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Community Member

qos catalyst 4500 7E supervisor

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

5 REPLIES
Hall of Fame Super Bronze

qos catalyst 4500 7E supervisor

The line rate.

Community Member

qos catalyst 4500 7E supervisor

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

Hall of Fame Super Bronze

qos catalyst 4500 7E supervisor

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.

Community Member

qos catalyst 4500 7E supervisor

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

Hall of Fame Super Bronze

qos catalyst 4500 7E supervisor

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.

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