[c-nsp] ATM QOS

[Dan Martin]

Fix things that are broken, figure out what utilization is like on the
WAN and if its tending up.  look into the composition of that traffic as
well, what percentage are broadcasts?  Is voice getting starved?  If you
get a baseline now, you'll know if what you do next has made any
difference.  

You should also get a trend over some time and try not to leave out the
busy day of the week, the month or the quarter.

Theoretically, having LANE on a wan violates the route to manage
bandwidth and route to manage broadcasts rules.  Taking LANE off the WAN
could make your utilization less subject to the vagaries of broadcasts
and keep you from having to set up a qos infrastructure.  look into
classical IP as a replacement for LANE, assuming your router can route
as fast as your switch can switch.  if you've got some wheezy old
router, don't bother.  On the other hand, if you've got some wheezy old
lane card, don't worry.

You may also consider, assuming its Ethernet, building a point to point
bridge using rfc1483 for your pbx system.  This depends on where your
pbx is and where your atm handoff is and what is between.

I'm assuming that you explored both those alternatives and that is why
you're asking this question.

You may try a pbx to vlan to SPVC with a CBR / low cdvt contract.

If that won't go, you need to figure out how to distinguish the pbx
traffic from the other traffic and color it.  then you need some policy
based routing, then a classical ip instance with that SPVC contract I
mentioned up above.

Hth.







-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Nassess, George
(Contractor)
Sent: Monday, October 03, 2005 2:54 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] ATM QOS

Hello, 
 
I posted part of this question a while ago but no hits. Since I
understand better and can describe it better, I figured I'd try again. 
 
I have a large multisite ATM network running across two metropolitan
BLSR Sonet rings connected by a long haul BLSR sonet ring in between to
create one large ATM network. I need to setup end-to-end QOS initially
between two of many sites on the ATM network to support IP Trunking
between PBXs at different sites for failover and overflow of voice
traffic. Eventually QOS will need to be end-to-end for all sites, and
eventually we will probably get rid of ATM alltogether and just use all
switched optical links.  
 
I have Site A that needs QOS to site C. Sites A,B, and C all connect to
their local ATM switch with an OC3 Interface. Site C and site B have ATM
switches connected by an OC3 link. Site B and Site A have ATM switches
that are only connected by a DS3 link.
 
So this DS3 is a bottleneck for this traffic. I can create a service
policy to prioritize and police traffic as it is put onto the ATM
network, but I have not been able to determine how (and Cisco TAC has
not been able to advise how) to get the ATM switch network to see some
type of marking and apply some sort of priorty queueing or other QOS
mechanism to avoid congestion for our voice traffic from site A to C
without being impacted by any heavy traffic between site A and B. 
 
For our offices that run LANE I can place the appropriate traffic into a
UBR+ queue to prioritize, but noone can seem to be able to explain how
to use any similar mechanism for traffic placed onto the ATM network by
a routed interface that will be honored further downstream on the ATM. 
 
 
Thanks in advance for any assistance, 
 
Gus Nasses
Network Analyst
 
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