I use AA VoIP and was too lazy to debug problems getting the Gigasets’ handsets to work and so I just used the ‘call redirect’ feature on AA’s website to redirect incoming calls to my wife’s mobile phone. That worked beautifully, and was enough for what we needed, so that is how it has remained. I don’t think that VoIP was likely to have much chance of working properly with our ADSL lines, possibly because of problems with packet reordering given our bonded multiple lines, although it isn’t certain how much, if at all, that was happening. Also packet loss could have been a problem, either natural packet loss because of overload with competing traffic at times, and possibly because of corruption, unknown because I was not monitoring packet corruption error rates back then and so I wasn’t keeping errors down to zero at all times, as I do now. The slowness of our lines would not have been a problem, but jitter might well have been a big problem and bad bufferbloat in the Firebrick has often been seen, with huge peak latency values reported.
Possibly the Firebricks’ algorithm of prioritising small packets somehow isn’t working, otherwise I wouldn’t expect to see such huge (>500 ms!) latency spikes reported by the PPP LCP ‘ping’ testing carried out in AA’s CQM system’s graphs, seeing as the PPP LCP packets are tiny. It has been a long-time wish list item that Firebricks would support L2 and L3 priority marking, not that that is necessarily going to be enough to help in all situations. I also do wish that AA would fix the bufferbloat problems and do modern active queue management, or even give us a choice of queue management algorithms, plus pony on a stick. I’m not at all sure how much the latency spikes that we see are anything to do with the Firebrick.
Is it possible that my modems could be the culprits instead / as well ? Queues building up that are outside the Firebrick are obviously death, unless priority marking is both implemented and obeyed. I do hope that AA’s VoIP servers L3 priority-mark downstream traffic, as this could help both intermediate routers and my modems to do the right thing, aside from my Firebrick.
