1. Leaf discovery mechanism for mLDP based P2MP/MP2MP LSP
draft-jin-mpls-mldp-leaf-discovery-00
Lizhong Jin, ZTE
Kebo Liu, Nokia Siemens Networks

2. Problem statement (I) Problem statement
LDP for P2MP/MP2MP LSP, draft-ietf-mpls-ldp-p2mp-05.
There is management limitation for mLDP, because none of the members belong to P2MP LSP topology does not know all the members of the P2MP LSP.

3. Problem statement (II)
Multicast in VPLS, draft-ietf-l2vpn-vpls-mcast-05.
Root node will only know the mLDP P2MP LSP leaf node information if the P2MP LSP is triggered by BGP A-D mechanism.
Root node does not know any of the leaf node information if mLDP based P2MP LSP is setup by other application, e.g, static configuration. Instead, it will set up a new mLDP based LSP with same root and leaf node triggered by BGP A-D.
Conclusion: Multicast VPLS can only aggregate to mLDP P2MP/MP2MP LSP which is triggered by its own BGP A-D mechanism.
Similar problem for draft-ietf-l3vpn-2547bis-mcast-09

4. Problem statement (III)
P2MP PW, draft-martini-pwe3-p2mp-pw.
Root node will only know the mLDP based P2MP LSP leaf node information if the P2MP LSP is triggered by LDP label mapping message .
Root node does not know any of the leaf node information if mLDP based P2MP LSP is setup by other application, e.g, static configuration. Instead, it will set up a new P2MP LSP with same root and leaf node triggered by LDP label mapping message.
Conclusion: P2MP PW can only multiplex to mLDP P2MP LSP which is triggered by LDP label mapping message.

5. Problem statement (IV)
The mLDP based P2MP/MP2MP LSP setup by various applications can not be shared for multiplexing/aggregation with each other.
The introduced general leaf discovery mechanism for mLDP based P2MP/MP2MP LSP will assist various applications to share one P2MP/MP2MP LSP for multiplexing/aggregation.

6. Solutions mLDP notification extension solution
The leaf information is reported by the leaf node one by one to the root, through notification or label mapping.
The CONS: The mLDP scalability is influenced.
By using P2MP LSP Ping/BFD
It is not possible for Ping, because it is an on-demand function.
Additional overload will be added to the network.
Leaf discovery is more of a signaling requirement, not suitable to be solved by data plane tools.
By using T-LDP
Impact the mLDP scalability as small as possible.
Each leaf node will report the leaf node information to root through T-LDP.
By using BGP A-D
PROS:
BGP A-D is now a wildly accepted membership discovery mechanism.
CONS:
But the router should support BGP which usually is not possible for access/aggregate router.

7. T-LDP solution (I) Root P1 P2 P3 P4 P5 Notification Msg
P1 is the root of mLDP based P2MP LSP with FEC <X, Y>
Root P1
Notification Msg P2
Notification Msg
Withdraw Msg
Mapping Msg P3 P4 P5
P3 is adding to mLDP based P2MP LSP with FEC <X, Y>
P5 is leaving from mLDP based P2MP LSP with FEC <X, Y>

8. T-LDP solution (II) Leaf node identifier encoding
A leaf node identifier will uniquely identify a leaf node in the MPLS network.
Leaf operation status TLV encoding

9. Next steps
Need comments from work group
Thank you

10. Appendix: P2MP PW Multiplexing on P2MP LSP
P1 can not do P2MP PW multiplexing here!!!
P1 has MLDP base P2MP FEC <X, Y>, but does not know the leaf P3, P4 and P5.
Root P1
P1 has the information of P2MP PW, the required leaf is P3, P4, P5.
mLDP P2MP LSP leaf is configured here!!! P2
The MLDP base P2MP FEC <X, Y> is statically configured on each leaf.
P2MP PW
MLDP based P2MP LSP P3 P4 P5