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New Member

VOIP Across Remote VPN Locations

I was wondering if anyone had experience with pumping voice data over VPN connections. Specifically, I'm trying to determine the advantages of keeping our existing frame relay network or switching to a VPN type network. The main issue is whether or not I'll sustain a performance loss by using a VPN WAN solution versus a frame relay setup. The WAN will be confined to the continental US and only on a single Tier-1 backbone provider. SLA's cover <75ms round-trip times with greater than 99% packet delivery. Your thoughts and experience is greatly welcomed!

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New Member

Re: VOIP Across Remote VPN Locations

Cisco recommends that the your return-times be under 150 ms to support VOIP, so if you have SLA's for return-times of <75ms you shouldn't have any problems running voice over WAN. One thing to take into consideration is that you have QoS support on your LAN so that VPN device gets the VOIP traffic before any other traffic. Also make sure that you get the best preformance VPN device possible, the better the VPN processing preformance the greater the voice quality you'll get. The VPN will add a bit of degrade to the Voice quality just because the traffic is encapsulated, passed through a router over backbone then back over a router and decapsulated before getting to the otherside. Also make sure that if the VPN device is running a firewall that it supports VOIP pass through, many firewall's no mattter how you configure them will cause problems with VOIP traffic.

New Member

Re: VOIP Across Remote VPN Locations

Don't forget the effect of large packets. Will the WAN support packet fragmentation and interleaving?

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