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

[Giles Heron <[e-mail]>]

I’m all up for narrowing it down.  But then the question is what do we
narrow down to?  For the future GAL might be a better option than CW (at
least in the TP case where we don’t have to worry about ECMP etc.)

On 01/07/2010 14:31, "Tom Nadeau" <[e-mail]> wrote:

> 
> 
> 
> 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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>>>>>   
>>>> 
>>>> 
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