BT is throttling all of its broadband customers' bandwidth at peak times, not just heavy users, according to independent monitoring data.
Early findings from a new hardware-based monitoring project by ISP analysis outfit Samknows show that even customers who use their connection lightly have non-port 80 traffic slowed to about 15 per cent of the normal speed in the evening, when load on BT's network is high.
Port 80 is used for HTTP web traffic. Samknows used tests on other ports to simulate peer-to-peer traffic, so even a casual BT downloader who grabs a TV show from BitTorrent faces the throttle.
Samknows boss Sam Crawford told El Reg: "Everyone knew that BT does traffic shaping. What's surprising is that they seem to do it to everyone."
A BT spokesman confirmed Samknows' data. He said its throttling does apply to all customers, but emphasised it is only for peer-to-peer applications and does not affect streaming services such as BBC iPlayer.
BT's non-port 80 result also sets the UK's largest ISP at odds with its competitors, who target the minority of so-called bandwidth hogs to maintain speeds for the rest of their subscribers. Virgin Media, the number two provider, slows down line speed for all applications at peak times for the heaviest 5 per cent of users. Others identify users hammering BitTorrent or Usenet and use intelligent monitoring gear to restrict only those protocols.
The BT spokesman said it does the latter, so why its bandwidth profile is so different is somewhat mysterious. The 10 other major ISPs tested scored similar results for non-port 80 traffic and port 80 traffic. Plusnet, which is part of the BT Group and uses the same Ellacoya traffic management hardware as BT Retail, showed a the same pattern as its big brother, albeit with non-port 80 traffic restricted to about 35 per cent of normal speed.
Like all ISPs, BT's broadband packages are subject to a fair use policy, which states both that heavy users will be throttled and that peer-to-peer is sometimes restricted. According to Samknows, it's restricted every day.
Of course, restricting non-port 80 traffic for all customers boosts HTTP speeds for BT customers. It came top of the pile for web browsing, with port 80 traffic coming down at an average of about 85 per cent of potential maximum line speed.
You can find the full Samknows report here (pdf). It's now planned that the ongoing project will be expanded to a much larger sample of broadband subscribers. ®