Jared Valentine has posted an interesting description of a system he developed for automatically manipulating QoS & bandwidth allocation to support the use of VOIP over his DSL service. He calls this “Application Aware Triggered QoS.”
He described his initial problem as being trouble with inbound bandwidth management. This is something that I’ve never experienced myself. My trouble was always related to limited outbound bandwidth.
His process for understanding what was going on is an excellent example of how to analyze network traffic. His solution, while interesting, is probably not appropriate for everyone.
He uses a combination of Snort and pfSense to monitor network traffic, sensing the presence of SIP call setup signaling. When a call is sensed he fires a command to his Cisco router to engage rate limiting such that the call can proceed ideally. Once the call has been completed he automatically disables the rate limiting.
I did say it was novel, right? It’s like intrusion detection for VOIP.
He says very plainly that all he was seeking was one Vonage line, and that he had to severely throttle his allowable download speed to get clear calling. While Jared’s DSL service is said to be 1.5 Mb x 1.0 Mb he says that he had to limit to 800k download for the Vonage line to work correctly.
I wonder what Vonage interface device he was given? They have some with built-in routers and QoS is supposedly assured. I also wonder if he tried using Vonage’s low bandwidth setting? It just chooses a low bandwidth codec…very likely G.729a or a G.723 variant.