1. Multicast LDP extension for hub & spoke multipoint LSP
MPLS IETF79
draft-jin-jounay-mpls-mldp-hsmp-01
Lizhong Jin, ZTE
Frederic Jounay, France Telecom
IJsbrand Wijnands, Cisco Systems
Nicolai Leymann, Deutsche Telekom

2. Introduction Definition:
hub & spoke multipoint LSP (short for HSMP LSP)
Allows traffic both from root to leaf through P2MP LSP and also leaf to root along the co-routed reverse path. P1
Root P2
Transit node
Leaf P3 P4 P5
Leaf
Leaf

3. Applications
Time synchronization based on [IEEE1588v2], requires sync and delay request message to follow the same path.
HSMP for phase/time delivery with TCKs.
HSMP for phase/time delivery with BCKs.
Accurate quantification of one-way delay for P2MP connection requires time synchronization :
HSMP LSP can be used to do time synchronization based on [IEEE1588v2] for P2MP connection.

4. Applications (cont) IPTV scenario
IGMP is used for signaling between senders and receivers, the messages from the receivers are travelling only from the leaves to the root (and from root towards leaves), but not from leaf to leaf.
Traffic from the root is only replicated towards the leaves.
Then leaf node receiving IGMP message (for SSM case) will join HSMP LSP, and send IGMP message upstream to root along HSMP LSP.
P2MP PW with reverse path can multiplex to HSMP LSP instead of one P2MP LSP + independent reverse path.
In that case, the operational cost will be reduced for maintaining only one HSMP LSP.

5. Setting up HSMP LSP The difference with MP2MP LSP:
The leaf LSRs can only send traffic to root node along the same path of traffic from root node to leaf node.
HSMP LSP consists of:
A downstream path
Same as P2MP downstream path in MP2MP LSP
A upstream path
Only from leaf to root node, without communication among leaf and leaf nodes;
Detail: HSMP LSP will allocate one label for all downstream node for the upstream path, while MP2MP LSP will allocate different labels for different downstream node.

6. HSMP LSP signaling Transit Node Root Leaf A LM [D<x,y>, L1]2
LM [U<x,y>, L2] 3
LM [D<x,y>, L3]
Leaf B 4
LM [U<x,y>, L4] 5
LM [D<x,y>, L5] 6
LM [U<x,y>, L2]
Note: LM [D<x,y>, L1]: Label Mapping with FEC(D<x,y>) and label(L1)

7. Next steps
Need comments from work group
Thank you