DSL_Ricer
Premium
join:2007-07-22
| reply to andrewhaji
Re: VOIP in the presence of throttling
said by andrewhaji  :I'm a little confused by this thread. Why would BitTorrent throttling affect VoIP? I was under the impression that the throttling only affected BT packets? Under regular circumstances, BT packets only affect VoIP by the fact that they take up time on the line. Classically, if you're uploading faster than your line can take, your router would start buffering and your latency would to the 500-3000ms range and with similarly large jitter. VoIP can't compensate for those kinds of stats. QoS enabled VoIP PAP's and routers came along to solve that. They make sure VoIP packets are put at the front of the buffer, guaranteeing low delays and jitter. The software solution to do the same is to limit uploads to less than what is needed by VoIP.
Bell's throttling is problematic in two ways. First, Bell's throttling doesn't just affect BT. It also affects other protocols.
What Bell most likely classifies traffic into two different categories; let's call them good and bad traffic. Good traffic, like web, is never throttled. Bad traffic like BT isn't always throttled, however, if something triggers the throttling all bad traffic gets capped.
For some reason VoIP is classified in the bad category. Chances are, it's a generic filter that just catches non-whitelisted traffic. However, that still means it gets caught.
As second point, and going back to the QoS routers, a good deal of them function by limiting the total upload to line speed. When bell suddenly throttles, these routers continue on their merry way thinking that nothing has changed. You the start getting large amounts of packet drops and, I'd assume, latency. Bell's throttling renders these devices useless. Other such routers function by limiting to a user supplied value. How many of them would be pleased with entering a number under half of what their line is actually capable of, especially since, for bell, all web traffic doesn't count against this cap, but will for the adapter? The torrent software equivalent for this would be to limit to 10KB/s, or less...
You'll also note the fact that I say I'd assume. All speed tests I know of are web based. Since web traffic isn't throttled, it shows full speed. I have Vonage speed tests (web) showing 4Mbit/498kbit with a quality of service rating of 96% and yet, the same line, under the same conditions, is unable to place a call because not enough VoIP packets are getting to Vonage. During the same periods, switching to a teksavvy login gave me worse overall stats, but the line was 100% clear. |
