From: Henning Brauer (lists-openbsdbsws.de)
Date: Thu Aug 23 2007 - 03:26:25 CDT

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* David Newman <dnewmannetworktest.com> [2007-08-23 01:30]:
> >> Also, I noticed today that Google marks all their stuff with a DSCP of
> >> 0x38 (high throughput, low delay). Nice trick, but also an excellent
> >> argument for re-marking capability in all routers.
> >
> > nice trick? rather useless. I'd be extremely surprised if it makes any
> > difference at all.
> > i mean, who is really
> > 1) looking at DSCP/TOS at all,
> > - and -
> > 2) using them for different forward9ng priorities
> > - and -
> > 3) has congestion/fwd capa shortage so that it actually makes a
> > difference,
> > - and -
>
> For various reasons I can't name names, but I can tell you that there
> are some VERY large service provider and enterprise networks using DSCP
> classification and prioritization.

yes, sure, within their networks.

> ISPs tend to run at much higher utilization levels than enterprises and
> congestion is a reality on at least some of their pipes.

i know the ISP market very well, and I have yet to see that. at least
in europe, basically everybody has spare capacity like beer on
weekends.

> And even in the absence of congestion, there's still a desire to service
> delay- and jitter-sensitive voice and video ahead of other traffic.

true. I have my doubts wether all this tos/dscp dance really makes much
of a difference there, but yes, it can help.

> > 4) trusts externally set TOS/DSCP
> No one should trust external TOS or DSCP markings. Again, what Google is
> doing is an excellent argument for re-marking capability in all routers.

yup, i agree.

> And here we come full circle. Given the OpenBSD now IS a router --
> whether it's a little two-interface pf box for home use or some big
> studly hardware running OpenBGPD and OpenOSPFD box for ISPs, I would say
> the addition of support for DSCP re-marking would be a very desirable
> feature.

i'd call it a nice-to-have, yes.

--
Henning Brauer, hbbsws.de, henningopenbsd.org
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