Scalability for LDP over RSVP and BGP labelled unicast services

This feature enhances RPD to produce the chain nexthop for various services. The RPD is enhanced to do build a translation layer between RIB and FIB to segment multi-protocol transport tunnels.

Segmentation happens as follows:

• Only LDP, RSVP, LDP-over-RSVP, LDP-over-RSVP-over-BYPASS ingress tunnels are considered for segmentation.
• Segmentation does not happen if there is only one label in the stack.
• Segmentation happens at the app boundary. A nexthop with two LDP labels in its stack or two RSVP labels will not be split into two nexthops with one label each.

Any route resolution over LDP or LDP-over-RSVP is changed from INH->FNH to CNH->INH->CNH->FNH in kernel and PFE and for LDP routes in INET.3. Where indirect nexthop (INH) is an application installed in direction towards the final nexthop (FNH). Any segmented stack introduces the composite chain nexthop (CNH) where the segmented portion of the label stack precedes an INH, or an FNH. The chain is collapsed and the resulting label stack is encoded in the packet header by the hardware before forwarding the packet.

By chaining labels instead of stacking them, memory is made available for FNH label operations, as well as CNH by grouping CNHs within the same unilist nexthop (for ECMP) based on the label space identifier.

The following applications are supported:

• Transit
• LBGP stitching with LDP over RSVP
• Ingress
• 6PE BGP-V6-Route->LBGP(Explicit V6 NULL label) over LDP over RSVP
• 4PE BGP-V4-Route->LBGP(Explicit V4 NULL label) over LDP over RSVP
• BGP-L3VPN over LDP over RSVP
• BGP-V6-VPN over LDP over RSVP
• BGP route with indirection resolving over LDP over RSVP
• IBGP-V4-ROUTE over LDP over RSVP
• IBGP-V6-ROUTE over LDP over RSVP