Cell Relay Archive

[Scott Brim <swb@newbridge.com>]

(via both e-mail and news)

You have a couple issues, obviously.  First, you want interworking of IP
QoS and ATM QoS (and maybe 802.1D (nee 802.1p) QoS).  We (Newbridge) do
this, and as far as I know everyone who sells equipment at the IP/ATM
interface can do at least rudimentary mappings from IP flows to some ATM
VC parameters.  Also as far as I know the only diff-serv support out
there so far is support for the old TOS bit uses, grandfathered into
diff-serv.

Second you want to communicate application needs at the network
boundaries.  You say you have ATM network control at the connection
points between your LANs and the ATM WAN, so you're not talking about
direct ATM interfaces on your workstations.  In that case, call setup is
done at the gateway.  The application doesn't need to do call setup --
it can't -- rather, it needs to make sure its requirements are met when
it sends packets.  Configured rules, in the gateways, will get you
pretty far -- e.g. a rule saying that traffic going to UDP port x gets
treatment y.  However, applications like H.323 do dynamic port
assignment, so in the long run you need signaling from the end system to
something, to install dynamic rules in the gateways.  RSVP isn't very
appropriate for this.  The children of RSVP that are emerging are more
oriented toward this sort of "client to edge" signaling.  They aren't
ready yet.  Watch the RAP and Diff-serv working groups for interesting
developments.  In the meantime RSVP is what you get.  If you're lucky
you'll find boxes which will map granted RSVP requests into ATM QoS
differences.  We don't do this -- we're supporting configured rules and
good management while waiting for the better protocols.  (When others
claim they do map RSVP to ATM QoS, take a good look and see exactly what
they do.)  So, in summary, configured rules can do a lot for you, and a
number of vendors support them, and they may be all you need for now,
although in the long run you'll definitely need more.

...Scott