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RE: DiffServ field

> >Does anyone know is use of DiffServ field supported in some equipment
> >networks?
> It is supported in some equipment. I wouldn't be able to tell you how
> networks configure their equipment; they generally view this as NDA
> information.

We have found some issues when trying to use the diffserv field in
practical deployments. There are a number of routers in the network that
were built and deployed before diffserv was widely accepted as a
standard. Understandably, these routers implement the previous standard,
i.e. the RFC 791 definition of the TOS bit. Specifically, the old
routers look at the three precedence bits and treat it as a priority
level. In practice, this restricts the number of diffserv code points
that can be safely used. You don't want for example to define a code
point for "less than best effort" in which the three precedence bits
happen to mean "high priority" in the old routers...

-- Christian Huitema

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