RE: [RPRWG] Frame reordering for medium priority traffic in Ganda lf?
Turner,
At 04:35 PM 12/21/2001 -0500, Turner, Gary (Gary) wrote:
>Mike, Anoop, Jim,
>
>Unfortunately, the revised text still says:
>
>"However the priority class on the ring transit
>path will be different depending on whether the
>particular frame is in or out of its agreed
>CIR/EIR/BIR profile."
>
>This would still lead to misordering.
>
>Looking at other parts of the proposal, in particular
>the flowchart of Fig. 12 on page 39 I think the profile
>conformance only affects access to the ring: during
>the time of conformance Med packets are added just
>behind Hi packets in priority, but during the time of
>nonconformance they are added subject to the
>fairness algorithm, just ahead of Lo traffic.
>
>Once on the ring Med traffic always occupies the Lo
>transit queue.
>
>Is this correct?
This is correct.
Thank you for pointing out the inconsistence which we will
correct in our next version draft.
Regards,
Jim
>Thanks,
>
>Gary Turner
>
>
> > ----------
> > From: Anoop Ghanwani[SMTP:anoop@xxxxxxxxxxxxxx]
> > Sent: Friday, December 07, 2001 1:01 AM
> > To: 'Mike Takefman '; Anoop Ghanwani
> > Cc: 'stds-802-17@xxxxxxxx '
> > Subject: RE: [RPRWG] Frame reordering for medium priority traffic in
> > Ganda lf?
> >
> >
> >
> > Mike,
> >
> > And in fact the pre-Gandalf proposal did actually state
> > things the way you explain below. That's what confused
> > me. Thanks for the clarification.
> >
> > -Anoop
> >
> > -----Original Message-----
> > From: Mike Takefman
> > To: Anoop Ghanwani
> > Cc: stds-802-17@xxxxxxxx
> > Sent: 12/6/01 8:24 PM
> > Subject: Re: [RPRWG] Frame reordering for medium priority traffic in
> > Gandalf?
> >
> > Anoop,
> >
> > We discovered this error in the document soon after the meeting.
> > Our presentations have consistently stated that the medium
> > priority class is treated as high priority only from the
> > perspective of admission, not transit. Clearly, we missed it
> > in our review of the document prior to the meeting.
> >
> > thank you for raising the issue,
> >
> > mike
> >
> > Anoop Ghanwani wrote:
> > >
> > > In Section 2.2.2 of the Gandalf proposal, we have the following
> > > statement:
> > > "However the priority class on the ring transit path will be
> > > different depending on whether the particular frame is in or
> > > out of its agreed CIR/EIR/BIR profile. In-profile frame will
> > > be delivered on the high priority low-delay transit path while
> > > out-of-profile traffic will transit on the low-priority,
> > > best-effort path."
> > >
> > > This seems to suggest that frames belonging to the medium
> > > priority class of traffic can get reordered since a later
> > > frame that is determined to be in-profile may get to
> > > the destination node before an earlier one that was
> > > determined to be out-of-profile.
> > >
> > > It's well known that protocols such as TCP will suffer
> > > throughput degradation if packets are reordered, and
> > > therefore most protocols (such as, for example, 802.3ad
> > > link aggregation) make every effort to ensure that frames
> > > are delivered to the destination in order. Is there a
> > > reason why re-ordering has been considered acceptable in
> > > this case?
> > >
> > > This issue may have already been brought up at the meeting,
> > > but if it was then I missed it. (I must've been at one
> > > of them bridging sessions. :-)).
> > >
> > > -Anoop
> >
> > --
> > Michael Takefman tak@xxxxxxxxx
> > Manager of Engineering, Cisco Systems
> > Chair IEEE 802.17 Stds WG
> > 2000 Innovation Dr, Ottawa, Canada, K2K 3E8
> > voice: 613-254-3399 fax: 613-254-4867
> >