I believe you are wrong. On obvious counter-example comes if the sender
has no privilege with the sender's ISP, but the receiver has these
privileges. In that case, the packet is marked as "priority high,
traffic type X" by the sender; the sender ISP's rewrites that to
"priority standard, traffic type X"; the receiver's ISP rewrites to
"priority high, traffic type X."
By the way, many people seem to believe that diffserv necessarily ties
with monetary exchanges. That is not necessary, if for example you
implement "alternative best effort" and get 2 best effort classes, one
for "high throughput, low loss", and one for "low delay, possible
losses."
-- Christian Huitema
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, August 29, 2001 2:21 PM
> To: Christian Huitema; [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]
> Subject: RE: a), b), c), d), or e)
>
> Christian,
>
> I might be wrong, but it seems that a downstream (operator) router
> CANNOT
> use end-to-end immutable information. If the policer in the 1st
> operators
> domain concludes that the customer is not paying enough for the
> treatment
> he's asking, the "treatment indicator" needs to be downgraded. If that
> is
> not allowed, the only other option would be to drop the packet
> altogether.
>
> Jarno
>
> Christian Huitema wrote:
> > > > There are no stupid questions. Some of the pushback is
> > > > simply based on the fact that the diffserv model of QoS
> > > > is inherently broken because there is no end-to-end
> > > > immutable set of bits for local decisions to be based on.
> > >
> > > This is a very unfair comment. Diffserv is just fine in the
> > > case of unencrypted traffic. It has a problem (and so does
> > > intserv I suspect) with tunnel or transport mode ESP.
> >
> > ESP is just one of the cases in which "looking at the port
> > numbers" does
> > not provide sufficient information to make an informed decision.
> There
> > are many examples that do not involve ESP, e.g. an audio stream can
> > carry different levels of hierarchical encoding on successive
> > ports, an
> > HTTP transaction can carry a medical transaction just as well as
> > recreational content, a file transfer may be a virus update or a
> virus
> > propagation. At some point, the classification decision has to rely
> on
> > information provided by the source.
> >
> > In fact, there is no contradiction between the "immutable"
> requirement
> > that Tony is advocating and Brian's "diffserv handle" requirement.
> In
> > the diffserv model, the actual classification is based on the 6
> > classifier bits; there is no context that this can be mutable, since
> > ISPs must be authorized to reclassify traffic. The reclassification
> is
> > based on information carried in the packet, part of which is the
> label
> > affixed by the source; making that label immutable is a good thing,
> > since it prevents intermediaries from removing the
> > information that can
> > be used by a downstream router.
> >
> > -- Christian Huitema
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