Monday, January 15, 2007

VoIP Qos through Sonicwall Firewalls

I often find myself having to troubleshoot or install VoIP applications for customers. During the course of both installing or troubleshooting the voice quality, I get to see what various networking equipment manufacturers are doing to support this rapidly growing technology and tool for office to office communication and often office to customer communication.

Some networking equipment vendors have embraced the voice of data networks technology and have increased support for their product lines to accommodate it by building in the tools to make the technology work. Others have introduced product lines and offer special support including remote support to help the end-users or VARS deliver the best quality of voice.

One of the vendors which I just had the pleasure of troubleshooting network voip issues on was Sonicwall. The model the customer is using is the TZ170.

They have the enhanced firmware (operating system) installed version 3.2 which supposedly has QoS features and VoIP features in built into the system. They do indeed have some VoIP features, functionality, and configurable items built in but they are mostly designed for SIP and H.323. These are standard protocols that are commonly used in voice over data systems. One of the problems I found with the built-in features was theat mostly were designed to assist in voice data packets getting through the firewall and NAT routing features. But what if the voip solution is designed to work through a VPN? They completely missed that part. These features were useless in the site to site VPN such as the one I was working with.

This customer has multiple tunnels from their main location which has a PBX switch to several of their remote offices that also have PBX switches. They can transfer calls between the phone system and also of course be able to call each other saving money on toll calls. One of the most annoying things I found with these the TZ170 firewalls is while configuring the unit through the web GUI or even just viewing, any page refresh causes the current voice streams to choke. The quality of the sound deteriorates while working on the system itself. I already mentioned that their features for voice over data are useless in a vpn to vpn environement and their bandwidth management is awkward and clumsy.