delay0
• No route-flap damping
• Low load Few prefixes and BGP sessions
• GEANT
• iBGP out delay0
• eBGP out delay10s and 30s
• Route-flap damping
• High load Full BGP tables (180K prefixes)

12
Propagation of BGP updates
36 of route changes from Abilene to
GEANT propagate immediately
Other route changes depend on route-flap damping
13
Propagation of BGP updates
Most routing changes (over 60) depend on the
load to transfer multiple routes
out delay from GEANT to Abilene depends on the
peering point
14
Summary

• Methodology to correlate BGP changes from
  neighbor ASes
• Components of route propagation
• Router configuration
• Out delay, route-flap damping
• Network connectivity
• Prefixes per session and number of sessions