Throughput of an ADSL2+ Connection

In our apartment we have a Adam Internet Naked ADSL2+ connection. Our Billion BiPAC 7401VGPR3 modem reports a sync speed of 21.302Mbit/s downstream and 1.176Mbit/s upstream. The high sync speed is probably attributed to the 150m as the crow flies between us and the exchange. Adam’s control panel reports a 5.1dB SNR, the modem roughly agrees at 5.5dB. We are using the Adventurous line profile that provides 24Mbit/s with interleaving. There is one higher speed line profile that turns off interleaving, but this increases the likelihood of transmission errors.

Enough of the details, this post is about collecting some real-world throughput data. The idea comes from Vincent’s blog, which I read through Planet Debian. He is trialing a high speed internet service, and used curl to perform some throughput testing. In his case the servers tested were not up to his 50Mbit/s connection; something to think about with our 1000Mbit/s National Broadband Network on the way.

Using Vincent’s method of scraping curl‘s output, which provides a throughput every second, and displaying using gnuplot, I collected a number of data sets. I tested using the file servers of Adam Internet;, as well as those of Internode, another local ISP that peer with Adam Internet.

The bash and gnuplot scripts used to produce the data, as well as the source data, is here. If you’re interested in running the tests yourself, use a large file from your ISP. Whilst my ISPs have test files, I instead chose an Ubuntu ISO as the file size is consistent across mirrors. Credit goes to Vincent for both snippets.

Late night and Early Morning

The first graph shows the difference between night time and weekday morning throughput. Adam have an off-peak period that allows dowloading from midnight until 8am, meaning many users queue up large downloads to complete over night. On the other hand, during business hours there are more people awake and using the net, so it is hard to draw any conclusions without looking at the ISP’s data.

Friday Evening

I also took a look at the difference between downloading the file from my 100BASE-TX switched wired network, versus the 802.11g WiFi network. A laptop to server file transfer is greater than the 2Mbit/s observed on the DSL connection, so the throughput characteristics of the WiFi should not matter. I was interested to see if the extra 0.5ms of latency that the WiFi network brings would make a difference. The answer is yes, by a small margin.

Friday Evening: WiFi and Wired

The most interesting result of these tests was Internode’s mirror gave higher throughput than the mirror provided by my own ISP. This comes with some surprise, and I do not have any suggestions for why it is the case. If you have a theory as to the discrepancy in throughput please leave a comment.

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