[cisco-voip] catalyst policing for voice

[HIERS, DAVID (AIT)]

Hi,
If called upon to police for one voice call on a cat 3550 switchport, what numerical value should be used for the bps?

One authority indicates that this is the right answer:

 police 128000 8000 exceed-action drop
! Only one voice call is permitted per switchport VVLAN

I guess that we can assume 711 codec, as a ton of 729 calls will fit in 128kbps.

What is 128000 good for?  

Two 711 media streams?
Nope, the policer is applied in the inbound sense later in their config.
Anyway, it'd be dumb as the policer can't measure the media stream, it should include the entire L2 frame.  I think some version of code only used the L3 size, tho.

One 711 media stream and a whole lot of overhead?
Maybe, we dang sure can't get two calls thru, and it will allow a ton of overhead.


128000 bps sure seems like an odd number to come up with for "one voice call".

I'd go for something around 92kbps, which is large enough for a single 711 call, plus some L2/3 overhead.

David Hiers

CCIE 10734, CISSP