Tag Archives: nist

Telco broadband slows at the edge, cable bottlenecks in the core

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Speeds can drop suddenly at the edge.

Slow residential connections keep DSL speeds down, while cable’s problems are further back in the network. Researchers for the U.S. National Institute of Standards and Technology dug deep into data collected in 2011 by the FCC as part of its Measuring Broadband America program.

The NIST researchers asked the question: Where in the Internet is congestion? The results suggested that…

…a significant amount of congestion, especially for cable connections, occurs deeper in the network, perhaps, in the “middle mile”…or even farther, where the ISP connects to the “public Internet”. This is somewhat contrary to the popular belief that the edge is more congested than the core.

The “edge”, or last mile, is defined as the final outdoor segment that connects a home to the first electronic box in a provider’s network, for example a cable node in the neighborhood or a DSL port at a telephone exchange.

One way to read the report is that telcos have better core network infrastructure than cable companies, but where there’s the greatest difference between the two – ageing copper wires versus coaxial cable, DOCSIS versus DSL variants – cable comes out ahead. As the authors warn, though…

It is possible that because our method for detecting tight initial segments underestimates their prevalence, they could still be the dominant cause of recurrent congestion while remaining undetected.

Replacing copper lines over the last mile is an all or nothing proposition; it has to be done all at once in a given area, for subscribers and non-customers alike. Upgrading the core network, though, can be done incrementally as traffic and revenue builds. With the caveat that there’s more research to be done, it appears that telephone companies have a more difficult and costly job to do if they want to deliver faster and better broadband service.

Cable for broadband speed, telcos for consistency in service and advertising

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More likely so.

DSL is better at delivering advertised download speeds than cable, but cable modem service is still faster. That’s one of the conclusions reached by researchers for the U.S. National Institute of Standards and Technology after sifting through broadband test data collected by the FCC in 2011.

DSL broadband provided connections on average delivering download speeds above 80% of the assigned speed tier more than 80% of the time. By contrast, a significant fraction of cable connections received less than 80% of their assigned speed tier more than 20% of the time. One must keep in mind that cable connections typically have higher download speed tiers than DSL connections…the average download speed tier for DSL connections was 5.4 Mbps vs. 13.5 Mbps for cable connections.

In California at least, phone companies tend to be more granular in the broadband availability data they provide to regulators than cable companies. Typically, data for any given city will show a range of advertised DSL speeds across different neighborhoods, while cable companies generally claim to be able to deliver their top tier of service everywhere.

Estimating the actual speeds delivered to customers requires applying a discount to those claims. The NIST data suggests that it is appropriate to apply a steeper discount to cable claims, as I have done in several analyses of the California data. Even so, the resulting estimates still tend to give cable the edge, which is also in line with the NIST findings.

DSL customers are more likely to get the service they think they’re paying for, but with faster speeds, cable customers might not notice the difference.