Hello Santosh, Thanks for your careful review. You bring up a valid point, that needs clarification. Even without multiple BFD sessions on the <FEC, LSP> if the egress were to inform about a BFD session going to DOWN (potentially using the diag code 0x4 - Neighbor Signalled Down), the YourDisc field needs to be non-zero, so the ingress can demux the packet to the correct session. With multiple sessions per FEC, LSP, this becomes absolutely needed, as you remark below. Could we consider adding the following statement: The egress MUST use the discriminators exchanged when the session was brought to indicate a session DOWN back to the ingress. The egress SHOULD reset this to zero after transmitting detectMult number of packets. Please suggest your thoughts on making the above text better. Thanks Prasad Copying the list for their inputs as well.
-----Original Message----- From: Santosh P K [mailto:[email protected]] Sent: Thursday, May 14, 2015 7:44 PM To: [email protected] Cc: Jeffrey Haas; Nobo Akiya Subject: RE: Working Group Last Call for draft-ietf-bfd-rfc5884-clarifications Hello Authors, Sorry for being so late in the game. I had few points which are not clear from draft. As per RFC 5880 section 6.8.1 it says that when BFD session goes down due to control timer expiry then remote discr MUST be set to 0. <SNIP> " bfd.RemoteDiscr The remote discriminator for this BFD session. This is the discriminator chosen by the remote system, and is totally opaque to the local system. This MUST be initialized to zero. If a period of a Detection Time passes without the receipt of a valid, authenticated BFD packet from the remote system, this variable MUST be set to zero." <SNIP> As per RFC 5884 it says that all the demux MUST happen with remote Discriminator and also it talks about Discr not changing only when session is UP. <SNIP> Section 7: Note that once the BFD session for the MPLS LSP is UP, either end of the BFD session MUST NOT change the source IP address and the local discriminator values of the BFD Control packets it generates, unless it first brings down the session. <SNIP> As per clarification draft " draft-ietf-bfd-rfc5884-clarifications" section 2.4 iterates the same statement. <SNIP> Section 2.4: The discriminators of a BFD session established over an MPLS LSP cannot be changed when it is in UP state. <SNIP> Problem: Now for example if we have multiple LSP's with the same FEC then at egress it might be sending packet to same designation address. In this case if one of the BFD session goes down on egress then it would send BFD packet with down state with 0 discr. Seeing this ingress would try to demux with IFL and source address on the packet, this will lead to multiple sessions. I think this needs to be clarified as well. I am not sure if this point is already covered or not. Do you think it is worth clarifying this point? I think it plays very important role in bringing down the BFD session in MPLS environment. Any thoughts? Thanks Santosh P K > -----Original Message----- > From: Rtg-bfd [mailto:[email protected]] On Behalf Of Jeffrey > Haas > Sent: Tuesday, May 05, 2015 1:28 AM > To: [email protected] > Cc: [email protected] > Subject: Working Group Last Call for > draft-ietf-bfd-rfc5884-clarifications > > The BFD mailing list has been quiet since shortly after IETF 92. We > have a number of documents that seem stable and ready to advance. > > This email begins a two week Working Group Last Call for > draft-ietf-bfd- rfc5884-clarifications-01, Clarifications to RFC 5884. > > This last call will end on May 15. > > Simultaneously, the authors of this draft should state to the mailing > list whether there is any IPR associated with this draft or not. > > This WGLC is also being cc'd to mpls@ietf to permit additional > commentary
