1. Multi-domain MPLS Deployment Enhancement
draft-xu-mpls-multi-domain-deployment-enhancement-00
Xiaohu Xu (Huawei)
Zhenbin Li (Huawei)
IETF88, Vancouver

2. Inter-area LSP (labeled BGP) Intra-area LSP (LDP/RSVP-TE)
Current Deployment
PE-2
PE-7(R7)
Area 0
Area 1
Area 2
PE-1
ABR-22 (RR)
ABR-12 (RR)
Service Layer
Inner Transport Layer
Outer Transport Layer
VPN Label or PW Label
Inter-area LSP (labeled BGP)
Intra-area LSP (LDP/RSVP-TE)
IBGP
VPN or PW Signaling
ABR-11 (RR)
ABR-21 (RR)
P (RR)
Potential challenges:
Labeled BGP routes for PE routers are non-aggregatable and therefore it would cause BGP RIB and even MPLS forwarding table scalability concerns, especially in large-scale networks (e.g., in seamless MPLS target scenario, there would be 100,000 access nodes which act as PE routers)
BGP filter could limit the propagation of the labeled routes but this approach is heavy-duty and less effective for some nodes where a lot of inter-domain LSPs pass through.
Egress BGP node protection mechanism is complex due to labeled BGP routes.

3. Intra-area LSP (LDP/RSVP-TE)
Enhanced Deployment
PE-2
PE-7(R7)
Area 0
Area 1
Area 2
PE-1
ABR-22 (RR)
ABR-12 (RR)
Service Layer
Inner Transport Layer
Outer Transport Layer
VPN Label or PW Label
IP Tunnel
Intra-area LSP (LDP/RSVP-TE)
IBGP
VPN or PW Signaling
ABR-11 (RR)
ABR-21 (RR)
P (RR)
The innermost transport LSP (i.e., BGP signaled LSP) is replaced with an IP tunnel.
Labeled BGP routes for PE routers are replaced with vanilla BGP routes which could be aggegated when crossing domain boundaries.
Egress BGP node protection mechanism is greatly simplified (e.g., ABR11 and ABR12 use an anycast address as the BGP next-hop when LDP is used for establishing intra-domain LSPs).

4. Enhanced Deployment (cont)
PE-2
PE-7(R7)
Area 0
Area 1
Area 2
PE-1
ABR-22
ABR-12
Service Layer
Inner Transport Layer
Outer Transport Layer
VPN Label or PW Label
IP Tunnel (OSPF Route)
Intra-area LSP (RSVP-TE)
VPN or PW Signaling
ABR-11
ABR-21
Shortcut/FA
Shortcut/FA
Shortcut/FA
Shortcut/FA
Shortcut/FA
Shortcut/FA
Shortcut/FA
In the multi-area/level case where IGP short-cut or forwarding-adjacency (FA) feature is available, BGP signaling between ABRs and PE routers can be eliminated further.
As a result, the network provisioning work is simplified further.

5. Enhanced Deployment (cont)
AGN-2
PE-7(R7)
Area 0
Area 1
Area 2
AGN-1
ABR-22 (RR)
ABR-12 (RR)
VPN Label or PW Label
IP Tunnel
Intra-area LSP (LDP/RSVP-TE)
IBGP
VPN or PW Signaling
ABR-11 (RR)
ABR-21 (RR)
P (RR)
AN-1 (PE)
AN-2 (PE)
Static Route
In the target scenario of seamless MPLS, access nodes (AN) just need to perform MPLS-in-IP encapsulation while aggregation nodes (AGN) just need to support BGP free core feature.

6. Next Steps
WG adoption of this draft as an informational draft?