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

From: [email-masked]
Date: Mon, 13 Jun 2011 20:24:53 +0800

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

---

From: Alexander Vainshtein <[email-masked]>
Date: Mon, 13 Jun 2011 15:43:26 +0300

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/?include_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: [email-masked] [mailto:[email-masked]] On Behalf Of [email-masked]
Sent: Monday, June 13, 2011 3:25 PM
To: [email-masked]
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.

 "

-----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,

The abstract goes:

Daniel

This e-mail message is intended for the recipient only and contains information which is CONFIDENTIAL and which may be proprietary to ECI Telecom. If you have received this transmission in error, please inform us by e-mail, phone or fax, and then delete the original and all copies thereof.

---

From: binny jeshan <[email-masked]>
Date: Mon, 13 Jun 2011 18:28:08 +0530

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 <
[email-masked]> wrote:

> 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/?include_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>
> ).
>
>
>
> *From:* [email-masked] [mailto:[email-masked]] *On Behalf Of
> [email-masked]
> *Sent:* Monday, June 13, 2011 3:25 PM
> *To:* [email-masked]
> *Subject:* Re: [mpls] Seeking feedback on I-D "MPLS-TP Linear Protection
> Applicability to MS-PW"
>
>
>
> Hi all,
>
> This e-mail message is intended for the recipient only and contains
> information which is CONFIDENTIAL and which may be proprietary to ECI
> Telecom. If you have received this transmission in error, please inform us
> by e-mail, phone or fax, and then delete the original and all copies
> thereof.
>
> _______________________________________________
> pwe3 mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/pwe3
>
>

---

From: "Sprecher, Nurit (NSN - IL/Hod HaSharon)" <[email-masked]>
Date: Mon, 13 Jun 2011 15:02:24 +0200

Hi,

I would like to second Sasha.

End-to-end PW protection (with diverse paths) does not scale, and put
hard restrictions on the utilization of the resources.  

MPLS-TP PWs are carried across the network inside MPLS-TP LSPs.
Therefore, an obvious way to provide protection for a PW is to protect
the LSP that carries it.  

If the PW is a multi-segment PW, then LSP recovery can only protect the
PW in individual segments.  This means that a single LSP recovery action
cannot protect against a failure of a PW switching point (an S-PE).

When protecting against an AC or T/S-PE failure by dual connectivity, PW
redundancy mechanisms provide means for the PEs to coordinate over which
LSP the traffic of the PW is carried. 

I also doubt why there is a need for additional mechanism. 

Best regards,

Nurit

From: [email-masked] [mailto:[email-masked]] On Behalf Of
ext Alexander Vainshtein
Sent: Monday, June 13, 2011 3:43 PM
To: [email-masked]
Cc: [email-masked]; [email-masked]
Subject: Re: [PWE3] [mpls] Seeking feedback on I-D "MPLS-TP
LinearProtection Applicability to MS-PW"

Dear Ma and all,

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: [email-masked] [mailto:[email-masked]] On Behalf Of
[email-masked]
Sent: Monday, June 13, 2011 3:25 PM
To: [email-masked]
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. 

 " 

-----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,

The abstract goes:

Daniel 

This e-mail message is intended for the recipient only and contains
information which is CONFIDENTIAL and which may be proprietary to ECI
Telecom. If you have received this transmission in error, please inform
us by e-mail, phone or fax, and then delete the original and all copies
thereof.

---

From: binny jeshan <[email-masked]>
Date: Mon, 13 Jun 2011 19:01:28 +0530

Hello,

Though on one side I'd think its costlier to do a MS-PW level protection
considering the resource usages, pre-configuration and monitoring overload,
on the other i would think - why wouldn't having such a mechanism help in
case if a local repair procedure fails ( failure in protection switch) for a
underlying broken LSP or a mid-PW segment. A provider would never hesitate
look into his pocket to have an end-end level protection considering a risky
situation for an high priority service that he runs on the MS-PW. Wouldn't
he? I believe he could be only concerned in the view of giving precedence to
efficient switching the server layers, and not messing up with multiple
switches happening for one failure.

