Subject: [mpls-tp] draft-boutros-mpls-tp-loopback

From: Vishwas Manral <[email-masked]>
Date: Sun, 11 Apr 2010 21:40:40 -0700

Hi,

I have the following comments:

1. Introduction section:

      C loops only the OAM control packets (those OAM control packets
      will be identified by an ACH code point and will be generated
      by node A) back to A, and all other packets from A are sent
      towards C. We refer to this mode "OAM Loopback" (OLB).

I think it should be sent towards D.

2. The document states that:

   In FLB mode the input LSP from the direction of A is directly cross-
   connected to the output LSP towards A.  All the packets generated by
   node A (data and control) are looped back at C, excepting the case of
   TTL expiration.

I think it should be made clear that even when the loopback is to be
done on the MEP(LSP Egress) we should only use the TTL expiry
mechanism to send Loopback messages. Better still all ACH exception
messages need to be looped back.

However it is stated that:

   If the target ME is a MEP, the value MUST be set to
   at least the number of hops required to reach that MIP.  For most
   operations where the target is a MEP, the TTL MAY be set to 255.

If the TTL is set to 255 the packet will not be looped back as only
TTL messages are looped back.

3. Also like the comments I have given for other drafts it seems that
the draft does not consider the case where a control packet will be
dropped. I think we need to make clear the behavior when a particular
control packet is lost.

Otherwise the draft looks good.

Thanks,
Vishwas