RE: [Diffserv-interest] RE: [Diffserv] [OFFLIST] MPLS+Diffserv(ma pping DSCP to EXP)
Shahram Davari <Shahram_Davari@pmc-sierra.com> Wed, 05 February 2003 16:49 UTC
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From: Shahram Davari <Shahram_Davari@pmc-sierra.com>
To: 'Brian E Carpenter' <brian@hursley.ibm.com>, Jeff Norman <jnorman@nortelnetworks.com>
Cc: 'Mark Duffy' <mduffy@quarrytech.com>, nerdboy@rediffmail.com, diffserv-interest@ietf.org
Subject: RE: [Diffserv-interest] RE: [Diffserv] [OFFLIST] MPLS+Diffserv(ma pping DSCP to EXP)
Date: Wed, 05 Feb 2003 07:20:19 -0800
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Brian, > -----Original Message----- > From: Brian E Carpenter [mailto:brian@hursley.ibm.com] > Sent: Wednesday, February 05, 2003 2:57 AM > To: Jeff Norman > Cc: Shahram Davari; 'Mark Duffy'; nerdboy@rediffmail.com; > diffserv-interest@ietf.org > Subject: Re: [Diffserv-interest] RE: [Diffserv] [OFFLIST] > MPLS+Diffserv(mapping DSCP to EXP) > > > Please remove the cc to the diffserv list, since this fits best > on diffserv-interest. > > I don't think loss of info is a tragedy. All this says is that > QOS granularity of MPLS is coarser than the QOS granularity > of diffserv. I disagree with you here. In case of configured E-LSPs you are correct, but in case one uses signaled E-LSPs you could in fact support all 64 PHBs using 8 parallel LSPs. Yours, -Shahram When the IP packets leave the MPLS domain, they > will still carry their DSCP and can receive diffserv treatment > in the downstream IP domain. The fact that several diffserv > aggregates may be mixed on a single LSP is no worse than them being > mixed on a leased line, which is the standard diffserv model. > > (In other words, an LSP is a level 2 as far as diffserv is concerned, > and diffserv is designed to work over any level 2.) > > Also, you don't need 64 mappings in practice. A given diffserv domain > will only have a few PHBs in use; 8 DSCPs active in one domain > (including default) would be a lot, in my view. (OK, there are people > who imagine much more complexity, but that leads to a management > nightmare.) So it doesn't really matter if the solution to > support 64 mappings is clumsy. > > Brian > > Jeff Norman wrote: > > > > 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 > _______________________________________________ Diffserv-interest mailing list Diffserv-interest@ietf.org https://www1.ietf.org/mailman/listinfo/diffserv-interest
- RE: [Diffserv-interest] RE: [Diffserv] [OFFLIST] … Shahram Davari