-Binny.

On 13 June 2011 18:32, Sprecher, Nurit (NSN - IL/Hod HaSharon) <
[email-masked]> wrote:

> End-to-end PW protection (with diverse paths) does not scale, and put hard
> restrictions on the utilization of the resources.
>
> MPLS-TP PWs are carried across the network inside MPLS-TP LSPs. Therefore,
> an obvious way to provide protection for a PW is to protect the LSP that
> carries it.
>
> If the PW is a multi-segment PW, then LSP recovery can only protect the PW
> in individual segments.  This means that a single LSP recovery action cannot
> protect against a failure of a PW switching point (an S-PE).
>
> redundancy mechanisms provide means for the PEs to coordinate over which LSP
> the traffic of the PW is carried.
>
> *From:* [email-masked] [mailto:[email-masked]] *On Behalf Of
> *ext Alexander Vainshtein
> *Sent:* Monday, June 13, 2011 3:43 PM
> *To:* [email-masked]
> *Cc:* [email-masked]; [email-masked]
> *Subject:* Re: [PWE3] [mpls] Seeking feedback on I-D "MPLS-TP
> mpls mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mpls
>
>

---

From: "Sprecher, Nurit (NSN - IL/Hod HaSharon)" <[email-masked]>
Date: Mon, 13 Jun 2011 15:38:48 +0200

Hi,

For end-to-end, you can do it on the client service level. 

If the intention is to protect against a S/T-PE  failure, I think the
solution should be efficient and not necessarily on the end-to-end PW
level. 

We may come soon with idea how to do it. 

Best regards,

Nurit

From: ext binny jeshan [mailto:[email-masked]] 
Sent: Monday, June 13, 2011 4:31 PM
To: Sprecher, Nurit (NSN - IL/Hod HaSharon)
Cc: ext Alexander Vainshtein; [email-masked]; [email-masked];
[email-masked]
Subject: Re: [mpls] [PWE3] Seeking feedback on I-D "MPLS-TP
LinearProtection Applicability to MS-PW"

Hello,

Though on one side I'd think its costlier to do a MS-PW level protection
considering the resource usages, pre-configuration and monitoring
overload, on the other i would think - why wouldn't having such a
mechanism help in case if a local repair procedure fails ( failure in
protection switch) for a underlying broken LSP or a mid-PW segment. A
provider would never hesitate look into his pocket to have an end-end
level protection considering a risky situation for an high priority
service that he runs on the MS-PW. Wouldn't he? I believe he could be
only concerned in the view of giving precedence to efficient switching
the server layers, and not messing up with multiple switches happening
for one failure.

-Binny.

On 13 June 2011 18:32, Sprecher, Nurit (NSN - IL/Hod HaSharon)
<[email-masked]> wrote:

Hi,

Best regards,

Nurit

Dear Ma and all,

Regards,

     Sasha

Hi all, 

 " 

-----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,

The abstract goes:

Daniel

---

From: "Daniel Cohn" <[email-masked]>
Date: Mon, 13 Jun 2011 17:54:56 +0300

Hi,

Thanks all for the feedback. I believe we all agree that PW protection
is only required in the event of S-PE failure at an MS-PW - this  is
clearly stated in the draft. Now, both Sasha and Nurit mention that the
PW redundancy mechanism can meet the MPLS-TP PW protection requirements.

First of all a word on scalability. Please note that in an MPLS-TP
environment without a control plane, the PW redundancy mechanism must
also rely on proactive connectivity check for fast failure detection to
meet the sub-50 ms requirement. Therefore any scalability considerations
that apply to the PW protection draft apply to the PW redundancy draft
as well.

Also wrt scalability, there is no such thing as "scales" or "doesn't
scale" - scalability is not a binary concept. You can say that PW
protection scales worse than LSP protection, just like you can say that
LSP protection scales worse than interface protection. Which didn't stop
IETF from defining LSP protection for scenarios where interface
protection doesn't do the job.

