Technology overview

Question: Can you briefly explain how VPN technology works?

Answer:  What we mean today by VPN is that it's essentially an encrypted tunnel carrying communications over an unsafe network.  There are basically two types of VPNs. The first type we call remote access.  It typically involves employees working on their PCs from home or a hotel room and connecting to the office network. So it's their PCs to a server. You have VPN software or hardware on each PC, at the office, and you have a VPN server.  Another type is the wide area network (WAN) replacement VPN. In the old days, nationwide companies could connect their East Coast and West Coast office networks using leased lines or frame relay or whatever. Today, we can do that over the Internet with a WAN replacement VPN or a site-to-site VPN.

Question: How do they differ in terms of technology?

Answer: The major difference is that a WAN replacement VPN is server-to-server, so there's no PC involved. The second thing is that generally, on the WAN replacement side, you might have 10 or 15 nodes. Everybody's connected to everybody else in a mesh type network.  With remote access VPN, you might have hundreds or thousands of nodes.  It's very much many-to-one.  It's all of them back to one server, maybe two servers, so it's a many-to-one kind of connectivity, and it's server-to-PC versus server-to-server.

 

Reliability and performance

Question: How reliable are VPN connections?

Answer: That's the major downside of VPNs.  They use the Internet instead of dedicated telephone lines, so reliability and performance are no better than the reliability and performance of the Internet. And they're no better than the reliability and performance of the ISP you're using and the ISP your company's using.

So if you're on the VPN and all of a sudden everybody starts downloading the Monica Lewinsky transcripts or there's a new video of Madonna's wedding and everybody's downloading that, and the Internet starts taking performance hits, your VPN performance is affected.

VPN Viability

Question: Are there circumstances when VPN technology is the best solution and circumstances when it is not a good idea?

Answer: Where it's not a good idea is with performance- or latency-sensitive applications. For example, when you're checking your e-mail, if it takes one second to download one message one time and 10 seconds the next one, it might be annoying, but that's still okay; you're still going to be able to read your e-mail. But anything that's either trying to operate in real time or is sensitive to throughput and latency is not a good candidate to run over VPN.

 © 2001 TechRepublic, Inc.