RE: More comments/questions on DS-TE solution draft

["Choudhury, Sanjaya" <Sanjaya.Choudhury@marconi.com>]

Hi Francois! In the second part of your response you
eluded to the "initial" DS-TE solution. I just want
clarify whether you are still pursuing the latest
approach you indicated in your previous e-mail (
around the time of IETF conf). i.e.

	1. In the last e-mail you indicated that you
	are leaning towards the explicit signaling 
	of the ClassType.
	
	2. The e-mail also indicated that the user
	has to explicitly configure the mapping to
	identify the bandwidth to be advertised:
	[ClassType][SetupPriority] 	index-in-available
						adv. TLV
	User is expected to configure only few 
	priorities per ClassType.

	Are you still perusing these approaches in
	your latest rev. of the draft ?

Another unrelated question: As far I understand, the 
available bandwidth will get advertised periodically. 
Do you think this approach will be sufficient for a 
DS-TE network, with lot of LSPs being created and 
deleted?

Thanks,
sanjay

> -----Original Message-----
> From: Francois Le Faucheur [mailto:flefauch@cisco.com]
> Sent: Wednesday, January 30, 2002 6:49 AM
> To: Choudhury, Sanjaya
> Cc: 'te-wg@ops.ietf.org'
> Subject: Re: More comments/questions on DS-TE solution draft
> 
> 
> Sanjay,
> 
> thanks again for these comments. It's great to have them 
> ahead of time.
> 
> thoughts on 3 & 4:
> 
> >3. It will be helpful, if the draft spells out any domain 
> level restrictions
> >     /recommendations that the user should keep in mind. For example:
> >         a) Is it necessary for the number of CTs to be same in
> >         all the links of all LSRs in the DS-TE domain ?
> >         b) Does the CT identifier have to be consecutive in nature ?
> >         c) Is it necessary that _all_ the LSRs in the domain MUST
> >         support DS-TE.
> >             if it is not necessary then :
> >                 i) What should be the behavior if a LSR that
> >                 does not support the signaled (or inferred) CT ?
> >
> >4. How can a LSR distinguish between the DS-TE and non DS-TE
> >     bandwidth advertisement (DS-TE re-uses the existing constructs
> >     to advertise the available bw in a CT+priority basis) ?
> 
> The working version of the draft indicates that:
>          - to use more than one CT anywhere in the network, 
> all LSRs must 
> support DS-TE (an LSR can not distinguish through signaling 
> whether an IGP 
> advertisement is for TE or DS-TE)
>          - all LSRs must support the same BAndwidth Constraint Model
>          - all LSRs must be configured with the same 
> CT/Preemption mapping 
> (this is defined more precisely in the draft, but basically 
> it indicates 
> which CT/Preemption is advertised in each Bw value of IGP).
> 
> This approach results from earlier discussion. You would 
> remember that our 
> initial "solution" proposed that we advertise  a Bw value for 
> up to (8 
> preemption) times (8 CTs). One of the main motivations for 
> doing so was so 
> that an LSR can automatically detect which other LSR is 
> TE-only or DS-TE 
> capable and so that you could set-up LSPs from other CTs than 
> CT0 around 
> TE-only LSRs.  Another motivation was that no consistent 
> mapping needed to 
> be configured since each value was explicitely associated 
> with a given 
> preemption and CT inside the IGP advertisement . After a lot 
> of discussion 
> (including input from SPs), the conclusion was that these 
> operational/configuration benefits did NOT justify extra IGP 
> signaling and 
> associated scalability impacts. So the decision to advertise 
> only 8 bw 
> values included the assumption that things need to be upgraded and 
> configured in a consistent fashion. Note that this is 
> generally in line 
> with Diff-Serv anyway where things must be configured 
> consistently on all 
> boxes.
> 
> Cheers
> 
> Francois
> 
> >Thanks,
> >sanjay
> >
> >
> >
> >
> 
> 
> _________________________________________________________
> Francois Le Faucheur
> Development Engineer, IOS Layer 3 Services
> Cisco Systems
> Office Phone:          +33 4 97 23 26 19
> Mobile :               +33 6 19 98 50 90
> Fax:                   +33 4 97 23 26 26
> Email:                 flefauch@cisco.com
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> 
> 


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