1 LSP-Trace over MPLS tunnels draft-nitinb-lsp-ping-over-mpls-tunnel-01 Nitin BahadurJuniper Networks Kireeti KompellaJuniper Networks George SwallowCisco Systems IETF 70, MPLS WG, Vancouver

2 Tracing a hierarchical LSP ABC E D LDP RSVP Options available at node B: Do not allow tracing inside RSVP LSP Allow tracing inside RSVP LSP

3 Problem scenario (1): Tracing a hierarchical LSP ABCED LDP RSVP Node B’s “effective” next-hop for LDP LSP is node D However the “real” next-hop is node C Node A sends echo request with LDP FEC to node C Node C knows nothing about LDP FEC, so cannot perform FEC validation. Node A cannot tell why it is getting a response from node C

4 Solution ABC E D LDP RSVP Intermediate node (router B) provides a PUSH FEC stack tlv containing in DSMAP of echo response Ingress (router A) pushes RSVP onto it’s FEC stack in echo request when sending next echo request (to router C) When router D receives echo request with FEC stack containing, it sends Egress-Ok for RSVP FEC Implicitly conveys that RSVP LSP is over -- pop it Ingress (router A) now pops an entry from (local) FEC stack and resends echo request to router D with LDP FEC

5 Problem Scenario (II): Tracing a stitched LSP ABCED RSVPLDPeBGPLDP F RSVP No current mechanism to perform end-to-end trace of stitched LSPs. Current trace mechanisms will only trace till router C.

6 Solution Intermediate node (router C) provides a POP FEC stack sub-tlv (LDP) and PUSH FEC stack sub-tlv (eBGP) in DSMAP of echo response. Ingress (router A) performs the corresponding stitch operation and sends eBGP FEC in next echo request (to router D) Router D provides a POP FEC stack tlv (eBGP) and PUSH FEC stack sub-tlv (RSVP) in DSMAP of echo response. Ingress (router A) performs the corresponding stitch operation and sends RSVP FEC in next echo request (to router E) Router F responds with EGRESS_OK for the end-to-end LSP. ABCED RSVPLDPeBGPLDP F RSVP

7 Solution concept Intermediate routers provide ingress information regarding: – start of a new tunnel – end of a tunnel – tunnel stitch. FEC details can be hidden by sending a NIL FEC, instead of actual FEC being pushed. Analogous to push/pop operations in the data-plane. Main logic at ingress application to correctly traverse the tunnels

8 TLV changes proposed … Builds on RFC 4379 (LSP-Ping) Downstream Mapping TLV deprecated –Not extensible: can’t have sub-TLVs (blame Kireeti!) –Not easy to associate new information in echo response Downstream detailed mapping TLV introduced –Similar to previous one –Contains sub-TLVs to represent all variable length things –New sub-TLVs can be added in future to associate things with DSMAP. Procedures outlined to deal with old and new TLV formats.

9 Downstream Detailed Mapping TLV | MTU | Address Type | DS Flags | | Downstream IP Address (4 or 16 octets) | | Downstream Interface Address (4 or 16 octets) | | Sub-tlv length | Reserved | List of Sub TLVs

10 DDMAP Sub-TLVs Multipath Sub-TLV |Multipath Type| Multipath Length | Reserved | | | | (Multipath Information) | Label-stack Sub-TLV | Downstream Label | Protocol | | Downstream Label | Protocol |

11 DDMAP Sub-TLVs (contd.) Stack change sub-TLV |Operation Type| Address type| FEC-tlv length | | Remote Peer Address (0, 4 or 16 octets | FEC TLV Operation Type # Operation Push 2 Pop

12 Next Steps WG feedback on problem/solution Adopt as WG doc ?