Now let's turn our attention back to whether the PW redundancy draaft
can be used to meet MPLS-TP PW protection requirements. I can identify
the following reasons why in its current form it doesn't:

-          It explicitly ("outside the scope") does not define
protection triggers and how to handle coexisting triggers, as requested
in RFC 5654 (MPLS-TP Requirements), reqs #75, #76 and #79

-          It does not support the ability to distinguish between
different types of triggers (i.e. one end doesn't know why the other end
triggered switch), as requested in RFC 5654 (MPLS-TP Requirements), req
#77

-          It does not define revertive/nonrevertive behavior, as
requested in RFC 5654 (MPLS-TP Requirements), req #64

-          It does not define holdoff support, which is especially
important to avoid race conditions with LSP protection when it exists

-          It doesn't support 1+1 mode, as requested in RFC 5654
(MPLS-TP Requirements), req #65

-          It's a two-phase protocol, with the consequent impact on
timing

-          It doesn't define retransmission of protection coordination
messages, so loss of a single PDU can result in switchover not taking
place, thus not supporting sub-50 ms recovery in this case

In summary, PW redundancy was not designed with TP requirements in mind,
and as such does not meet the TP requirements. Of course modifications
may be introduced, but why reinvent the wheel when there is a protocol
(draft-ietf-mpls-tp-linear-protection-06) in the standards track that
supports all the above requirements and can be applied to MS-PW
protection with minor modifications?

Regards,

Daniel

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Sprecher, Nurit (NSN - IL/Hod HaSharon)
Sent: Monday, June 13, 2011 4:02 PM
To: ext Alexander Vainshtein; [email-masked]
Cc: [email-masked]; [email-masked]
Subject: Re: [mpls] [PWE3] Seeking feedback on I-D
"MPLS-TPLinearProtection Applicability to MS-PW"

Hi,

Best regards,

Nurit

Dear Ma and all,

Regards,

     Sasha

Hi all, 

 " 

-----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,

The abstract goes:

Daniel

---

From: Alexander Vainshtein <[email-masked]>
Date: Mon, 13 Jun 2011 18:10:59 +0300

Daniel and all,
Please see some comments inline below.

Regards,
     Sasha

From: Daniel Cohn [mailto:[email-masked]]
Sent: Monday, June 13, 2011 5:55 PM
To: Sprecher, Nurit (NSN - IL/Hod HaSharon); Alexander Vainshtein; [email-masked]
Cc: [email-masked]; [email-masked]
Subject: RE: [mpls] [PWE3] Seeking feedback on I-D "MPLS-TPLinearProtection Applicability to MS-PW"

Hi,

Thanks all for the feedback. I believe we all agree that PW protection is only required in the event of S-PE failure at an MS-PW - this  is clearly stated in the draft. Now, both Sasha and Nurit mention that the PW redundancy mechanism can meet the MPLS-TP PW protection requirements.

First of all a word on scalability. Please note that in an MPLS-TP environment without a control plane, the PW redundancy mechanism must also rely on proactive connectivity check for fast failure detection to  meet the sub-50 ms requirement. [[[Sasha]]] IMO there is nothing specific to MPLS-TP here. Detecting S-PE failures based on the control plane would  not fast enough.
Therefore any scalability considerations that apply to the PW protection draft apply to the PW redundancy draft as well.[[[Sasha]]] I have not raised the scalability issue. My issue was limited applicability scope when compared to PW redundancy. E.g., the PW redundancy mechanisms take care of dual-homed CEs in SS- and MS-PWs - something that liner protection of PWs cannot do.
Also wrt scalability, there is no such thing as "scales" or "doesn't scale" - scalability is not a binary concept. You can say that PW protection scales worse than LSP protection, just like you can say that LSP protection scales worse than interface protection. Which didn't stop IETF from defining LSP protection for scenarios where interface protection doesn't do the job.

