Re: [mpls-tp] [PWE3] Proposal of using GAL for PW

[Sam Aldrin <[e-mail]>]

As deployments with no CW already exist, mandating CW in not a  
preferred option. Also, I believe, mandating CW just to support OAM is  
an overkill.

Were the Multi-segment scenarios considered here? Not all the segments  
necessarily support CW, whereby, having GAL label support is a better  
option.

cheers
-sam
On Jul 1, 2010, at 10:08 AM, Shahram Davari wrote:

> Hi,
>
> I agree with Andy and Tom. The best way forward is to mandate  
> control word (VVCV Type 1) for future implementations, rather than  
> introduce VCCV Type 4.
>
> Thanks,
> Shahram
>
> From: [e-mail] [mailto:[e-mail]] On  
> Behalf Of Thomas D. Nadeau
> Sent: Thursday, July 01, 2010 6:31 AM
> To: Giles Heron; Luca Martini; Andrew G. (Andy) Malis
> Cc: [e-mail]; [e-mail]; HUANG Feng F; [e-mail]
> Subject: Re: [mpls-tp] [PWE3] Proposal of using GAL for PW
>
>
>
>
> On 7/1/10 9:22 AM, "Giles Heron" <[e-mail]> wrote:
>
> Not sure I agree.
>
> Many CPs have deployed PWs with no CW.   Adding a CW to all packets  
> just to enable occasional OAM messages seems like overkill.
>
> TOM: The question would be in those cases: do those CPs have multi- 
> vendor implementations and how difficult is it for them to handle  
> operational issues as well as interoperability of those  
> implementations?  The operators that have presented/discussed this  
> at the last PWE3 meeting seemed to voice a resounding desire to have  
> a consistent method rather than 3, 4 or N options.
>
> But the downside of adding GAL is that it’s a fourth OAM mode  
> for PWEs (back to your point about interoperability).  Too many  
> options!
>
> TOM: Precisely the point of requiring one way to do things.  Too  
> many options is ok to get the kinks worked out of implementations,  
> but going forward it seems better to narrow things as Andy’s  
> original note asserted.
>
>     --Tom
>
>
>
> Giles
>
> On 01/07/2010 12:14, "Tom Nadeau" <[e-mail]> wrote:
>
>
>     I  agree with Andy’s assertion. This service  
> provider’s experience is that making the CW mandatory going  
> forward (and hopefully retrofitting existing PW protocol specs)  
> would improve implementation interoperability.
>
>     --Tom
>
>
>
> On 6/30/10 11:22 PM, "Luca Martini" <[e-mail]> wrote:
>
> Andy,
>
> I have to disagree that there was any consensus about this issue.
> If anything , there was consensus that there is no written statement  
> that we must  to use the CW in MPLS-TP.
>
> At the end we needed more input from service providers that have  
> deployed PWs.  The point is not whether there is hardware support  
> for the CW, but whether we even want to use it in many cases where  
> it adds absolutely no value. For example ATM PWs in cell mode ,  
> where it add almost 10% overhead with no benefit. Another case where  
> the CW is not useful is the ethernet PW without network link load  
> balancing, where we add 4 bytes to every packet just to occasionally  
> send a status , or OAM message.
>
> I would like to propose update the rfc5586 to allow the use of the  
> GAL in PWs without the CW.
>
> This makes the use of the GAL very symmetric among PWs and MPLS-TP  
> LSPs. This makes it easy to process by hardware based implementations.
>
> Luca
>
>
> Andrew G. Malis wrote:
>
> Larry and Feng,
>
> This issue has previously been discussed at length by the working
> group, both at the Anaheim meeting and by email, for example in emails
> with the subject line "Possible Contradiction re use of GAL in
> pwe3-static-pw-status". There was rough consensus that for MPLS-TP
> applications and/or when PW OAM is desired, PW implementations are
> mature enough (it has been 10 years now, after all) that the time has
> come to require the implementation of the CW for all PWs, including
> Ethernet.
>
> Cheers,
> Andy
>
> On Wed, Jun 30, 2010 at 6:34 AM, HUANG Feng F
> <[e-mail]> <mailto:[e-mail] 
> >  wrote:
>
>
>
> it is reasonable to support GAL in MPLS-TP PW OAM, it is more  
> generic, because CW is an option RFC4448 for Ethernet over MPLS.
>
> 4.6.  The Control Word
>
> xxxx
>
>
> The features that the control word provides may not be needed for a
>   given Ethernet PW.  For example, ECMP may not be present or active  
> on
>   a given MPLS network, strict frame sequencing may not be required,
>   etc.  If this is the case, the control word provides little value  
> and
>   is therefore optional.  Early Ethernet PW implementations have been
>   deployed that do not include a control word or the ability to  
> process
>   one if present.  To aid in backwards compatibility, future
>   implementations MUST be able to send and receive frames without the
>   control word present.
> xxxx
>
>
>
> B.R.
> Feng Huang
>
>
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf  
> Of Larry
> Sent: 2010年6月30日 17:38
> To: [e-mail]; [e-mail]
> Cc: [e-mail]
> Subject: [PWE3] Proposal of using GAL for PW
>
> Dear all:
>
>     In section 4.2 in RFC5586, it is defined that GAL MUST NOT be  
> used with PWs in MPLS-TP. The PWE3 control word [RFC4385] MUST be  
> present when the ACH is used to realize the associated control  
> channel.
>     In real application, a lot of MPLS and MPLS-TP equipments do not  
> support control word. It is proposed to use the GAL to identify  
> associated control channel in PW layer.
>
> Best regards,
>
>                 Han Li
>
> ********************************************************************
> Han Li, Ph.D
> China Mobile Research Institute
> Unit 2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China
> Fax: [phone]
> MOBILE: [phone]
> ********************************************************************
>
>
>
>
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