P2MP MPLS-TE FRR with P2MP Bypass Tunnel draft-leroux-mpls-p2mp-te-bypass-00.txt

J.L. Le Roux (France Telecom) R. Aggarwal (Juniper)

IETF 67, MPLS WG, San Diego 11/08/2006

Background 1/2

Extensions to detour and facility backup FRR procedures so as to support FRR protection of P2MP TE-LSPs defined in draft-ietf-mpls-p2mp-rsvp-te-p2mp

Facility backup protection only relies on P2P Bypass tunnels

Hence to protect a branch node, several P2P Bypass tunnels are required and the PLR must replicate the traffic

This may lead to significant inefficient bandwidth usage

Background 2/2

Traffic replicated on shared linksIn some networks there may be several tens of LSRs downstream to

a protected node on a P2MP LSPOperational exemples with 30 downstream LSRs…

This may make this solution inapplicable

R1

R2

R5

R4

R3

Protected P2MP TE-LSP

P2P Bypass tunnel

40 -> 45, R4 22, R5

25 -> 40, R2 FRR -> 30, 45, R3 31, 22, R2

30-> pop, R4 31->pop, R5

IP25

IP45

IP22

IP28

IP37

IP40

IP4530

45-> 28, R6

22-> 37, R7

IP2231

IP45

IP22

Replication

Solution overview

This draft defines extensions to the facility backup FRR procedure so as to support P2MP Bypass tunnels

A P2MP Bypass Tunnel is used to protected a set of P2MP TE-LSPs against branch node failure

A set of P2MP LSPs that traverse the PLR, the protected node and the set of MPs can be protected by the same P2MP Bypass Tunnel

During failure the traffic on a protected P2MP TE-LSP is tunneled within a P2MP bypass tunnel towards the set of MPs thanks to label stacking

Inner label = backup LSP Label, used on the MP to forward traffic to the protected LSP. Outer label = P2MP Bypass tunnel Label

To avoid data replication on the PLR, a same backup LSP label (inner label) is assigned by the PLR to all MPs, following RSVP-TE Upstream Label Assignment procedure (= P2MP MPLS Hierarchy)

draft-ietf-mpls-rsvp-upstream-00.txt

PLR Procedure

To protect a P2MP TE-LSP against branch node failure the PLR selects an appropriate P2MP bypass tunnel

The set of Bypass Leaf LSRs (MP) must allow reaching all leaves downstream to the protected node

The backup P2MP LSP is signaled prior to the failure The same backup LSP label is assigned by the PLR to all MPs, in the context

of the P2MP Bypass Tunnel For each MP, the PLR sends one or more Path messages including:

One or more S2L sub-LSPs that transit through the MPAn Upstream Assigned Label Object carrying the backup LSP label (inner label)The Bypass Tunnel session object carried within the IF-ID HOP object

–This allows context identification on the MP

Path messages for the backup LSP sent using directed signaling During failure the PLR reroutes the traffic received on a P2MP TE-LSP within

the P2MP Bypass tunnel, with the corresponding backup LSP label

MP Procedure

A backup LSP label is looked up in the context of the underlying P2MP bypass tunnel on which the packet is received

This requires PHP to be deactivated on the P2MP bypass tunnel

The MP maintains a context specific ILM per P2MP bypass tunnelThe MP installs the backup LSP label in the ILM for the

corresponding P2MP bypass tunnelIdentified by its session object carried in the IF-ID HOP object

A backup LSP label is mapped to the outgoing interface(s) and label(s) of the corresponding protected P2MP LSP

Illustration

R1

R2

R5

R4

R3

Protected P2MP TE-LSP

P2MP Bypass tunnel

IP25

IP22

IP28

IP37

IP40

IP5030IP45

R6

R7

P2MP tunnel B

P2MP tunnel P

Path P2MP tunnel Psender R1sub-lsp to R6UA Label 50IF HOP = tunnel B

Path P2MP tunnel Psender R1sub-lsp to R7UA Label 50IF HOP = tunnel B

40 -> 45, R4 22, R5

25 -> 40, R2 FRR: 50, 30, R3

30-> 21, R4 23, R5

45-> 28, R6 21 -> P2MP Tunnel B ILM

22-> 37, R7 23 -> P2MP Tunnel B ILM

P2MP tunnel B ILM (label 21) 50 -> 28, R6

P2MP tunnel B ILM (label 23) 50 -> 37, R7

IP5021

IP5023

Next StepsNeed to address comments received on the list and offlineA P2MP LSP could be protected using a combination of P2MP

bypass tunnelsUseful when there is no overlapping Bypass, Allows reusing existing BypassReduces the number of bypass, but requires replication

–Tension between control plane optimization and data plane optimization

Need to discuss backward compatibility with MP that do not support upstream label assignment: Combination of P2MP and P2P Bypass

Support for P2MP bypass whose leaf LSRs are a superset of the protected LSP downstream LSRs

Aggregation that allows significant reduction of the number of bypass LSPsCounter part: During failure, the traffic is sent to LSRs that are not MP of the

protected LSP (they will drop the traffic), again the tension

Define procedures for LAN interface protectionA P2MP Bypass can be used to protect a LAN interface that connects a

branch LSR and a set of downstream LSRs

Conclusion

This drafts complements the base P2MP RSVP-TE spec

WG feedback is required

Adopt as WG doc?

Thanks

Questions?