RE: TE Requirements Draft - ELSP

["Roberto Mameli (ERI)" <Roberto.Mameli@eri.ericsson.se>]

Hi Francois and all,

I do not completely agree with you. Please see my comments below.

> -----Original Message-----
> From: Francois Le Faucheur [mailto:flefauch@cisco.com]
> Sent: Monday, November 19, 2001 5:49 PM
> To: Choudhury, Sanjaya
> Cc: 'Francois Le Faucheur'; Jim Boyle; TE WG
> Subject: RE: TE Requirements Draft - ELSP
> 
>          - if I want to do aggregate TE in my network, then I 
> would use E-LSPs with as many OAs as I can fit on them. Then I am doing 
> aggregate CSPF and aggregate CAC.

In my opinion there are scenarios in which I want to do aggregate TE in my network, and at the same time I want to perform per-class CSPF and per-class CAC. Let me illustrate this concept through an example. Imagine 4 nodes A, B, C and D:

                +---+
    +-----------+ C +-----------+
    |           +---+           |
  +-+-+                       +-+-+
--+ A |                       | B +--
  +-+-+                       +-+-+
    |           +---+           |
    +-----------+ D +-----------+
                +---+

Each of the four links (AC, AD, CB, DB) can support a total traffic of 100Mb/s (up to 50 Mb/s of EF traffic and the remaining amount for BE). Now imagine that at a given moment in time the link occupancy is the following:

	Link AC: EF=20Mb/s, BE=40Mb/s (40Mb/s free, 30Mb/s of which available for EF)
	Link CB: EF=20Mb/s, BE=40Mb/s (40Mb/s free, 30Mb/s of which available for EF)
	Link AD: EF=45Mb/s, BE=15Mb/s (40Mb/s free, 5Mb/s of which available for EF)
	Link DB: EF=45Mb/s, BE=15Mb/s (40Mb/s free, 5Mb/s of which available for EF)

Now imagine that you want to set up an E-LSP from A to B requesting 20Mb/s of total bandwidth (10Mb/s for EF and 10Mb/s for BE). You can route it through C, but you can't do the same through D. This is a case in which I think that per-class CSPF and per-class CAC are useful even in the case of E-LSP.
In my opinion the service provider should be free to choose between setting up 2 L-LSPs (or two E-LSP carrying a single OA) or setting up just one carrying both classes. In the latter case the standard shouldn't artificialy limit its traffic engineering capabilities. As a pointed in my previous mail, the only piece we have to add in order to support this scenario is the possibility to signal per-PSC bandwidth requirements.

Regards
Roberto