Can queue size of a priority queue affect latency/jitter?

[Seth Beauchamp]

Meaning if I use "priority percent 80" when I really only need 30%, does that have any negative affect? Is it best practice to use the smallest possible number (maybe 35 or 40 in this example) for a PQ to keep latency and jitter at its lowest? I saw a recommendation elsewhere to keep the queue size low for the best latency/jitter results, so I was curious if this was true. I couldn't find any specific cisco docs stating either way.

[Philip D'Ath · Accepted solution]

Well, I guess you could make the priority queue huge.  The impacts would be if traffic in the priority queue was much larger than expected (say something goes wrong) it will starve other traffic.  Also by allocating 80% to one class you don't leave much to give other classes.

Typically you would make it the size of the expected traffic plus sometimes a little bit more for head room.

For example, if you wanted to support 4 concurrent 96Kb/s streams (being 64Kb/s for codec and 32Kb/s for the IP overhead) you would make it around 384Kb/s.