Correct QoS arrangement with a T1 and 10 IP phones


Nov 25, 2008
Greetings all,

I have the following setup:

- A 1.5 Mbps WiMAX symmetric T1 Link
- An Asterisk 1.4.32 server with Elastix 1.6.2-4 x86_64 and 2 NICs:
NIC #1: NIC #2: 74.XXX.XXX.89
- A Linksys Cisco RV042 Dual Wan Router
- A public network configured on the DMZ Port of the router.
- Voice Codec: G711u (u-law)

My idea is to prioritize the traffic for all IP phones no matter what is happening with the internet service (People downloading large e-mails, watching streaming videos on youtube, and so on)

For that purpose, I am considering that all phones will have enough bandwidth to handle 2 calls at the same time, both outgoing calls, both incoming calls or one incomi ng, one outgoing. Also, according to my statistics, just 5 out of the 10 persons could be making or receiving calls simultaneously.

Considering that every G711u call will use 90Kbps for upstream and downstream bandwidth and all phones are connecting to the PBX's private IP even when the outgoing traffic is routed to the public IP 74.XXX.XXX.89 then I would like to know if the settings I have set for my router are correct.

Please find attached to this message my current QoS settings. I also have 4 remote extensions connected to this IP-PBX using ATAs but I have set nothing for them.

Am I doing the right thing? There are times when I experience break ups in the conversations, specially these days where people are watching the FIFA World Cup games on their computers and they also need to answer and make calls.

My doubts basically are:

1) Is it correct to separate bandwidth for each phone's IP and also for the private IP of the IP-PBX? I ask this because it's the public IP address of the PBX the one facing the internet and not the private IP masked with a public IP. As you can see, that is my current setting.

2) Would I rather just separate bandwidth for the IP phones and not the IP-PBX?

3) If #1 and #2 are wrong, please help me decide and choose the right QoS for my VoIP environment.

Thank you all in advance,



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