RE: [Diffserv] [OFFLIST] MPLS+Diffserv(mapping DSCP to EXP)

"Jeff Norman" <jnorman@nortelnetworks.com> Tue, 04 February 2003 22:16 UTC

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From: "Jeff Norman" <jnorman@nortelnetworks.com>
Reply-To: "Jeff Norman" <jnorman@nortelnetworks.com>
Subject: RE: [Diffserv] [OFFLIST] MPLS+Diffserv(mapping DSCP to EXP)
To: Shahram Davari <Shahram_Davari@pmc-sierra.com>
cc: "'Mark Duffy'" <mduffy@quarrytech.com>, nerdboy@rediffmail.com, Diffserv@ietf.org, diffserv-interest@ietf.org
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Shahram,
  You are referring to L-LSPs where a one-to-one mapping can
be done, where as E-LSPs there isn't, which is what I believe
nerdboy is asking about.

Best Regards,
--Jeff

In message "[Diffserv] [OFFLIST] MPLS+Diffserv(mapping DSCP to EXP)", Shahram Davari writes:

>> -----Original Message-----
>> From: Mark Duffy [mailto:mduffy@quarrytech.com]
>> Sent: Tuesday, February 04, 2003 7:29 AM
>> To: nerdboy@rediffmail.com; Diffserv@ietf.org
>
>> >2. Further, since the DSCP  ( pow(2,8) = 256 combinations ) 
>> is 8 bits and
>> >provides 22 different PHB's(or roughly 7 different classes),
>> >      and the EXP is just 3 bits and therefore can provide 
>> only upto 8
>> >different classes, wouldnt there be loss of info while 
>> mapping DSCP->EXP ?
>> >
>
>No because in MPLS we do DSCP=> PHB translation and PHB=> EXP+Label encoding. The label gives you the context info, so each label can support up to 8 PHBs. To support all 64 PHBs (which are not defined yet) you need 8 parallel LSPs.
>
>
>-Shahram
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>
>


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