How Comcast Will Curb Hogs

9/26/2008 8:00 PM Eastern

Comcast will use equipment from Sandvine, Camiant and a third yet-to-be-determined vendor to temporarily throttle back the speeds of the heaviest Internet users during times of network congestion.

The cable operator outlined the plans to migrate to a “protocol-agnostic” bandwidth-management technique by the end of 2008 in documents filed with the Federal Communications Commission Sept. 19. The company was responding to an FCC order that it stop specifically targeting peer-to-peer applications, and adopt a more neutral technique.

Getting Agnostic
Comcast’s new bandwidth-management technique will:
SOURCE: Comcast FCC filings
Limit access speeds based on overall usage rather than specific protocols or applications.
Temporarily deprioritize traffic for subscribers who use an average of 70% or more of provisioned upstream or downstream bandwidth over a 15-minute period during network congestion.
Restore full service to those excessive users once usage falls below 50% of provisioned bandwidth for 15 minutes.

“The goal of Comcast’s new congestion management practices will be to enable all users of our network resources to access a 'fair share’ of that bandwidth, in the interest of ensuring a high-quality online experience for all of Comcast’s [high-speed Internet] customers,” the company said in the filings.

Sandvine, in a statement last week, said terms of the agreement have not yet been finalized. Based in Waterloo, Canada, Sandvine demonstrated the Fairshare system at The Cable Show ’08 in May.

Comcast acknowledged that it currently uses Sandvine’s Policy Traffic Switch 8210 to limit the number of upstream connections for five P2P applications that consume an extraordinary amount of bandwidth: BitTorrent, Ares, eDonkey, FastTrack and Gnutella.

Under the new technique, Comcast will use the vendor’s Fairshare tool to determine when a cable-modem termination system port is close to being congested.

In addition, the MSO said it will use Camiant’s PacketCable Multimedia servers to instruct a CMTS which specific modem should be curtailed.

A third component, an Internet-protocol detail record server, will analyze cable-modem volume usage. Comcast said it has not yet selected that vendor.

Comcast expects to cut over to commercial deployment of the protocol-agnostic systems starting Nov. 15, with its entire footprint converted by Dec. 31, according to its FCC filings.

In March, Comcast had said it would move to a protocol-agnostic approach by year-end.

The system will deprioritize bandwidth for “high-consumption” subscribers, which Comcast defined as ones who have used an average of 70% or more of his or her provisioned upstream or downstream bandwidth over a particular 15-minute period during times of network congestion. A user is removed from the penalty box once his or her usage falls below 50% of provisioned bandwidth for 15 minutes.

Comcast currently operates about 3,300 CMTSs, serving 14.4 million high-speed Internet customers. On average, the company said in the FCC filings, about 275 cable modems share the same downstream port and about 100 share the same upstream port.

Based on its trials of protocol-agnostic management platforms, Comcast said, fewer than one-third of 1% of subscribers have had their traffic priority status flagged for excessive consumption. For example, in its test in Colorado Springs, Colo., last month, an average of 22 users out of 6,016 total in the trial market were affected at some point during the day.

Comcast told the FCC it has yet to receive “a single customer complaint in any of the trial markets that can be traced to the new congestion management practices, despite having broadly publicized its trials.”

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