Subject: RE: Establishing E / L- LSPs with Bandwidth Reservation

From: Shahram Davari <[email-masked]>
Date: Thu, 28 Aug 2003 07:46:58 -0700

Hi Sumit,

>-----Original Message-----
>From: sumit singh [mailto:[email-masked]]
>Sent: Wednesday, August 27, 2003 5:03 AM
>To: [email-masked]
>Cc: [email-masked]; [email-masked]
>Subject: Establishing E / L- LSPs with Bandwidth Reservation 
>
>
>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?

Yes, correct.

>
>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)?

The second L-LSP will be rejected unless its traffic is reduced
a rate that is < 5 Mbps (for example by sending some portion of the traffic over another L-LSP).

>
>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?

Yes.
 
>If yes, then how should one decide from which of the corresponding 
>PSCs' BW one should subtract the BW required for that E LSP?

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.

-Shahram

>
>Please help me understand.
>
>Regards,
>Sumit
>
>
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---

From: Keith Knightson <[email-masked]>
Date: Fri, 29 Aug 2003 11:27:49 -0400

Sharam,

Is there a definition of bandwidth?

Does  X mbit/s mean X mbit/s continuous sustained bandwidth for ever?

Measured over what duration, and at which time.

Guaranteed under certain conditions? What conditions?

If an allocated "pipe" is idle, it must always remain idle in the 
face of a new demand?

Can bandwidths really be simply added together, as if they were real 
physical pipes?

Regards

Keith