Now let's turn our attention back to whether the PW redundancy draaft can be used to meet MPLS-TP PW protection requirements. I can identify the following reasons why in its current form it doesn't:

-          It explicitly ("outside the scope") does not define protection triggers and how to handle coexisting triggers, as requested in RFC 5654 (MPLS-TP Requirements), reqs #75, #76 and #79
[[[Sasha]]] So what? Definition of triggers is orthogonal to how coordinated protection switching happens.

-          It does not support the ability to distinguish between different types of triggers (i.e. one end doesn't know why the other end triggered switch), as requested in RFC 5654 (MPLS-TP Requirements), req #77

-          It does not define revertive/nonrevertive behavior, as requested in RFC 5654 (MPLS-TP Requirements), req #64

-          It does not define holdoff support, which is especially important to avoid race conditions with LSP protection when it exists

-          It doesn't support 1+1 mode, as requested in RFC 5654 (MPLS-TP Requirements), req #65
[[[Sasha]]] All these claims are correct - and  this should not be a surprise, because MPLS-TP requirements have been defined much later than the PW redundancy mechanism.
But I do not think that this justifies co-existence of two different mechanisms.

-          It's a two-phase protocol, with the consequent impact on timing[[[Sasha]]] Could you please elaborate?

-          It doesn't define retransmission of protection coordination messages, so loss of a single PDU can result in switchover not taking place, thus not supporting sub-50 ms recovery in this case
[[[Sasha]]] The PW redundancy protocol runs either on top of LDP (which benefits from TCP retransmissions) or on top of static PW status messages (where retransmission is defined).

In summary, PW redundancy was not designed with TP requirements in mind, and as such does not meet the TP requirements. Of course modifications may be introduced, but why reinvent the wheel when there is a protocol (draft-ietf-mpls-tp-linear-protection-06) in the standards track that supports all the above requirements and can be applied to MS-PW protection with minor modifications?
[[[Sasha]]] As I said, because the applicability scope is by far too narrow to justify a dedicated protocol.

Regards,

Daniel

From: [email-masked] [mailto:[email-masked]] On Behalf Of Sprecher, Nurit (NSN - IL/Hod HaSharon)
Sent: Monday, June 13, 2011 4:02 PM
To: ext Alexander Vainshtein; [email-masked]
Cc: [email-masked]; [email-masked]
Subject: Re: [mpls] [PWE3] Seeking feedback on I-D "MPLS-TPLinearProtection Applicability to MS-PW"

Hi,
I would like to second Sasha.
End-to-end PW protection (with diverse paths) does not scale, and put hard restrictions on the utilization of the resources.
MPLS-TP PWs are carried across the network inside MPLS-TP LSPs. Therefore, an obvious way to provide protection for a PW is to protect the LSP that carries it.
If the PW is a multi-segment PW, then LSP recovery can only protect the PW in individual segments.  This means that a single LSP recovery action cannot protect against a failure of a PW switching point (an S-PE).
When protecting against an AC or T/S-PE failure by dual connectivity, PW redundancy mechanisms provide means for the PEs to coordinate over which LSP the traffic of the PW is carried.
I also doubt why there is a need for additional mechanism.
Best regards,
Nurit

From: [email-masked] [mailto:[email-masked]] On Behalf Of ext Alexander Vainshtein
Sent: Monday, June 13, 2011 3:43 PM
To: [email-masked]
Cc: [email-masked]; [email-masked]
Subject: Re: [PWE3] [mpls] Seeking feedback on I-D "MPLS-TP LinearProtection Applicability to MS-PW"

Dear Ma and all,

Regards,
     Sasha

Hi all,

 "

-----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,

The abstract goes:

Daniel

---

From: "Sprecher, Nurit (NSN - IL/Hod HaSharon)" <[email-masked]>
Date: Mon, 13 Jun 2011 17:23:25 +0200

If you do it on the client service layer, you can protect also the
T-PE...

Why do you want to protect only against a failure of the S-PE? The PW
starts at the T-PE...

