Subject: [mpls] OPSDIR review of draft-ietf-mpls-tp-linear-protection-07.txt

From: Bert Wijnen <[email-masked]>
Date: Tue, 12 Jul 2011 14:35:00 -0000

[note that I am not on the MPLS WG mailing list, so cc me explicitly
if you want me to see any reactions/responses. I am on the ops-dir
list though).

Hi,

I was asked to do an ops-dir review of document
draft-ietf-mpls-tp-linear-protection-07.txt.

I think the document is in good shape. From an operations
and management point of view I have these comments:

There is one operational aspect mentioned in section
4.1, namely:

    The frequency of the three rapid messages and the separate frequency
    of the continual transmission SHOULD be configurable by the operator.
    For protection switching within 50ms, it is RECOMMENDED that the
    default interval of the first three PSC messages SHOULD be no larger
    than 3.3ms.  The subsequent messages SHOULD be continuously
    transmitted with an interval of 5 seconds.

It might be good to explain the rationale for the RECOMMENDED intervals.
And maybe some explanation as to what considerations need to be
taken into account when configuring these values.

has the WG considered to standardize the configurability of these
frequencies? Or is it left (intentionally?) to each implementation how
this is done?
Can an operator (or an NMS) easily see what the values are at the various
LERs?

Bert Wijnen

---

From: <[email-masked]>
Date: Mon, 1 Aug 2011 15:38:43 +0900

Hi Yaacov,

I put two comments in this list on draft-ietf-mpls-tp-linear-protection
as we discussed in Quebec.

1. PSC protocol version field
You should infom the reason why you have changed the protocol version
from 0 to 1 in the draft-08.
This is very important to implement PSC protocol.

2. Priorities of SF-P and FS
You said;
It is possible to give higher priority of FS than SF-P
in the next version of this draft.
It's because, in the current draft, it is impossible to keep selecting
a protection path securely, even in the case of SF on the protection path.

I think it's reasonalble.
However, due to this change, a race condition will bother us.
It's because an operator has to input the FS command to both ends of connection. 
You should explore the solution to avoid the race condition.

BR,
Hideki