Subject: [mpls-tp] Comments on draft-boutros-mpls-tp-li-lb-01

From: Muralidhar Annabathula <[email-masked]>
Date: Tue, 21 Sep 2010 17:29:00 -0700

Dear Authors,

I have some comments on draft-boutros-mpls-tp-li-lb-01 (I could not locate
the WG doc for the same, not sure if its published yet).

1) Section 1. Introduction

"...The mechanisms in this document apply to
   associated bidirectional paths as defined in [7], which include MPLS-
   TP LSPs, bi-directional RSVP-TE tunnels, pseudowires (PW), and Multi-
   segment PWs."

[Murali] Its not clear if we are refering to co-routed bidirectional paths
ONLY. if not how is loopback possible at MIPs on associated bidirectional
LSPs (non-corouted), there may/may not be a reverse LSP.

2) Section 3.1 In-band Message Identification.
"...The LI-LB Channel does not use ACH
  TLVs and MUST not include the ACH TLV header."
[Murali] If no TLVs like How will the recepient of the loopback request
validate if the loopback request is indeed addressed for it without using
MEP/MIP ID TLV. Only using TTL expiry may not be enough? Also there are
multiple references to MEP/MIP ID in the document, are we refering to
MEP/MIP ID TLVs?

3) Section 3.2
Mesage ID
"...A sender SHOULD increment this value on each new message.
   A retransmitted message SHOULD leave the value unchanged."
[Murali] Under what conditions will the message be retransimitted? There are
no timer mechanisms defined which can keep track on unanswered/lost requests
and retransmit.

4) Section 3.2
Cause codes
  - Fail to match target MIP/MEP ID
[Murali] If no MIP/MEP IDs are allowed where is the use of this cause code
expected?

5) When using inband signaling what should the behaviour of Source MEP when
some of the responses to lock/unlock or set_loopback/unset_loopback requests
are lost/not sent due to the unavailablility of reverse lsp?
Retransimissions or something similar is planned?

6) When using inband signaling what should be the behaviour of Source MEP
when it receives responses with incorrect sender handle/message-id?

Regards,
Murali