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VoIP over Frame Relay!!!

Unanswered Question
fbahram Mon, 06/24/2002 - 06:30
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VoIP is voice packet with an IP header which in turn has an ip address and can be routed anywhere on the internet. Voice over FR only has layer 2 header, in this case : frame-relay header. There is no ip address so it can only be sent across frame-relay PVCs. VoIP can be sent on any layer 2 protocol (HDLC, FR, ATM, PPP) because it is just an ip packet but a VoFR is not an ip packet, it is a frame-packet like a frame-relay keepalive...has to be run on a frame-relay PVC. Here are some documents below:


(This gets into fragmentation but it explains VoIP vs. VoFR)

Hope this helps.

Hi Ken,

I do not have the list of any documents that you can look at but I guess you can search for Cisco site and the web in general and you will find a lot of info.

Basically, the way it works is this; FR is predominantly a WAN protocol and IP is predominantly used on LANs (although this situation is rapidly changing). Because FR is a layer 2 protocol and conforms to the OSI model, a variety of layer 3 protocols (including IP) can be run over it.

Both FR and IP are packet-based protocols and can be modified to carry voice (VoIP and VoFR). However, in some cases, companies implement voice over IP on Frame Relay circuits provided by the carrier companies, hence the term "VoIP over Frame Relay".

I hope I have been of help. Please let me know if you find anything interesting.


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