76rd IETF - Hiroshima, Japan I. M. draft-wijnands-mpls-mldp-csc-02

MPLS WG This draft is submitted to the MPLS WG There is a small section that refers to L3VPN specific behavior. For that reason its presented in L3VPN today.

Problem statement mLDP LSP’s are build based on the Unicast reachability of the root address. Unicast routing decides how the LSP is build through the MPLS network. If the root address is not reachable in the core, the LSP can’t be established. This is possible when the root depends on a BGP route and the core is BGP free.

Problem statement (cont) The edge routers normally have the BGP route and know the exit point in the network that can be used to reach the root of the LSP.

Solution What if we can “temporarily” replace the FEC to reach the exit router, and restore the original FEC when the exit router is reached. We define a new mLDP Recursive Opaque encoding. The root of the ‘new’ FEC will be the IP address of exit router to reach the original root address. The ‘original’ FEC is encoded into the opaque field of the ‘new’ FEC.

mLDP Carriers Carrier P-PP-PE-1P-PE-2C-PE C-P ProviderCustomer C-rootP-root C-RootOpaqueP2MP Label Mapping C-FEC Customer sends a Label mapping to the Provider P-PE-1 router. P-PE-1 looks up the C-root into the routing table, result is P-PE-2 P-PE-1 copies C-FEC into P-FEC opaque encoding, P-PE-2 is the new root. Label mapping is transported through the provider network to P-PE-2 P-PE-2 is the P-root, recovers the C-FEC and sends a label mapping to customer based on the C-Root in the C-FEC. P-RootC-FECP2MP C-RootOpaqueP2MP Lookup C-root In Routing table

Global vs VRF The solution described in the previous slides works for mLDP LSPs created in the global context as well as in the VRF context. This feature in VRF context is used to support CsC for mLDP. The only difference is adding a RD to the recursive encoding.

Recursive Opaque Type | Type = 6 | Length | | | ~ | P2MP or MP2MP FEC Element | | | | Type = 7 | Length | | | | | Route Distinguisher (8 octets) | | | | ~ | P2MP or MP2MP FEC Element | | |

Route Distinguisher The RD is discovered dynamically via a unicast route lookup on the c-root address. BGP has the RD of the ingress PE that injected this route. This RD is used in the recursive encoding to make the FEC unique such that different Customers don’t have FEC collisions in the provider core.

L3VPN specific portion The L3VPN specific portion of the draft is very small. The draft is very small by it self. The authors like to keep this one draft and do the work in MPLS WG. We can issue a last-call in both MPLS and L3VPN.

Input from L3VPN MPLS WG The authors requested input from the MPLS and L3VPN WG. MPLS WG chairs are in support. 3 positive votes on the list. 1 negative vote on the list.

Questions?