Subject: RE: MPLS Diffserv

From: Shahram Davari <[email-masked]>
Date: Mon, 9 Apr 2001 12:07:44 -0700

Hi,

Unfortunately not. Because to identify the PHB of an MPLS packet you need to look at its 4 byte MPLS label stack entry (20 bit label, 3 bit EXP, 1 bit stack, 8 bits TTL). If you don't want to consume MPLS label, then you are have to use 3-bits from TTL-field. I doubt anybody wants to change the semantics of TTL field (=> no backward compatibility).

Yours,
-Shahram

> -----Original Message-----
> From: N S S Kishore Kankipati [mailto:[email-masked]]
> Sent: Monday, April 09, 2001 11:46 AM
> To: Shahram Davari
> Cc: [email-masked]
> Subject: MPLS Diffserv
> 
> 
> hi all
> 
> DSCP contains 6 bits. Therefore number of PHBs
> possible
> is 64 (including default PHB). If an LSR has to
> support all PHBs it requires at least 8 E-LSPs. If
> only L-LSPs are used, it requires more than this. If
> we use both the types of LSPs, the number of LSPs
> required may be intermediate to the previous two
> cases. 
> From this we can infer that for every FEC it requires
> at least 8 LSPs. A LSR may contain more number of FECs
> and in that case number of LSPs (and labels)required
> is very large. 
> Isn't there any way to reduce number of LSPs and
> conserve label space in that case(LSR has to support
> all PHBs possible)?
> 
> regards
> kk
> 
> 
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