Need QoS config help on 1841 Adv. Sec.

Unanswered Question
Jun 25th, 2007

I've got two 1841 routers with adv sec IOS connected via a 3Mbps bonded T1 PtP circuit. Both offices have Avaya IP Office systems and I need to implement QoS for VoIP calls between these two offices. There is no "auto qos" on the adv sec image, which is needed for the firewall, vpn, etc., so need help with a (hopefully) basic manual QoS configuration. I'm told RTCP ports to QoS are 49152 to 53246, and not much else. Can anyone point me in the right direction with a config?

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royalblues Mon, 06/25/2007 - 11:02

You can do something like this

class-map match-all voice

match ip rtp 16384 16383

class-map match-all signalling

match ip dscp cs3

policy-map QoS-to-P2P

class voice

priority 1024

class signalling

bandwidth 300

class class-default

fair-queue

Interface multilink 1

Max-reserved-bandwidth 100

service-policy output QoS-to-P2P

HTH, rate if it does

Narayan

mohammedmahmoud Mon, 06/25/2007 - 11:28

Hi,

Just to add a small info about RTP ports, the RTP RFC-1889 stipulates that an even port number be used for the RTP stream and the next subsequent odd port number be used for the corresponding RTCP stream, these ports are in the range 16384 - 32767.

HTH,

Mohammed Mahmoud.

royalblues Mon, 06/25/2007 - 11:38

In case you want the RTP audio as well as the RTCP stream to be prioritised, you can change the class map to

class-map match-all voice

match access-group voice

ip access-list extended voice

permit udp any range 16384 32767

HTH,

Narayan

I strongly recommend you implement DiffServ QoS for voice services.

If you use access lists you run the risk of having non-voice traffic tagged and placed in your Voice Queue.

I am not familiar with the Avaya equipment but I am sure they must have a guide on how to configure a Cisco switch to mark voice packets with the appropriate DSCP marking(normally EF).

Paolo Bevilacqua Tue, 06/26/2007 - 10:56

I agree 100% with bgibson above.

1. make sure your phones mark RTP as EF. Usually this is the default or very easy to configure.

2. In the service policy, match dscp ef.

That's it.

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