Bandwidth Crunch Will Yield Changes


The following was written and submitted by the staff of Cable Television Laboratories Inc. to coincide with this week's Society of Cable and Telecommunications Engineers Cable-Tec Expo in Philadelphia:

Bandwidth usage among cable's broadband Internet customers is rising steadily, driven in part by an increasingly media-rich World Wide Web, and by customers who continue to weave the service into their everyday lives.

That's according to an ongoing study of bandwidth trends by Cable Television Laboratories Inc. CableLabs has analyzed the cable modem traffic of over a half-million anonymous customers, served by more than a dozen North American cable operators. Now in its third year, the bandwidth management team has analyzed more than a million Gigabytes worth of raw data.

"We estimate that the average customer traffic has been growing at the rate of about three percent per month," says David Reed, chief technical officer at CableLabs. In addition, most broadband Internet customers consume less than a Gigabyte of data per month.

But the "heavy users," which represent about 4% of overall cable modem subscribers, generate or receive roughly half of all overall monthly traffic, says Reed.

In the upstream signal direction, peer-to-peer (P2P) traffic is the big usage driver, says Terry Shaw, director of network systems for CableLabs. P2P activities occur when broadband Internet customers knowingly or unknowingly apportion their personal computer to share large audio and video files with one another.

Shaw culls the raw cable-modem data monthly, and examines it from three perspectives: Volume, throughput rate (volume plus time), and symmetry (the ratio of downstream traffic to upstream traffic.)

Gathering the data involves counting the data in bytes on the cable-modem side of the cable-modem termination system, as it travels upstream and downstream. Individual and aggregate levels are counted, in order to have more analytical context. Packets are only counted, not examined, for obvious privacy reasons.

To date, the numbers portray fairly predictable usage patterns. On weekdays, traffic begins to build in the mid-afternoon, and peaks at around midnight. On weekends, traffic starts increasing earlier in the day.

Specific traffic patterns reflect local dynamics, which can and do vary by region, and even by neighborhood. What happens in San Diego may not happen in Toronto, especially in February: The farther north one travels, the higher the overall Internet usage during winter.

In general, traffic also spikes noticeably during school vacations, holidays, and during the period in May when students are preparing for final exams. Usage goes up and stays up during the summer.

Cable operators who are planning or engaging in upgrades to Data Over Cable Service Interface Specification 1.1-based cable modems will be able more effectively to track bandwidth consumption and throughput, although techniques for both actions do exist in the DOCSIS 1.0 version of the specification.

And tools for monitoring bandwidth are increasing along with overall bandwidth usage, added Shaw.

For now, according to Reed and Shaw, cable's hybrid-fiber coax networks have the capacity they need to stay ahead of bandwidth usage. In most cases, operators are considering implementing service tiers to rationalize the usage of heavy users that will free up more capacity for the average users.