Re: [PWE3] Tandem Connection Monitoring in the new PWE3 Chapter

Stewart,

TCM is not hard to make work, as we have been proving in OTN and Ethernet
where we have included this capability from the begin. 

In SDH it was hard to add TCM to a large existing network, as this TCM
capability was developed 4 years after the initial SDH specification was
approved. 
By that time lots of LO VC equipment was in the network that could not be
upgraded. 

Regards,
Maarten

-----Original Message-----
From: pwe3-bounces@ietf.org [mailto:pwe3-bounces@ietf.org] On Behalf Of
Stewart Bryant
Sent: 10 July 2008 12:51
To: Alexander Vainshtein
Cc: neil.2.harrison@bt.com; pwe3@ietf.org; Jeremy Brayley; Danny McPherson;
Alik Shimelmits
Subject: Re: [PWE3] Tandem Connection Monitoring in the new PWE3 Chapter

Alexander Vainshtein wrote:
>  Stewart, Danny and all,
>
>   
>> -----Original Message-----
>> From: pwe3-bounces@ietf.org [mailto:pwe3-bounces@ietf.org] On Behalf 
>> Of neil.2.harrison@bt.com
>> Sent: Wednesday, July 09, 2008 10:18 PM
>> To: mohand@nortel.com; sajassi@cisco.com
>> Cc: pwe3@ietf.org; stbryant@cisco.com
>> Subject: Re: [PWE3] draft-mohan-pwe3-mpls-eth-oam-iwk-00.txt
>> as WG draft
>>
>>     
> ... snipped ...
>   
>> I've just noticed TCM (Tandem Connection Monitoring) has been added 
>> to the
>> PWE3 charter.  I would strongly advise IETF *not* to go here just 
>> because others have included this in their standards.  This idea has 
>> been around for many years in ITU and there are very good reasons why 
>> very little of it is used in practice (I can spell this out if not 
>> obvious).
>>
>> Regards, Neil
>>
>>     
> ... snipped to the end...
>
> I wonder how Tandem Connection Monitoring for PWs has made its way 
> into the published Charter as one of the milestones. It is not 
> discussed/defined in the Charter itself and it has not been mentioned 
> on the WG mailing list for the last 7+ months (including the versions of
the Charter posted for the WG discussion during the re-chartering process).
>
> I share Neil's concerns about this topic. In particular, Low-Order 
> Path TCM (defined by ITU-T in addition to the SONET High-Order Path 
> TCM) is a feature known both for implementation complexity and lack of
actual deployments... Do we really need more of the same in PWE3?
>
> Regards,
>         Sasha
>
>
>   
Sasha

TCM for PWs is in the JWT report: draft-bryant-mpls-tp-jwt-report-00.pdf

It was added when we were asked to flesh out deliverables to support
MPLS-TP.

If as you and Neil suggest it's hard to make work, then that will be clear
if/when we see drafts defining it, and we can proceed accordingly.

- Stewart

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