VoIP security: knowing your ALGs and H.323s

Whether it's for firewalls or Virtual Private Networks, we're seeing an increasing emphasis on VoIP Security.

The point was hammered home today by a look at the Security Appliances winner in Information Security magazine's 2004 Products of the Year awards.

The triumphant solution is actually two related products: Juniper Networks' NetScreen-5GT and -5XT firewall/VPN appliances. Both products were praised for "expanded VoIP security."

"Expanded" sounded kinda general to me, so I took a look at the specs for each.Both solutions haveH.323 ALG, SIP ALG and NAT for H.323/SIP capabilities.

Odds are that if you care enough about this stuff to spring for it, then you already know what all these terms mean. But for the rest of you, OK, here's a bit of jargon unjangle:

H.323 is a packet-based standard for real-time data, audio and video transmission over IP-based networks, such as the Internet.

ALG is short for Application Layer Gateway, which is a component of of Windows OS. If you use a third-party firewall or Internet Connection Sharing (ICS) to connect to the internet, you'll sure want it around. Do not despair, because you'll probably be able to find it in your c:windowsSystem32 folder.

And unless you are bending elbows at the brewpub, SIP stands for Session Initiation Protocol, an IP telephony signaling protocol used for VoIP calls.