QoS On Netvanta 1335 for Hosted SIP PBX

[Anonymous]

We have a Netvanta 1335 we want to use with a hosted SIP provider and a Comcast Business Internet Connection. We will be using Polycom VVX phones.

The speed of the Comcast internet connection is 16 Mbps Download and 3Mbps upload. It is my understanding that we can only control QoS on the upload portion of the connection, so we are working with only the 3Mbps speed right?

Comcast supplies a modem with a Gig-e Copper handoff which we will plug into the GE uplink on the Netvanta 1335. I believe we have to rate limit this port to 3Mbps otherwise the Adtran will think this is a full 1000Mbps pipe right? Does rate limiting the port to 3Mbps also limit the download to then only come in a 3Mbps instead of 16Mbps? I am aware that the Netvanta 1335 is only rated to handle ~35Mbps of traffic.

We will have the ability to have 10 voice calls, so we want to have QoS for up to 10 VoIP calls. A G.711u SIP call uses 87.2 Kbps per call according to Cisco, rounded up to 88Kbps. So we will want to reserve 880Kbps of traffic for voice (88Kbps per call X 10 Calls). So we want to reserve this much incase all users are on the phone. If all users were on the phone 880Kbps would be reserved for voice, and the remaining ~2Mbps upload would we for regular internet traffic. If no one was on the phone than the full 3Mbps upload could be used for internet traffic.

What is the best way to set this up? Any examples or guides?

[Anonymous · Accepted solution]

- Thanks for asking your question on the forum!

You will need to set a traffic-shape rate to your WAN interface on the NetVanta so that when QoS makes its calculations as to its available bandwidth, it uses the traffic-shape rate as opposed to the negotiated speed between the Gig-e handoff and itself.

To set up a QoS map for this, you will need to create a map that matches your voice traffic, and then set the priority to be the 88Kbps you want to reserve for voice calls. The 'priority' keyword will allow that bandwidth to be used by other applications if it is not in use by the voice packets. You can use this guide to read more details regarding QoS: Configuring QoS in AOS You can find examples starting on page 41.

Regarding your question about rate-limiting affecting the download speed, it is possible. I would think you may run into this with TCP transmissions as TCP window scaling comes into play. However, with UDP transmisssions, I would expect the download speed would be as advertised.

Let us know if you have any further questions.

Thanks,

Noor

[Anonymous]

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Thanks,

Levi