Subject: Regarding the DiffServ-TE drafts(lefaucheur,boyel,kompella,ash,bi tar)

From: "Choudhury, Sanjaya" <[email-masked]>
Date: Thu, 6 Sep 2001 16:18:34 -0400

Hi! I Now there are 4 different documented approaches related 
	to support of DiffServ-TE by IGPs (lefaucheur,boyel,kompella,
	ash,bitar). As far as I know, the last round of discussion on this
	issue, ended without any consensus. I thought it may not be 
	bad idea to have another round of discussion.

	In my opinion, we can broadly divide the discussions into
	two areas: 
		(a) Whether (and How) to advertise the per-class(/type)
		bandwidth information via IGPs
		(b) Pre-emption

	To limit the scope of discussion, in this thread, let us discuss 
	the first issue only.

	Here are some of my observations and thoughts (If my observations
	from existing drafts are incorrect please correct me).
	
	Your coments will be appreciated.

	Thanks,
	sanjay

	Q1. Do we need to advertise the per-class (/type) bandwidth
	information via IGP ?
	
	 -As far as I understand, two of the drafts  (ash,boyel?) prefer
	 not to advertise per-class bandwidth info for scalability reasons.

	-In my opinion, it is better to advertise the per-class bandwidth
	info via IGP. This information, will help the path computation 
	module to do a better job. And one can handle, the scalability
	problems, via different mechanisms (as illustrated by other 
	drafts). 
		
	Q2. If we need to advertise the per-class(/type) bandwidth 
	information, Should the domain administrator have control
	over the granularity of the information get advertised in his
	domain. ?

	-In my opinion, the domain administrator should have control 
	the per-class BW info that gets advertised in his domain via 
	a MIB (bandwidths for classes that are not advertised can be
	folded into the un-reserved bandwidth associated with the link)

	Q3. How do we advertise the per-class(/type) bandwidth info?
		(a) 1-1 mapping with diffserv classes
		(b) m-1 mapping with diffserv classes (lefaucheur)

	-In my opinion, 1-1 mapping is simpler and achieves the purpose
	without introducing new concepts (class-type).
	-1-1 mapping
		-one of the drafts (bitar) explicitly advertises the BW 
		associated with the class

		-the other draft(kompella) overloads the diffserv-class
		with the priority information.
		
		-which approach is better ?

	Thanks,
	sanjay

---

From: Geoff Huston <[email-masked]>
Date: Fri, 07 Sep 2001 20:26:10 +1000

At 9/7/01 06:18 AM, Choudhury, Sanjaya wrote:

>    drafts)

This is a critical issue, as the scaleability concerns regarding the number 
of updates of per class bandwidth information may get quite significant. 
Which drafts are you referring to that address the scaleability issues?

thanks

   Geoff