BCN VOIP/QOS Performance issues?

[dsullinger]

We have 3 BCN's as our backbone hub routers. Currently the CPU's are only showing about 10% usage according to Optivity. We are testing the idea of turning on QOS for VOIP and I was woundering if anyone has did this and if so, how did it effect the performance of the router?

BTW - We are running BayRS v13.2 Router Software

 

[Jynxx]

It depends...what type of links are the BCN's connecting to?

If they are connecting via FR or PPP, you will not be able to run QoS on them...at least if they are like ASN's, ARN's, and 2430's. I don't have any BCN's, so you will have to check.

The reason is that if they are configured with any WAN type that uses Protocol Priority by default, you can't set up DSQMS because they are incapable of running 2 seperate dequeuing algorithms. For FR and PPP, at least, Protocol Priority MUST be on. Even though you are not doing anything special with the traffic, throwing everything into the normal queue, there is a hidden queue that resides above the high queue that your FR LMI packets, etc, get inserted in to. If you disable Protocol Priority or turn on DSQMS (which also disables it), it will lose control of the line and start bouncing. Trust me on that one.

 

[Jynxx]

Also, the best way to run QoS over them, at least from my experience, is to front end them with a BPS2000 and run QoS at that point. If they are prioritized as they leave the switch, the router will just FIFO the packets anyway, so it will be fine.

Also note that, from my experience, it appears as though Nortel Routers are actually re-marking high marked traffic as Critical ECP. (You can check it out through the PCAP/TAP interface sniffer)

So if you have anything like Sprint's packet express or iFR keep this in mind, because it will totally hose your QoS design if you have to set the traffic at certain DSCP binary values.

Against all RFC's for QoS I know...