Slow ADSL Download Speeds

Got an ADSL connection that’s running slow?  Downloads taking too long?  Wonder if there’s anything you can do to speed things up?  Maybe, maybe not.

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Note:  The bulk of this post was originally in response to a question from someone who was getting only 1Mbps download speeds on their ADSL connection.  Since the issues are the same regardless of how slow your connection is, I figured I’d post it here and expand on it if folks are interested.  Whilst some of the content is specific to Australia, most of it is generic and applies to ADSL connections anywhere.

Real world ADSL speeds are primarily limited by the distance to the exchange and then by line noise.

Before you do anything else, make sure that you actually have a problem by checking units.  Mbps is not the same as MBps.  1MBps is fine, but 1Mbps is very low for ADSL.  There are 8 (b)its in a (B)yte, so 1MBps is actually 8Mbps.  Lots of applications report transfer speeds in MBps and they aren’t always consistent (or correct) in their capitalisation.  Use something like speedtest.net to verify your download speed in Mbps.

Assuming that you do indeed have a download rate of 1Mbps, then the next thing you need to check are the laws of physics.  Signals lose strength as they travel down copper wires, and since download speeds are linked to signal strength that means the further away from the telephone exchange you are, the slower your download rate will be.  Use something like adsl2exchanges.com.au to find out what your estimated maximum speed should be.  If you’re within 40% of this number then you don’t have a significant problem (cable runs are often much longer than straight-line distances).

If you can’t get an estimated maximum speed from the above website, or another similar website, but you can get a distance to the exchange, then use the distance with the following chart (from Internode) to estimate your maximum speed yourself:

internode-adsl2-dist07

If what you get from speedtest.net is less than 60% of the maximum rate that you could get according to adsl2exchanges.com.au then there’s likely to be a problem somewhere.  How significant a problem depends on how big the difference is.

Line noise is the next biggest limiting factor.  Bean-counters at Telecom/Telstra have forced technicians to use cheaper, sub-optimal compounds to moisture-proof connections for over two decades with the consequence being that, when it rains heavily, junction boxes and pits flood, water often penetrates the connections, and low-level short-circuiting occurs.  You can tell if this affects you because when you go to make a phone call (using your analogue land line) just after a decent rain, you’ll hear lots of static, crackling and pops on the line — line noise.

Since your ADSL rides on top of the underlying carrier signal, whenever that signal gets disrupted, you lose packets and your Internet application needs to re-send those packets.  This is known as ‘packet loss’.  Having to re-send lost packets takes time and slows down your transfer speeds.  If you have a decent router, you could log into the router’s web interface and bring up a chart or some statistics showing you how much packet loss your line is experiencing.  If packet loss increases after local rains, but is negligible during dry periods, then that’s your problem.

The real problem, however, is getting it fixed.  If you detect line noise and report it to your ISP then they’ll open a ticket with Telstra who will take, at least, two days to get back to you.  By that time the rains have stopped, the junction boxes have emptied, the connections have dried out, and the signal noise is gone.  So when the technician rocks up and test your line, the device they use reports that the line is working fine.  /sigh

The final source of line noise is within your house.  This is a vast topic in and of itself, but basically the more phone sockets, connections, splitters, adapters, extension lines, analogue phones, security systems, and so-on that you have connected to your line, the more line noise there will be.  As an experiment, you could disconnect absolutely everything from your phone system, then connect only your router to the master/main phone socket (the one closest to where the line comes in from outside) and do a speed test with that.  If there’s a big improvement in speed then one of the things you disconnected must have been causing substantial amounts of noise.  Shouldn’t be too hard to work out which one if that’s the case.

Optimising an Internet connection is not a trivial process.  You need to be prepared to research all of the relevant issues and absorb and understand technical information.  There is no magic green ‘go fast‘ button that you can press.  Sometimes 1Mbps is as good as it gets!  The location of your house, the location of the exchange, the condition of the line between them, the laws of physics — none of these care about whether or not you are happy with the speed of your Internet connection, and you usually can’t change (‘fix’) any of them.

The best you can do is simplify the wiring within your home, and maybe try a different router (to address chipset incompatibilities).  If that doesn’t fix the problem, then the problem probably can’t be fixed.  You then have no option but to use a different technology to connect to the Internet (cable, fixed wireless, HFC, mobile, fibre…).

Finally, this problem isn’t going to get better in Australia — it’s only going to get worse.  The government is basically abandoning the copper network (and everything that relies on it).  This is clearly evident in how the NBN operates.  If you get a new NBN connection, they will decommission your land line within 18 months — literally cut it off.  The writing is on the wall for the copper network.  That’s why no-one is really interested in fixing house-to-exchange line noise issues — crumbling infrastructure and slow speeds are a good way to ‘encourage’ users to stop using the copper network and switch to the NBN.  You can voluntarily walk the plank, or wait until you are pushed — either way you are leaving the ship.

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