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

[Luca Martini <[e-mail]>]

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]> 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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