February 2006 MPLS Interop 2008 # 1 MPLS-TP OAM OAM for an MPLS Transport Profile Loa Andersson, Acreo AB IAB, MPLS WG co-chair

February 2006 MPLS Interop 2008 # 2 MPLS-TP Starting points PHP is part of the MPLS architecture –It is a powerful –It solves more problems than it creates –Removing it creates more problems than it solves –We should try ti see how we can use the PHP, rather than to remove it

February 2006 MPLS Interop 2008 # 3 MPLS-TP OAM Forwarding TLTL’ TL PHP TL TL’ TL PHP TL TL’PHP TL MEPABMIP-1CMIP-2DMEP TTTT-1TT-2TT-3 TL’

February 2006 MPLS Interop 2008 # 4 Legend for the previous slide The “cylinder” indicates links between LSRs. At an ingress LSR one or more labels are pushed onto a packet At intermediate LSRs labels are swapped At pen ultimate LSRs Labels are popped At egress LSRs actions are taken on the top label The LSRs are in the gaps between the links. LSRs that don’t have a MEP or MEP are called A, B, C and D, if they have the are called MEP or MIP The thinner cylinder represents the OAM channel

February 2006 MPLS Interop 2008 # 5 Naming of tunnels The outermost (top of label stack) tunnel is called Transport Tunnel (TT) Transport Tunnels that is carried in other Transport Tunnels is called TT-n In the figures we have TT, TT-1, TT-2 and TT-3 On every level below the TT it is possible to multiple TTs, e.g. TT-1, TT-1’, TT-1’’ etc. There is only a single tunnel for OAM between a pair of MEP and MEP/MIP.

February 2006 MPLS Interop 2008 # 6 Forwarding When a LSR sends a packet across the transport LSP it pushes the entire Label stack needed. When a packet reaches the pen-ultimate hop of the current of a transport LSP level, the top label is popped and the packet forwarded with the next label on top At the egress LSR the packet is forwarded based on the label on the top of the stack

February 2006 MPLS Interop 2008 # 7 MPLS-TP OAM MEP to MEP TLTL’ TL PHP TL TL’ TL PHP TL TL’PHP MEPABMIP-1CMIP-2DMIP-3 TTTT-1TT-2TT-3 TL TL’TL MEP LFU FLULFU

February 2006 MPLS Interop 2008 # 8 Communication MEP to MEP When an MEP sends an OAM packet the LSR pushes a label stack where the transport label that is comes to the top of the stack at the PHP before the MIP that the OAM packet is addressed to is replaced by the LFU When a packet with the LFU at the top of the stack is received the LSR locates the ACH after the label with the BoS bit set Apart from information indicating what OAM procedures that is required the ACH needs to carry information on what LSP this is requested for, this may require an aggreate LSPid

February 2006 MPLS Interop 2008 # 9 MPLS-TP OAM MEP to MIP-1 TLTL’ PHP LFU MEPABMIP-1CMIP-2DMEP

February 2006 MPLS Interop 2008 # 10 MPLS-TP OAM MEP to MIP-2 TLTL’ TL PHP TL TL’PHP LFU FLULFU MEPABMIP-1CMIP-2DMEP

February 2006 MPLS Interop 2008 # 11 MEP to MIP communication The only difference between MEP to MIP communication and MEP to MEP communication is that the label stack only needs to be populated to take the the packet to the LSR with the MIP, the rest of the label stack may be omitted. If the redundant part of the label stack is present the LFU will not have the BoS set The MPLS architecture has been operating with uni- directional LSPs. This works for bi-directional LSPs as well. It is not clear if the response OAM channel needs to be bundled with the LSP in the reverse direction or if direct communication between originating MEP and the responder is allowed. Both schemes works with this architeture.

February 2006 MPLS Interop 2008 # 12 Questions Is MIP to MIP communication needed? Is MIP to MEP communication needed for other purposes than responses on communications that were initiated by the MEP? If one set up LSPs from a NMS or manually this is fiarly straightforward. If one is using a control plane it might require extensions to the signaling protocol, especially the concept of an aggregate LSPid needs to be investigated.