qos catalyst 4500 7E supervisor

[whanson]

I am trying to understand the implicit limit to the priority queue. I know you can define an explicit policer but if you don't I can't find out what the rate limit really is.  thx again

[Edison Ortiz]

The line rate.

[whanson]

Not sure I understand that if the priority is line rate yet you can specify bandwidth remaining for other classes how would there ever be any left

[Edison Ortiz]

If you are sending line rate speed priority flows, it will use 100% of the link hence the recommendation for placing policers along with the priority command to avoid other flows being discarded.

Other platforms have the ability to allocate a value to the priority queue which in turn is an implicit policer.

[whanson]

but the documentation indicates that is you don't have a policer you can use bandwidth remaining

so

policy-map

class voice

priority

class whatever

bandwidth remaining  percent 10

how can there be anything remaining if the priority takes up 100% of the available

thx

[Edison Ortiz]

If you sent 100% priority traffic, there won't be remaining bandwidth guaranteed hence the 10% is null.

If you sent 90% priority traffic, then 10% will be guaranteed.

In very rare occasions, you will see priority using 100% of the traffic but it could happen due to misconfiguration

(i.e. assign priority class to high bandwidth flows).

Voice bearer, the default priority flow, does not demand a lot of bandwidth.