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

[Alexander Vainshtein <[e-mail]>]

Hi all,
It seems that GAL, as a technique for identifying OAM packets, could be problematic in MPLS (not MPLS-TP1) environments with enabled ECMP. OAM packets would not necessarily be fate-sharing with the user packets.
Do I miss something?

Regards,
     Sasha





________________________________
From: [e-mail] [[e-mail]] On Behalf Of Shahram Davari [[e-mail]]
Sent: Friday, July 02, 2010 3:19 AM
To: Luca Martini; Andrew G. Malis
Cc: [e-mail]; [e-mail]; HUANG Feng F; [e-mail]
Subject: Re: [mpls-tp] [PWE3] Proposal of using GAL for PW

Hi Luca,

Note that many implementations drop PW packets with GAL label as error packets.

Thanks,
Shahram


From: [e-mail] [mailto:[e-mail]] On Behalf Of Luca Martini
Sent: Wednesday, June 30, 2010 8:23 PM
To: Andrew G. Malis
Cc: [e-mail]; [e-mail]; HUANG Feng F; [e-mail]
Subject: Re: [mpls-tp] [PWE3] Proposal of using GAL for PW

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]> [mailto:[e-mail]] On Behalf Of Larry

Sent: 2010年6月30日 17:38

To: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>

Cc: [e-mail]<mailto:[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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