Re: [mpls] [mpls-tp] mpls wg last call on draft-ietf-mpls-tp-linear-protection-04

Dear authors,

Here are some comments on linear protection draft.

1. In section 1.2, it says:
" The basic protocol is designed for use in conjunction with the 1:1
protection architecture (for both unidirectional and bidirectional
protection) and for 1+1 protection of a bidirectional path (for both
unidirectional and bidirectional protection switching). "

Would you please explain why coordination is needed for unidirectional
protection switching in 1+1 protection of a bidirectional path? Because
section 4.7.2 of tp-survive-fwk says:
"In 1+1 unidirectional protection switching there is no need to coordinate
the protection state between the protection controllers at both ends of the
protection domain."

I guess you mean 1+1 protection may need coordination to keep traffic on
co-routed paths, but that would be bidirectional protection switching.
Hope this could be made clearer in this draft.

2. Section 2.1, Acronyms
The full name of "LER" should be "Label Edge Router"
"PST" is an old term replaced by SPME (Sub-Path Maintenance Entity), but
neither is used in the following sections, so it may be removed from
acronyms.

3. In Section 3, there is only one level-2 subsection (3.1), so what about
promote the level-3 subtitles (3.1.1, 3.1.2, ...) to level-2, and level-4
(3.1.6.1) to level-3?

4. Section 4, 3rd paragraph, s/single-phase/single-phased, to be consistent
with 2nd paragraph.

5. Section 4.1, 4th paragraph,
" In the event a signal fail condition is detected on the protection path,
the received PSC specific information should be evaluated."
The statement is vague. What would be the state and action when a signal
fail is detected on the protection path? Would you please elaborate on this
point?

6. Section 4.2.2, 4th paragraph,
" The Fpath field SHALL identify the path that is reporting the failure
condition (i.e. if protection path then Fpath is set to 0...".
Since PSC message are only transmitted on protection path, if protection
path has signal fail, the PSC message may not be able to be sent out to
far-end.

7. Section 4.3.2, there is signal degrade on working path as input, but no
signal degrade on protection path.

8. Section 4.3.3, I go through this part fast, a general question is: are
the PSC operations for 4 different protection types identical ? In this
section there is no description about operation of each specific protection
type, but to my understanding, there may be different operations, e.g., for
bidirectional 1:1 protection, the end point may need to switch the sink
selector and transmitting bridge simultaneously according to some input, but
for unidirectional 1:1 the end point may only need to switch the
transmitting bridge OR the sink selector. And the PSC message sent may also
be different for different protection types. (Please correct me if there is
anything wrong with this thought).

Best Regards,
Jie

> -----Original Message-----
> From: mpls-tp-bounces@ietf.org [mailto:mpls-tp-bounces@ietf.org] On
> Behalf Of Loa Andersson
> Sent: Thursday, February 03, 2011 7:42 PM
> To: mpls-tp@ietf.org; mpls@ietf.org
> Cc: ahmpls-tp@lists.itu.int
> Subject: [mpls-tp] mpls wg last call on
draft-ietf-mpls-tp-linear-protection-04
>
> Working Group,
>
> this is to start a four week working group last call on
> "MPLS-TP Linear Protection" (draft-ietf-mpls-tp-linear-protection-04).
>
> Please send comments to the mpls-tp@ietf.org mailing list.
>
> This working group last call ends on February 28, 2011.
>
>
>
> Loa, George and Ross
>
> MPLS wg co-chairs
>
>
>
> --
>
>
> Loa Andersson                         email:
> loa.andersson@ericsson.com
> Sr Strategy and Standards Manager            loa@pi.nu
> Ericsson Inc                          phone: +46 10 717 52 13
>                                               +46 767 72 92 13
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