Comcast's Congestion Catch-22

When Comcast earlier this week received yet another admonition from the FCC about how it was managing traffic on its network, the groanswere heardfar and wide. Here we go again – the draconian Comcast taking a heavy hand with its users.

The FCC’s charge, delivered in a letter to Comcast was this: that Comcast was using the latest version of its congestion management system – the one it had just recently altered in response to an earlier FCC inquiry and demand – to improperly (and perhaps illegally) favor its own voice-over-IP (VoIP) service over competitors.

Even at first glance, the charges seemed slightly off. Wasn’t it common knowledge in the industry that all facilities-based providers did their best to keep their VoIP traffic on their own pipes and away from the public Internet? If Comcast was forced to take a protocol-agnostic route with its management scheme, why would it suddenly be limiting relatively low-bandwidth VoIP packets? At a time when service providers are experimenting heavily with deep packet inspection (DPI)-driven congestion management approaches, could anyone get it right?

Deeper examination leads to more questions: Is the use case that the FCC is questioning really as small as it appears? Did they intend their decision to tweak Comcast on what appears to be a technicality to open up a larger Pandora’s box of questions? And is there any level of network management that a service provider can enable that won’t draw howls of protest – not only from the FCC but from users as well?

Comcast and its main named vendors in the project, Sandvine and Camiant, declined to talk about this issue. But background conversations with multiple sources with intimate knowledge of Comcast’s technical implementation, as well on-the-record interviews with vendors and analysts familiar with the issue, revealed many interesting details, quirks and implications that will ultimately affect not only Comcast but any provider of IP-based networks and services.

Comcast’s Congestion System, Take One

The story of Comcast’s first attempt at congestion management is by now well-known. The MSO got its hand caught in the cookie jar – thanks in large part to sleuthing by the readers of Broadband Reports, as well as a follow-up AP story that blew the issue open for the larger public. Comcast was found to be running a system that used forged TCP packets to throttle back P2P traffic running on its network, including not only BitTorrent but other usage-heavy protocols as well. The system targeted these P2P protocols specifically – not surprising, since traffic carried by such protocols can include very large files such as movies or applications that can eat up massive amounts of bandwidth. The operator may not have been alone in this practice – one report by P2P content provider Vuze claimed the eight largest US-based ISPs all “artificially interrupt” P2P traffic – but Comcast clearly drew the brunt of public scrutiny.

The FCC hit Comcast with letters of complaint and two public hearings, and despite its initial denials and declarations of innocence, it ultimately agreed to change its network management system.