The MPLS WG Archive

[Francois Le Faucheur <flefauch@cisco.com>]

Lou,

At 09:49 27/07/2000 -0400, Lou Berger wrote:
>Francois,
>
>At 05:45 PM 7/26/00 +0200, Francois Le Faucheur wrote:
>>Lou,
>>
>>At 12:04 24/07/2000 -0400, Lou Berger wrote:
>>
>> >
>> >How about including an "SHOULD" level option that allows a MPLS-DS LSR to
>> >treat LSPs signaled without the DIFFSERV object as non-DS LSPs?  I think
>> >this would address this issue.
>> >
>>
>>Just to be sure I understand the proposal:
>>The text would say that when there is RSVP signaling without the Diff-Serv 
>>object, the LSR SHOULD (instead of MUST) interpret this as a request for 
>>an "E-LSP using Preconfigured EXP<-->PHB Mapping".
>>(which would imply that if there's a really good reason to do otherwise - 
>>eg. to maintain some pre-Diff-Ext QoS support - then you could do so).
>>
>>If that's the proposal, that works for me.
>
>On additional recommendation and we're there. Something like:
>An implementation SHOULD include an option that overrides this.  When this 
>"override option" is set, the LSR then treats LSPs signaled without the 
>DiffServ object as standard, non-DS, LSPs.
>
>How does something like this sound?
>

But what exactly is a "standard, non-DS, LSP"?:
	- an LSP which has no QoS?
	- an LSP which has an Int-Serv CL/GS service. And then, are EXP bits igored?
	- an LSP which has some Diff-SErv service based on a non-zero-COS-field as per the scenario you mentioned earlier? And then , are EXP bits ignored?
	- any of the above?
My perception is that this is quite open and we shouldn't have to worry about it in the Diff-SErv spec. We have agreed on an "escape code" above (the first "SHOULD") which allows one to maintain whatever flavor of "standard, non-DS, LSP" he/she liked. I think this is all the Diff-Serv spec probably needs to say and would prefer to avoid having to mention in any way QoS support which were pre-Diff-Ext. So I'd like to leave out the new recommendation.

In any case, if a statement about Override option was to be included, I would argue that it should be a MAY and not a MUST. I think it is quite reasonable for a new implementation supporting MPLS Diff-SErv "a la" Diff-Ext to not worry about pre-Diff-Ext stuff.

Thanks

FRancois
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Francois Le Faucheur   
Development Engineer, IOS Layer 3 Services 
Cisco Systems 
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