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Sending VoIP over the Public Internet

Does any body knos what QoS needed in order to send Voice Traffic over the Public Internet using the Access Server.

3 REPLIES
Cisco Employee

Re: Sending VoIP over the Public Internet

From my perspective it does not really matter what QOS you configure. Whenever you go over the public Internet then you have no control over you data at that point. Doing QOS at the end and not in the middle will not help to much. Anytime you go over the public Internet it is best effort. Hope this helps.

Thank you,

Cisco Employee

Re: Sending VoIP over the Public Internet

Mimckee is correct however there are some things you can do to give you the best chances of getting a quality call.

Queuing strategies and framentation are important to consider given the serialization delay of your internet link. You always want to make sure that you are de-queuing voice packets ahead of data packets, and that you chop up the data packets so your voice packets dont' wait to get dequeued while some 1500 byte data packet is being serialized. Always use ip precedence 5 on your voip dial peer as this may be respected by the unknown routers you hit. I don't know what kind of link you have to the ISP but here is a good link to check out for Qos ideas.

http://www.cisco.com/warp/customer/788/

regards

Sam

Cisco Employee

Re: Sending VoIP over the Public Internet

Queuing strategies will only help on the router where queuing strategies such as LLQ, WFQ, etc. have been configured -- namely, your access router into the Internet Service Provider. Unless you have some special SLA with your ISP, every router hop from there all the way to the other side will almost always be FIFO, so the ip precedence 5 packets will not be honored as such.

Also, fragmentation is really not effective at layer 3 with the IP protocol, since it can so easily break so many applications, like MS networking, HTTP, and others. And fragmentation at layer 2 (such as using frame relay or MLPPP) needs to be configured on both ends of the layer 2 link, which your ISP will not do without again some special SLA.

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