QoS funfacts

Hello

A few things we tend to forget when setting up QoS on routers:

1. it is a good idea to decrease the tx-ring buffer (hardware queue) to the minimum size so that we have more control over the traffic in the software queue
2. IOS considers congestion to be occurring when the hardware queue is full
3. This means that we might have e.g. a 100mbit link, but with tx-ring decreased even small load will cause the router to believe there is congestion on the link. This means that our QoS output policy will kick in (good!)
4. It is a good idea to always assign bandwidth to the class-default, otherwise unused bandwidth will be split across all configured classes.
5. It is a bad idea to have one priority queue for voip + video traffic