Re: [PWE3] [mpls] Seeking feedback on I-D "MPLS-TP Linear Protection Applicability to MS-PW"

Hi Binny,

The assumption is that lower-layer protection (LSP or link protection)
will take care of single-segment failures not affecting S-PEs. The
hold-off mechanism defined in [LinearProt], when properly configured,
prevents MS-PW switchover in this scenario. As you say, this is because
lower-layer protection is more efficient so it should be used when
possible.

Regards,

Daniel

From: mpls-bounces@ietf.org [mailto:mpls-bounces@ietf.org] On Behalf Of
binny jeshan
Sent: Monday, June 13, 2011 3:58 PM
To: Alexander Vainshtein
Cc: pwe3@ietf.org; mpls@ietf.org
Subject: Re: [mpls] [PWE3] Seeking feedback on I-D "MPLS-TP Linear
Protection Applicability to MS-PW"

Hello authors,

I have a generic question on the co-existence of PW monitoring at the
MS-PW level (PSMEG) and the individual segment level (PMEG). Firstly, I
believe there is no such restriction on having co-existence in
monitoring these independently..

Now lets say if a monitored mid segment (a simple PMEG) of a 5 segment
MSPW fails, its quite possible that the PSMEG also detects it at the
endpoints. Now, what would determine the switching priority? Wouldn't it
become costlier if the PSMEG does a MS-PW level switching? Instead, one
could prefer to switch to a backup path at a segment level itself. Is
this addressed?

Thanks,
Binny.

On 13 June 2011 18:13, Alexander Vainshtein
<Alexander.Vainshtein@ecitele.com> wrote:

Dear Ma and all,

Adding the PWE3 WG to my response.

The PW redundancy mechanism supports linear protection of MS-PWs as one
of many additional application use cases:

Appendix A of the PW redundancy Bit draft
<http://datatracker.ietf.org/doc/draft-ietf-pwe3-redundancy-bit/?include
_text=1>  describes 5 application uses cases in addition to MS-PW with
single-homed CEs (which is listed there as use case 5).

And it is equally applicable to IP/MPLS and MPLS - with the help of  the
Static PW Status Messages draft
<http://datatracker.ietf.org/doc/draft-ietf-pwe3-static-pw-status/?inclu
de_text=1> ( if, for whatever reason, you do not want  to, or cannot,
use RFC 4447 <http://datatracker.ietf.org/doc/rfc4447/?include_text=1>
).

Hence I doubt the need for yet another PW redundancy  mechanism with
narrow scope of applicability.

Regards,

     Sasha

From: mpls-bounces@ietf.org [mailto:mpls-bounces@ietf.org] On Behalf Of
ma.yuxia@zte.com.cn
Sent: Monday, June 13, 2011 3:25 PM
To: mpls@ietf.org
Subject: Re: [mpls] Seeking feedback on I-D "MPLS-TP Linear Protection
Applicability to MS-PW"

Hi all, 

The linear protection mechanism for LSP and PW(including MS-PW) should
be the same and it is valuable to describe it clearly. 

BTW, there is a typo, it is "T-PE Z" instead of "T-PE B". 

 " 
  Figure 1 illustrates such a scenario, where two MS-PWs are 
  established between T-PE A and T-PE B, over S-PEs 1-2 and 3-4 
  respectively. Each PW segment is established over an LSP (e.g. PW- 
  s12 over LSP12). 
 " 

-----Original Message-----
From: Daniel Cohn 
Sent: Tuesday, May 17, 2011 4:14 PM
To: mpls
Subject: Seeking feedback on I-D "MPLS-TP Linear Protection
Applicability to MS-PW"
Importance: High

Hi MPLSers,

I uploaded "MPLS-TP Linear Protection Applicability to MS-PW" I-D
(http://tools.ietf.org/html/draft-cohn-mpls-tp-pw-protection-00)

The abstract goes:

One of the requirements of the MPLS transport profile [RFC 5654] is
to provide linear protection for transport paths, which include both
LSPs and PWs. The functional architecture described in [SurvivFwk]
is applicable to both LSP and PWs, however [LinearProt] does not
explicitly describe mechanisms for PW protection in MPLS-TP.

This document extends the applicability of the linear protection
mechanism described in [LinearProt] to MPLS-TP segmented PWs 
(MS-PWs) as defined in [RFC 6073].

Could you please review it and send feedback to the mailing list or
directly to the author? 

Looking forward to your feedback, 

Daniel 

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