1. P2MP MPLS-TE Fast Reroute with P2MP Bypass Tunnels
P2MP MPLS-TE Fast Reroute with P2MP Bypass Tunnels draft-ietf-mpls-p2mp-te-bypass-01.txt J.L. Le Roux (France Telecom) R. Aggarwal (Juniper) J.P. Vasseur (Cisco Systems) M. Vigoureux (Alcatel-Lucent)
IETF 69, MPLS WG, Chicago

2. Document Overview
Limitations of P2P bypass tunnels to protect a P2MP LSP => Traffic duplication…
To overcome these limitations this draft defines extensions to the FRR procedures to support P2MP Bypass tunnels
Retain scalability advantages of MPLS label stacking
Avoids sending multiple copies of a packet on some links during failure
During failure the traffic is tunneled within one or more P2MP bypass towards the set of Merge Points 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 inner label is assigned by the PLR to all MPs on a given P2MP bypass
following RSVP-TE Upstream Label Assignment procedure
draft-ietf-mpls-rsvp-upstream

3. Changes since last version
Draft adopted as WG document in May
No PHP on the bypass tunnel to allow for context identification
Bypass signaled with the No-PHP desired bit, as specified in draft-ali-mpls-rsvp-te-no-php-oob-mapping
Reversion: Entirely rely on procedures defined in RFC4090
global and local revertive modes
Clarifications on PLR location: local or remote
Combination of P2P and P2MP Bypass tunnels for backward comp
Bypass tunnel selection options clarified
Link protection procedures clarified
Procedures for Partial protection
Some rewordings for the sake of clarity

4. Combination of P2P and P2MP Bypass
No Up Label capable
P2P Bypass
P2MP bypass and P2P bypass can be used in conjunction
For MP on P2P bypass => follow procedures in 4875
For MP on P2MP Bypass => follow procedures in this doc
No upstream label assignment for MP leaves of P2P bypass
Allows for backward compatibility with MP that do not support upstream label assignment
P2MP Bypass

5. P2MP Bypass Tunnel selection options
Various options to protect a P2MP LSP with P2MP bypass
1: A single P2MP Bypass tunnel whose leaves exactly match the set of MPs
2: A single P2MP Bypass tunnel whose leaves are a superset of the set of MPs
Leaves that are not MP drop the traffic
3: Several P2MP bypass tunnels whose combined leaves cover all MPs
These options differ in terms of bandwidth consumption and number of P2MP bypass to be maintained
P2MP Hierarchy => Tension between control plane and data plane optimization
The choice depends on the desired state/bandwidth tradeoff, and the operational complexity

6. Link protection with P2P Bypass
Default procedure (defined in RFC4875)
May lead to traffic duplication on some links during failure
When the bypass follows another downstream link on the P2MP LSP
Protected P2MP TE-LSP
P2P Bypass tunnel
Duplication R3 R1 R2

7. Link Protection with P2MP Bypass
No Duplication R3
Protected P2MP TE-LSP
P2MP Bypass tunnel R1 R2
OPTIONAL procedure: A link MAY be protected by A P2MP bypass that tunnels traffic towards MPs downstream to the PLR
Some MPs are downstream to the PLR but not downstream to the failed element (not impacted by the failure)
The PLR must stop sending traffic to these MP within the protected P2MP LSP
Allows avoiding sending twice the traffic on a downstream link

8. P2MP Partial Protection
Uncovered MP
P2MP Primary
Partial prot allowed
In some cases the PLR may not be able to find a set of P2P and/or P2MP Bypass Tunnels that cover all merge points
"P2MP Partial Protection": Only a subset of MP are covered
upon failure, traffic will not be delivered to all leaf LSRs
Default PLR behavior: Full protection if feasible else no protection
The Ingress LSR may request for "P2MP Partial Protection", such that if a P2MP LSP cannot be fully protected it is partially protected
P2MP Bypass

9. Next Steps
Need to align with the mpls-upstream draft => The PLR assigns upstream labels from a single label space
WG feedback required
A new revision to be submitted before Vancouver meeting
figures, examples, clarifications

10. Thanks Questions?

11. Appendix

12. Limitations of the P2P Bypass approach node protection
Using P2P bypass tunnels for P2MP LSP node protection leads to traffic duplication on some links during failure
Protected P2MP TE-LSP R3
P2P Bypass tunnel
Duplication R4 R2 R1 R5

13. Link protection with P2P Bypass
Default procedure (defined in RFC4875)
May lead to traffic duplication on some links during failure
When the bypass follows another downstream link on the P2MP LSP
Protected P2MP TE-LSP
P2P Bypass tunnel
Duplication R3 R1 R2

14. Protection with P2MP Bypass
Protected P2MP TE-LSP
P2MP Bypass tunnel
Path P2MP tunnel P
sender R1
sub-lsp to R6
UA Label 50
IF-ID = 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 R3 IP 50 21 IP 28 R4 R6
P2MP tunnel B IP 50 30 IP 45
P2MP tunnel P IP 50 23
P2MP tunnel B ILM (label 21)
50 -> 28, R6 IP 25 R2 R1 IP 40
Path P2MP tunnel P
sender R1
sub-lsp to R7
UA Label 50
IF-ID = tunnel B IP 22 R5 R7 IP 37
P2MP tunnel B ILM (label 23)
50 -> 37, R7

15. P2MP Bypass Tunnel Selection Option 1
Protected P2MP TE-LSP
P2MP Bypass tunnel

16. P2MP Bypass Tunnel Selection Option 2
Protected P2MP TE-LSP
P2MP Bypass tunnel
drop R6

17. P2MP Bypass Tunnel Selection Option 3
Protected P2MP TE-LSP
P2MP Bypass tunnel