In line with their traffic management website
Comcast has confirmed to us they've installed their new broadband throttling system across all markets. The system, which we first profiled back in September
, throttles a user's connection if
a particular CMTS port is congested, and
if that user has been identified as a primary reason why. This two-condition throttling system replaces Comcast's old, FCC-criticized system of using forged TCP packets to throttle upstream P2P services for all users, regardless of consumption.
According to Comcast's filings
(pdf) with the FCC, they've deployed new hardware and software close to the company's Regional Network Routers (RNRs). This hardware will flip a user from the standard "Priority Best-Effort" traffic (PBE) to lower quality of service (QoS) "Best-Effort" traffic (BE) for fifteen minutes if they're a major reason congestion exists.
While certainly a slightly more transparent system to those paying attention, the new system is probably going to confuse the American public, many of whom don't even know what a gigabyte is
. Comcast used a bus metaphor to explain the difference between best effort and priority best effort traffic to the FCC:
If there is no congestion, packets from a user in a BE state should have little trouble getting on the bus when they arrive at the bus stop. If, on the other hand, there is congestion in a particular instance, the bus may become filled by packets in a PBE state before any BE packets can get on. In that situation, the BE packets would have to wait for the next bus that is not filled by PBE packets.
Comcast says that sustained use of 70% of your up or downstream throughput triggers the BE state, at which point you'll find your traffic priority lowered until your usage drops to 50% of your provisioned upstream or downstream bandwidth for "a period of approximately 15 minutes." A throttled Comcast user being placed in a BE state "may or may not result in the user's traffic being delayed or, in extreme cases, dropped before PBE traffic is dropped."
Note that upstream and downstream bandwidth are managed separately. Also note that the differentiation between PBE and BE traffic occurs in two millisecond increments. According to Comcast, even if the packets for a best effort throttled user missed 50 "busses," the delay would only be about one-tenth of a second.
In addition to the new throttling system, Comcast has also a 250GB monthly usage cap for all users. As we mentioned last Friday
, Comcast has confirmed that a web portal-based bandwidth tracker is currently in beta among Comcast employees -- but has yet to give an official launch date. A Comcast insider had previously given us leaked screenshots
of the monitor, and said it was originally scheduled to go live on January 5 (today).
Comcast has confirmed to us that they've completed the upgrade to the new system.