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VOIP Pros and Cons

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by pyman51

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We have a sales office 100 miles from our HO currently connected for data and phone by an expensive Leased Line (kilostream link). As we already have a Citrix and NFuse environment in place for our remote home users, I plan to save the high cost of the kilostream link by bringing the two users in our sales office in line with our home users by using a broadband connection instead. This would work very well for their computer data requirements but they need to retain their phones as extensions of our HO system. I understand that SIP phones may be the answer, but do they work with ISA servers and DMZs? What compatibility, reliability and security issues do I have to consider? What are the Pros and Cons?

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by georgeou

ISA servers won't let you traverse SIP but that isn't a problem if you're only trying to use some SIP phones through an internal network through a VPN.

SIP phones use about 40 to 80 kbps and maybe another 40 kbps on top of that if you're going through a VPN tunnel because of additional overhead. If your ping to your VoIP PBX is less than 100 ms and you have enough bandwidth to accommodate 120 kbps in both directions, then VoIP will work.

But for small remote offices, consider using a Lingo or Vonage account that offers unlimited calling to North America for a fixed 25 to 35 dollars a month. $10/month more for all Europe plan too. That way you don't even take up resources on your VPN tunnel at your head quarters.

by pyman51

Thanks very much for your very useful reply. We are based in the UK (St Ives in Cambridgeshire) but I expect the technical part of your comments is still valid. Do you, or anyone else out there, have any experience of doing what I hope to do?

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