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Connecting existing PBX's via cisco equipped frame-relay network

Consider a scenario where you have a frame-relay network with 4 sites using 2600/3600's. I want to connect the 4 existing PBX's (different manufacturers)together with 4 digit dialing. The way I see it I have 2 options, I can put NM-HDV's in the 2600/3600's and use dial peers and use a T1 to connect each PBX to the 2600. Then from there the NM-HDV/2600 will convert the traffic to VoIP and connect to the remote site PBX. I think this would be the traditional Cisco voice solution for toll-bypass right?

The second option would be to put IP trunking cards in each PBX (they are different PBX brands so we would have to do qsig?) and set up QoS.

Where it gets cloudy for me is what are the advantages of having the router doing the VoIP stuff on the NMHDV with dial peers and sending it across the WAN rather than having the PBX doing the VoIP and letting the 2600/3600's only see data with QoS priority.

Any light you could shed would be helpful

thanks

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Re: Connecting existing PBX's via cisco equipped frame-relay net

Different PBXes have differing ways that they implement "IP trunking", and not all compy with any sort of standard. Getting them to interoperate is an iffy proposition at best, but I don't know what brand of PBXes you have.

Using Cisco voice hardware to connect to the PBXes guarantees interoperability. You have the option of using any trunk type, even falling back to analog FXS or E&M interfaces if you can't get or don't have room on your PBX shelf for channelized T1 or PRI interfaces. Trunk types don't need to match from site to site. If you use PRI interfaces and configure your PBXes appropriately, you can get station-level caller-ID end-to-end.

If you use IP trunking between differing PBX brands, it is unlikely that you could implement reliable call admission control (limiting number of calls that could enter the IP network so as to not exceed available bandwidth). Using a Cisco voice hardware based solution, this is easy and reliable.

As a shameless plug, using Cisco voice hardware would permit easy and gradual migration to a pure IP telephony solution using Cisco CallManager.

2 REPLIES
Gold

Re: Connecting existing PBX's via cisco equipped frame-relay net

Different PBXes have differing ways that they implement "IP trunking", and not all compy with any sort of standard. Getting them to interoperate is an iffy proposition at best, but I don't know what brand of PBXes you have.

Using Cisco voice hardware to connect to the PBXes guarantees interoperability. You have the option of using any trunk type, even falling back to analog FXS or E&M interfaces if you can't get or don't have room on your PBX shelf for channelized T1 or PRI interfaces. Trunk types don't need to match from site to site. If you use PRI interfaces and configure your PBXes appropriately, you can get station-level caller-ID end-to-end.

If you use IP trunking between differing PBX brands, it is unlikely that you could implement reliable call admission control (limiting number of calls that could enter the IP network so as to not exceed available bandwidth). Using a Cisco voice hardware based solution, this is easy and reliable.

As a shameless plug, using Cisco voice hardware would permit easy and gradual migration to a pure IP telephony solution using Cisco CallManager.

New Member

Re: Connecting existing PBX's via cisco equipped frame-relay net

Jason, thanks for the great response. A lot of good info here to put me on the right track. The PBXs are all nortel and avaya. I am going to push for the Cisco voice solution even though nortel will probably come up with some "IP enabled" pbx solution. One advantage I have is that they are very interested in cisco's IP Key switch (I think they renamed it to IOS telephony services or something) where you can sort of run call manager on a router for small 10 or 15 phone locations.

Thanks again for your help Jason

ryan

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