From: ext Alexander Vainshtein [mailto:[email-masked]]

Sent: Monday, June 13, 2011 6:11 PM
To: Daniel Cohn
Cc: [email-masked]; [email-masked]; Sprecher, Nurit (NSN - IL/Hod
HaSharon); [email-masked]
Subject: RE: [mpls] [PWE3] Seeking feedback on I-D
"MPLS-TPLinearProtectionApplicability to MS-PW"

Daniel and all,

Regards,

     Sasha

From: Daniel Cohn [mailto:[email-masked]] 
Sent: Monday, June 13, 2011 5:55 PM
To: Sprecher, Nurit (NSN - IL/Hod HaSharon); Alexander Vainshtein;
[email-masked]
Cc: [email-masked]; [email-masked]
Subject: RE: [mpls] [PWE3] Seeking feedback on I-D
"MPLS-TPLinearProtection Applicability to MS-PW"

Hi,

First of all a word on scalability. Please note that in an MPLS-TP
environment without a control plane, the PW redundancy mechanism must
also rely on proactive connectivity check for fast failure detection to
meet the sub-50 ms requirement. [[[Sasha]]] IMO there is nothing
specific to MPLS-TP here. Detecting S-PE failures based on the control
plane would  not fast enough.

Therefore any scalability considerations that apply to the PW protection
draft apply to the PW redundancy draft as well.[[[Sasha]]] I have not
raised the scalability issue. My issue was limited applicability scope
when compared to PW redundancy. E.g., the PW redundancy mechanisms take
care of dual-homed CEs in SS- and MS-PWs - something that liner
protection of PWs cannot do.

[[[Sasha]]] So what? Definition of triggers is orthogonal to how
coordinated protection switching happens.

[[[Sasha]]] All these claims are correct - and  this should not be a
surprise, because MPLS-TP requirements have been defined much later than
the PW redundancy mechanism. 

But I do not think that this justifies co-existence of two different
mechanisms.

-          It's a two-phase protocol, with the consequent impact on
timing[[[Sasha]]] Could you please elaborate? 

[[[Sasha]]] The PW redundancy protocol runs either on top of LDP (which
benefits from TCP retransmissions) or on top of static PW status
messages (where retransmission is defined). 

[[[Sasha]]] As I said, because the applicability scope is by far too
narrow to justify a dedicated protocol.

Regards,

Daniel

Hi,

Best regards,

Nurit

Dear Ma and all,

Regards,

     Sasha

Hi all, 

 " 

-----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,

The abstract goes:

Daniel

---

From: Maarten vissers <[email-masked]>
Date: Tue, 14 Jun 2011 11:41:22 +0000

Nurit,

If I translate your proposal in terms of SDH protection, then your proposal would imply that LOVC (e.g. VC-12, VC-11 protection should not be deployed, instead only HOVC (VC-4, VC-3) protection should be deployed. We all know that the SDH network has many protected LOVC connections, and that this is scaling well. My question is therefore why protecting MS-PW connections (and Service-LSP connections) would not scale?

Regards,
Maarten

From: [email-masked] [mailto:[email-masked]] On Behalf Of Sprecher, Nurit (NSN - IL/Hod HaSharon)
Sent: 13 June 2011 15:02
To: ext Alexander Vainshtein; [email-masked]
Cc: [email-masked]; [email-masked]
Subject: Re: [mpls] [PWE3] Seeking feedback on I-D "MPLS-TP LinearProtection Applicability to MS-PW"

Hi,

Dear Ma and all,

Regards,
     Sasha

Hi all,

 "

-----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,

The abstract goes:

Daniel

---

From: "Daniel Cohn" <[email-masked]>
Date: Tue, 14 Jun 2011 14:44:00 +0300

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: [email-masked] [mailto:[email-masked]] On Behalf Of
binny jeshan
Sent: Monday, June 13, 2011 3:58 PM
To: Alexander Vainshtein
Cc: [email-masked]; [email-masked]
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
<[email-masked]> wrote:

Dear Ma and all,

Regards,

     Sasha

Hi all, 

 " 

-----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,

The abstract goes:

Daniel