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RTP vrs RTCP for QoS purposes

I'm studying for the QoS exam and not clear on something ...

I understand that RTP (Realtime Transport Protocol) is used for voice payload and the RTCP (Realtime Transport Control Protocol) is therefore (I presume) the corresponding voice signaling control protocol.

Here's me issue...

In one of my books I see an access list like this:

ip access-list extended AutoQoS-VoIP-RTCP

permit udp any any range 16384 32767

This access list is supposed to match signaling traffic for QoS segregation purposes.

This books also states that RTP uses even numbered UDP ports 16384 - 32767 and that RTCP uses the odd number UDP ports from 16385 - 32767.

Seems to me that the access list above would match both the RTP voice and the RTCP signaling traffic and therefore could not be used to differentiate between the two for QoS purposes. What am I not seeing here?

Thanks in advance for any assistance!

P.S. In the same example RTP audio is matched using the command "match protocol rtp audio".


Re: RTP vrs RTCP for QoS purposes