Subject: Establishing E / L- LSPs with Bandwidth Reservation

From: "sumit singh" <[email-masked]>
Date: 27 Aug 2003 09:03:11 -0000

Hello,

I have some questions in the RFC 3270 - MPLS Support of 
Differentiated Services.

What does establishing an E or L LSP with bandwidth(BW) 
reservation mean? Does it mean that the BW that has been 
'reserved', for say an L-LSP should be subtracted from the 
corresponding PSC's BW pool before performing the admission 
control for another L LSP with BW reservation request for the same 
PSC?

For example, assume a link with 10 Mbps BW reserved for a certain 
PSC. Now a request comes for a L LSP with required BW reservation 
of 5 Mbps and is admitted. Now if another L LSP request comes with 
the same PSC, and BW requirement of 7 Mbps, should I reject the 
request or accept it? (considering that I cannot adjust the queue 
weights dynamically)?

Also, what does reserving BW for an E LSP request (with multiple 
PSCs) mean? Should I then subtract the LSP's required BW from the 
total BW of the related PSCs, if I accept this LSP request? If 
yes, then how should one decide from which of the corresponding 
PSCs' BW one should subtract the BW required for that E LSP?

Please help me understand.

Regards,
Sumit

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From: Sasha Vainshtein <[email-masked]>
Date: Thu, 28 Aug 2003 20:33:05 +0200

Sharam and all,
Please see inline.

With best regards,
                                   Sasha Vainshtein
email:     [email-masked] <mailto:[email-masked]> 
tel:       +972-3-7659993 (office)
           +972-8-9254948 (res.)
           +972-58-674833 (cell.)

> -----Original Message-----
> From: Shahram Davari [mailto:[email-masked]]
> Sent: Thursday, August 28, 2003 4:47 PM
> To: 'sumit singh'; [email-masked]
> Cc: [email-masked]; [email-masked]
> Subject: RE: Establishing E / L- LSPs with Bandwidth Reservation 
... snipped ...
>  
> >If yes, then how should one decide from which of the corresponding 
> You can't. But this mode should only be used when you don't need to
> differentiate between the BW of different PSCs in the E-LSP. 
> For example when the E-LSP carries AF1x and AF2x.
> 
I do not remember such a recommendation in RFC 3270 (did I miss it?), 
but it definitely looks like the right thing to do.
If it is really missing in 3270, it's a pity since this is quite an 
important issue.
> -Shahram

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From: "Francois Le Faucheur (flefauch)" <[email-masked]>
Date: Fri, 29 Aug 2003 08:45:51 +0100

Sasha, Sumit,

>> If it is really missing in 3270, it's a pity since this is quite an 

Details of the operations of bandwidth reservations in the context of
MPLS Diff-Serv are beyond the scope of RFC3270. However, those are
within the scope of "Diff-Serv-aware MPLS Traffic Engineering" (DS-TE)
developed in the TEWG.
In RFC3564 "Requirements for Support of Differentiated Services-aware
MPLS Traffic Engineering", you may be interested in section "1.3 Mapping
of traffic to LSPs" which discusses the options of how "classes of
services" may be split/grouped over L-LSPs/E-LSPs.

Cheers

Francois