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LDP signaled LSPs for external prefixes

Ina Minei, Nischal Sheth - Juniper ina@juniper.net, nsheth@juniper.net Luyuan Fang – AT&T luyuanfang@att.com. LDP signaled LSPs for external prefixes. The problem. LDP relies on routing protocols for its forwarding decisions.

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LDP signaled LSPs for external prefixes

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  1. Ina Minei, Nischal Sheth - Juniper ina@juniper.net, nsheth@juniper.net Luyuan Fang – AT&T luyuanfang@att.com LDP signaled LSPs for external prefixes

  2. The problem • LDP relies on routing protocols for its forwarding decisions. • To establish LSPs, LDP needs routing table entries for all its FECs. • Not always desirable…

  3. The goal • Establish LSPs for FECs that are “external” to the routing table. • Thus, no need to inject external routes corresponding to the LDP FECs in the IGP just for the purpose of LSP establishment.

  4. Before we start… • The discussion is only for address prefix FECs and host FECs associated with IPv4/IPv6 prefixes.

  5. The idea • If LSRa is the one who is injecting FECa into LDP, can use LSRa’s address in the forwarding decision making process. • Don’t need FECa’s address in the routing table, only need LSRa’s address.

  6. The concepts • Decouple the FEC from the routing table entry. • Specify a different address on which to apply the decision making process of whether to use the label for forwarding and whether to propagate the FEC to the neighbors.

  7. LDP extensions • New TLV (Originator Nexthop TLV) specifying the address to use in the forwarding-state decision-making process. • Extensions to the message handling procedures to take advantage of the new TLV.

  8. Originator Nexthop TLV • Carries a host address • Always shows up together with the FEC TLV • Used in label map, withdraw, release messages.

  9. Label mapping procedures Existing algorithm • Conditions for using a label for forwarding: • the routing table contains an _exact_ entry for the address in the FEC TLV • the mapping was received from the neighbor that is the nexthop for the route found in (1).

  10. Label mapping procedures Extension to the algorithm • Conditions for using a label for forwarding if the label-map message contains the Originator Nexthop TLV: • the routing table contains an _exact_ entry for the address in the Originator TLV. • the mapping was received from the neighbor that is the nexthop for the route found in (1).

  11. Label withdraw/release Extension to the algorithm • If the label-map message contained the Originator Nexthop TLV then the withdraw/release must also contain it.

  12. What next? • Gauge interest • Please send comments to the list. • Accept as WG document?

  13. Thank you!

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