Subject: [mpls] Questions RE: draft-ietf-mpls-tp-cc-cv-rdi-03

From: Greg Mirsky <[email-masked]>
Date: Thu, 24 Mar 2011 17:51:46 -0700

Dear Authors,
am I late for WG LC? Hope you'll kindly consider my comments, questions
below.

   - I think that "MPLS Proactive CV" is not the most descriptive tag for CV
   mode ACH code point because, as mentioned in Section 3, both CV and CC
   messages allowed when this ACH used. I propose to name ACH code point for CV
   mode "MPLS Proactive CC/CV" as in Figure 1 ACH Indication of MPLS-TP
   Connectivity Verification. I'd note that in Figure 3 ACH should be changed
   from "0xHH BFD CV Code Point" to "0xHH BFD CC/CV Code Point". And it might
   be useful to add new Diag code "Unintended connectivity error" and request
   code point from BFD registry.
   - Since IP encapsulation of BFD proactive CC/CV can be used then it might
   be helpful to mention that proactive CC/CV operates in CV mode supporting CC
   and CV functions. As for RDI, interpretation of Diag value 3 "Neighbor
   Signaled Session Down" might not be consistent with one given in the
   document as "a consequence of the sink MEP receiving AIS with LDI set". It
   could be that Diag value 5 "Path Down" is better suited to be used as
   indication of MEP receiving AIS with LDI being set.
   - Section 3.5.1 states that messages in DOWN and INIT states transmitted
   at rate one per second, "In both the DOWN and INIT states messages are
   transmitted at a rate of one per second ..." But the second part of the
   sentence refers Detection Time to both states even though it has
   significance, as in RFC 5880, only in the INIT state "... and the defect
   detection interval is fixed at 3.5 seconds". Perhaps if the sentence split
   in to will make it stricter:

"In both the DOWN and INIT states messages are transmitted at a rate of one
per second. Defect Detection Time in INIT state is fixed at 3.5 seconds".

Regards
Greg