Canada's Radio-television and Telecommunications Commission (CRTC) famously decided last year to allow Bell Canada to single out P2P traffic for bandwidth throttling between the hours of 4:30pm to 2am. But even as it allowed a practice that the US Federal Communications Commission had just put the kibosh on, the CRTC also launched a much broader hearing on the entire issue of network neutrality.

With the ISP responses now in, it's clear just how widespread deep packet inspection (DPI) has become at Canadian ISPs. It's enough to make staff Canuck Frank Caron weep into his Molson's.

Cold-filtered Internet

Christopher Parsons, a grad student at the University of Victoria (the Fightin' Vikes!), has done yeoman's work by combing through the numerous (and lengthy) ISP submissions to CRTC and compiling them into a set of tables (PDF). This makes it simple to compare responses across ISPs, and one of the obvious places to start is with filtering. So who uses DPI to throttle Internet traffic?

Bell Canada: Yes, with a vengeance, but only P2P between 4:30pm and 2am

Cogeco Cable: Yes

MTS Allstream: No

Rogers Cable: Confidential (but probably yes)

Saskatchewan Telecom: No

Primus Telecom: No

Shaw: Yes

Barrett Xplore: Yes, and also prioritizes VoIP

TELUS: No

Bragg: Confidential

The list above might make it seem that only half of Canada's responding ISPs use filtering, but a bare list takes no account of size. Bell, Rogers, and Shaw are three enormous ISPs that together dwarf everyone else on the list, and all three appear to be throttling traffic.

What kind of traffic? Peer-to-peer, of course. Cogeco says that heavy P2P use as far back as 2001 led it to adopt throttling schemes. Bell notes that its DPI gear was at first just intended for billing, but the company then decided that it needed to use it for throttling as well. Rogers wanted to avoid becoming "the world's buffet," whatever that means, and so clamped down on P2P because of its "unfair" use of many concurrent TCP connections.



Throttling in action at Bell Canada

The cable providers are generally concerned about their upstream bandwidth (as was Comcast in the US), since it is far lower than downstream and is shared with an entire neighborhood of homes. A few P2P users are capable of gumming up the upstream link for the entire node.

Many ISPs, even those not currently throttling traffic, still want to move to a usage-based pricing model. Most companies, including Bell, are shifting to a usage-based pricing model, though several are willing to combine consumption caps with throttling. (Bragg, which has already tried usage caps in the past, notes that customers responded poorly to them.)

When it comes to disclosing the existence of throttling, it's clear that most ISPs would really prefer not to make a public production. When Shaw introduced Arbor-Ellacoya DPI gear into its network, for instance, it didn't notify customers. Rogers, likewise, does not "proactively" notify customers about its management practices. Cogeco won't provide detailed information about what it does because that might allow the bad guys to bypass its systems. Others put the information into legal documents. Bell Canada goes so far as to offer a FAQ and a way to report problems with the throttling system, though this may be due more to Bell's recent CRTC hearing than to the company's love of transparency.

And speaking of transparency, most of the important information in the filings was provided on a "confidential" basis and is not currently available to anyone but CRTC staff. This includes link utilization thresholds, detailed traffic growth numbers, and (most) vendors of the DPI gear involved in the throttling.

CRTC is moving rapidly with the proceeding, and all final reply comments are due by the end of April. A public hearing is set for July 6 in Gatineau, Quebec, after which the CRTC will presumably rule on the question of just what sorts of bandwidth throttling measures Canadian ISPs will be allowed to take.