Feeds

Researchers seek Internet's choke points

DSL more resilient than cable when the chips are down

The essential guide to IT transformation

Cable Internet access really is faster than DSL – but paradoxically, cable users get less of the throughput they think they're paying for.

That's one of the conclusions of a study* from America's National Institute of Standards and Technology (NIST) which ran the slide-rule over datasets captured under the FCC's Measuring Broadband America project.

While American DSL users only get an average download speed of 5.4 Mbps compared to cable users' average speed of 13.5 Mbps, there's a problem: the highest speed available to DSL is far below that available on cable.

The study, by Daniel Genin and Jolene Splett, also took into account what speed tier a customer is signed on for – as the authors state:

“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.”

To try and explain that disparity, the authors took the Measuring Broadband America data to try and identify choke-points in the different networks. The data is collected by SamKnows, which uses test units installed in more than 10,000 customer premises across 16 ISPs.

Their conclusion is that something about ISPs' network architecture makes cable networks more susceptible to recurrent congestion than DSL networks: “The difference in consistency of service is reflected in the number of connections with recurrent congestion, a relatively low 9–12% for DSL in comparison to 27–32% for cable connections”, the report states, adding that several cable providers in the test “have disproportionately high concentrations of recurrently congested connections”.

For this, a definition of a term used in the report is necessary. In working to identify congestion, Genin and Splett work with a concept they describe as a “tight initial segment”: “all network devices between consecutive IP router interfaces, i.e. all network devices and links between the users side of the connection and the terminal node(s) of the initial segment.”

Interestingly, they also found that DSL appears more resilient in the presence of a “tight initial segment”.

“In the case of DSL 37–50% of the connections identified as having a tight initial segment also experienced recurrent congestion, whereas for cable connections the same number was 91–100%," the study says, going on to explain "That is, a tight initial segment virtually always coincides with recurrent congestion for cable connections but more than half of DSL connections manage to deliver performance close to speed tier in spite of a tight initial segment.”

It's a pity that Genin wasn't able to uncover enough fibre connections on the Measuring Broadband America project to add fibre into the mix. However, The Register notes that Verizon's fibre product was measured in February to be delivering 120 percent of advertised speed, averaged across all speed tiers.

The study is available on Arxiv, here. ®

Bootnote: Since this story was published, the lead author of the study, Daniel Genin, has asked The Register to make it clear that the study was published in a personal capacity only, and not as part of any NIST project.

"The paper was authorized for a submission to the Infocom 2012 but since it was rejected from the conference it was never published. I decided to submit the paper to arXiv to receive additional feedback from the research community and never expected that it would be figuring so prominently", Genin told The Register in an e-mail. ®

Boost IT visibility and business value

More from The Register

next story
Pay to play: The hidden cost of software defined everything
Enter credit card details if you want that system you bought to actually be useful
HP busts out new ProLiant Gen9 servers
Think those are cool? Wait till you get a load of our racks
Shoot-em-up: Sony Online Entertainment hit by 'large scale DDoS attack'
Games disrupted as firm struggles to control network
Silicon Valley jolted by magnitude 6.1 quake – its biggest in 25 years
Did the earth move for you at VMworld – oh, OK. It just did. A lot
VMware's high-wire balancing act: EVO might drag us ALL down
Get it right, EMC, or there'll be STORAGE CIVIL WAR. Mark my words
Forrester says it's time to give up on physical storage arrays
The physical/virtual storage tipping point may just have arrived
prev story

Whitepapers

Top 10 endpoint backup mistakes
Avoid the ten endpoint backup mistakes to ensure that your critical corporate data is protected and end user productivity is improved.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Backing up distributed data
Eliminating the redundant use of bandwidth and storage capacity and application consolidation in the modern data center.
The essential guide to IT transformation
ServiceNow discusses three IT transformations that can help CIOs automate IT services to transform IT and the enterprise
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.