LDP IGP Synchronization

1
LDP IGP Synchronization

• draft-jork-ldp-igp-sync-00
• Markus Jork ltmjork_at_avici.comgt
• Alia Atlas ltaatlas_at_avici.comgt
• Luyuan Fang ltluyuanfang_at_att.comgt

2
The Problem
A
LDP session
shortest path
C
B

• inoperational LDP session along shortest IGP path
  causes blackhole
• serious problem for traffic depending on MPLS
  forwarding that cannot be routed (L3VPN,
  pseudowire)
• can be persistent or transient error condition
• occurs also as part of normal operation when link
  comes up

3
The Solution
10
10
A
10
10
10
65535
C
B

• raise IGP cost on link with inoperational LDP
  session
• this causes LDP traffic to go over valid path but
  also forces IP traffic over non-optimal path
• approach is similar to RFC 3137
• no protocol change

4
Feedback Received So Far

• describe interaction with TE tunnels
• not changing TE link cost prevents tunnel reroute
• feature can also be applied to targeted LDP
  sessions over TE tunnels where no IGP adjacency
  exists