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

hi,all
i think that cw should be option part ,
we should consider to be compatible with old equipments

best regards
liu

"Shahram Davari" <davari@broadcom.com> 
发件人:  mpls-tp-bounces@ietf.org
2010-07-02 01:08

收件人
"Thomas D. Nadeau" <tom.nadeau@bt.com>om>, "Giles Heron" 
<giles.heron@gmail.com>om>, "Luca Martini" <lmartini@cisco.com>om>, "Andrew G. 
(Andy) Malis" <amalis@gmail.com>
抄送
"lihan@chinamobile.com" <lihan@chinamobile.com>om>, "pwe3@ietf.org" 
<pwe3@ietf.org>rg>, HUANG Feng F <Feng.f.Huang@alcatel-sbell.com.cn>cn>, 
"mpls-tp@ietf.org" <mpls-tp@ietf.org>
主题
Re: [mpls-tp] [PWE3]   Proposal of using GAL for PW

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: mpls-tp-bounces@ietf.org [mailto:mpls-tp-bounces@ietf.org] On Behalf 
Of Thomas D. Nadeau
Sent: Thursday, July 01, 2010 6:31 AM
To: Giles Heron; Luca Martini; Andrew G. (Andy) Malis
Cc: lihan@chinamobile.com; pwe3@ietf.org; HUANG Feng F; mpls-tp@ietf.org
Subject: Re: [mpls-tp] [PWE3] Proposal of using GAL for PW

On 7/1/10 9:22 AM, "Giles Heron" <giles.heron@gmail.com> 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" <tom.nadeau@bt.com> 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" <lmartini@cisco.com> 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
<Feng.f.Huang@alcatel-sbell.com.cn> <
mailto:Feng.f.Huang@alcatel-sbell.com.cn>  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: pwe3-bounces@ietf.org [mailto:pwe3-bounces@ietf.org] On Behalf Of 
Larry
Sent: 2010年6月30日 17:38
To: mpls-tp@ietf.org; pwe3@ietf.org
Cc: lihan@chinamobile.com
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: +86 10 63601087
MOBILE: 13501093385
********************************************************************

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