During some recent testing of traffic shaping I found that ingress traffic policing was important to maintaining low latency for high priority traffic such as VOIP. Unfortunately the traffic policy abilities of the Linux kernel are crude and limited to simply dropping packets over a given rate for specified conditions. This keeps latency low but requires the dropped packets to be retransmitted thus wasting bandwidth. IMQ has been one way of addressing it. Anyway I noticed that new IMQ patches were available for more recent Linux kernels and iptables versions. However, at the moment I’m more interested in trying the successor to IMQ, IFB (Intermediate Functional Block), which is supported in Ubuntu 7.10 (Gutsy Gibbon).