Subject: draft-ietf-tewg-diff-te-reqts-06.txt

From: "Ting Chung" <[email-masked]>
Date: Fri, 31 Jan 2003 10:59:47 -0500

As a service provider, we have looked at the DiffServ-TE (DS-TE) feature for 
awhile now. Back then, we are still struggling to find an application for 
these features, especially if we just confine ourselves to the Internet 
world of traffic which are mostly connectionless and best effort in nature. 
With the recent push of L2 over MPLS technologies, and our intention to 
utilize these L2 over MPLS technologies to reduce our wide area transport 
cost, we find the DS-TE can help us quite a lot during implementation of 
these plans.
In the normal IP world, traffic is connectionless in nature and packets 
transiting through the network does not usually have a fixed path. However, 
when tunneling L2 (in particular ATM) traffic over our MPLS backbone, the 
DS-TE can be used as a CAC-like mechanism to ensure the the LSP bandwidth 
that we are reserving through the network is being accounted for properly on 
the hopto-hop bases. For example, the bandwidth constraint concept 
introduced in the DS-TE can be used to ensure the amount reserved CBR type 
of LSP's does not exceed a certain percentage of the total link bandwidth. 
By setting up different LSP's for different classes of ATM traffic (CBR, VBR 
and UBR, etc.), the corresponding composition of the different classes of 
traffic and their respective overbooking ratio can be better managed and 
accounted for. Although this may be only a coarse way to simulate the 
traditional ATM CAC mechanism, but this can help to secure our first step 
towards ATM over MPLS implementation. In Canada, long haul bandwidth is 
still an expensive asset and the ability to overbook these long haul links 
by consolidating all the layer 2 and layer 3 services onto them and turning 
on QoS to differentiate the different types of traffic classes is crucial in 
helping us to lower our cost.

I therefore believe that it is worth spending efforts to further develop the 
DS-TE concepts and protocols.

Ting Wo Chung
Senior Network Architect, IP Technology, Bell Canada
181 Bay Street, Suite 350, Toronto, Canada, M5J2T3

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