Re: [tsvwg] I-D Action: draft-svshah-tsvwg-lln-diffserv-recommendations-04.txt

[Brian E Carpenter <[e-mail]>]

> 
> 4.2.1. Deterministic Control Signals
> 
> 
>    PHB for this class of traffic is defined as forwarding of a packet at
>    determined/scheduled time providing no jitter service.
> 
>    Recommended DSCP code-point for this class of traffic is EF.  Since
>    this class of traffic is not expected to co-exist with voice like
>    traffic, that implements EF code-point as used in traditional Campus
>    and WAN networks, the same code-point is re-used here for the purpose
>    of deterministic control signals.  However, a note to be made for
>    defined PHB for this code-point as deterministic forwarding behavior
>    as defined in this document.
> 
>    Scheduling MUST pre-empt service of any other class of traffic during
>    the scheduled time for this class of traffic.

I am confused. This seems to have nothing to do with EF; in fact
it violates the definition of EF, which certainly does not allow
for absolute pre-emption (or "no jitter", which is physically impossible).

It seems closer to CS7 than anything else. But if you are asking for
absolute preemption, it's a new PHB that is not defined anywhere
today. (Dropping the reference to draft-svshah-tsvwg-deterministic-forwarding
makes no difference: in practice the current draft defines a new PHB.)

Any new PHB could in principle be mapped to any DSCP value, such as
the recommended values for EF or CS7, but that doesn't mean it
can be named EF or CS7, because they already have precise meanings.

   Brian