[cisco-voip] SIlly QoS Question

[Jonathan Charles]

[cross-posting to Puck and the CCIE Online Study List...if you guys
aren't familiar with each other, you should be...]


Ok, so Cisco is migrating control traffic from AF31 to CS3...

I am curious as to why... the QoS SRND says they are moving to CS3
"because Class Selector code points, as defined in RFC 2474, were not
subject to markdown/aggressive dropping"

OK, I guess...

But.

WRED is enabled on each non-priority queue on the Cisco 3550 (queues
1,2 and 3)...

Doesn't the lack of any drop thresholds (low, medium and high) in the
CSX PHB levels, cause this traffic to be potentially dumped in the
case of congestion?

In other words, since AF31 has a binary value of 011010 and CS3 has a
binary value of 011000, that means that CS3 has nothing set for Delay,
Throughput or Reliability; whereas AF31 had high throughput set.

How is CS3 better?



Jonathan