Hi Mikael,
I can't find reference to DSCP 000010 or 000110, where are they defined?
I know the title 'assured forwarding' seems to imply better than best
effort, but I think this is a mistake for AF1 - which seems to be
recommended for bulk traffic that is not latency sensitive. You can't
make everything high priority! I believe AF1 according to the list of
recommended applications, would be better served at less than best
effort priority - so the 4 queue 1a mapping based on the top 3 bits of
the TOS byte would be OK. AF2 -> lower than best effort would be wrong
however.
Simon
On 5/13/2015 1:47 AM, Mikael Abrahamsson wrote:
On Tue, 12 May 2015, Simon Barber wrote:
Hi John,
Where would be the best place to see if it would be possible to get
agreement on a global low priority DSCP?
Currently the general assumption among ISPs is that DSCP should be
zeroed between ISPs unless there is a commercial agreement saying that
it shouldn't. This is generally accepted (there are NANOG mailing list
threads on several occasions in the past 5-10 years where this was the
outcome).
The problem is quite complex if you actually want things to act on
this DSCP value, as there are devices with default behaviour is 4
queue 802.1p, with 1 and 2 (which will match AF1x and AF2x) will have
lower priority than 0 and 3 (BE and AF3x), and people doing DSCP based
forwarding, usually does things the other way around.
It might be possible to get the last DSCP bits to map into this,
because for DSCP-ignorant quipment, this would still be standard BE to
something only looking at CSx (precedence), but that would be lower
than 000000. So DSCP 000110 (high drop BE) might work, because it's
incremental. Possibly DSCP 000010 (low drop BE) might be able to get
some agreement because it doesn't really cause any problems in the
existing networks (most likely) and it could be enabled incrementally.
I would suggest bringing this kind of proposal to operator
organizations and the IETF. It needs to get sold to the ISPs mostly,
because in this aspect the IETF decision will mostly be empty
hand-waving unless the operators do something.
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