Tech Questions: When the internet isn’t performing well (or at all), what’s the problem?

Internet performance issues can be difficult to diagnose, but are generally traceable to four issues:

  1. ISP-related problems
  2. Bandwidth limitations
  3. Network limitations
  4. Website problems

Internet Diagram

In order to access the internet, data sent from or to your computer must travel through a series of devices and connections.  First, the computer connects to the wireless access point (if wireless), and then to a network switch, of which there are about 20 throughout the district.  From the network switch, the data is sent through as many as two additional switches to get to the district’s internet firewall, from which the signal is transmitted to Heartland AEA in Johnston, which hosts another firewall, and then to our internet service provider (Iowa Communications Network) in Des Moines.  From there, data is sent to its internet destination.  The response from the web server that you are connecting to then travels back through the same chain to get back to you; all of this happens in a tiny fraction of a second, with each piece of equipment along the way adding just a tiny bit of latency when things are working well.

Every now and then, though, problems arise with our network connections.  Problems that we experienced early in the year were almost entirely caused by issue #1 above, ISP-related problems.  As illustrated, all of our traffic must travel through an internet service provider to reach the broader internet, just as it would from any internet-connected home or business anywhere in the world.  For the first month or two of this school year, our ISP (the ICN) ran into issues whereby it was providing school districts, aggregated through Heartland AEA, with over 2Gb of bandwidth, but due to a routing issue all traffic was being funneled through a 1Gb connection between the AEA and the ICN.  This resulted in us receiving far less bandwidth than we should have access to (40Mb), and at times our bandwidth allocation dropped to almost nothing due to this problem.  This issue aside, the ICN has generally been a very reliable ISP, with a 99% uptime record for years.  That said, issues that can impact the ISP (and thus, us) at any time range from routing and equipment issues like that described above, to problems resulting from power outages and cut fiber optic cables (call before you dig!), to name a couple.

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The most common cause of internet performance issues, however, is that of bandwidth limitations.  Two years ago, the ADM Schools had access to about 7Mb of bandwidth, with that number increasing to 25Mb partway through the 2011-2012 school year.  Prior to this school year, the district purchased 40Mb of internet bandwidth, with plans to increase this amount again for 2013-2014.  The graph above shows our bandwidth utilization for a fairly typical six-hour period.  As you can see, we hit our 40Mb maximum transfer rate several times during the day, but only once for a somewhat prolonged period of time (approx. 11:30 to 12:00).

Bottleneck

While we are not generally maxed out, a computer lab full of students streaming videos, a cart full of iPads downloading new applications, or a server downloading a large file update are all examples of instances where our bandwidth can quickly spike to the maximum level.  When this happens, a bottleneck is created whereby traffic gets backed up behind the connection to the internet, and must wait its turn to get through (in effect).  Think of this in terms of a roadway where a lane is closed; if more cars are arriving per minute at the construction zone than can physically pass through it, a backup will occur.  Each winter the tech department analyzes usage data and looks at equipment and service projections for the upcoming year to determine whether to increase our available bandwidth.  While bandwidth is not inexpensive, the costs associated with a mid-year increase – which would not be subsidized in the way an annual increase would be – are staggering.  As such, we try to guarantee that we’ll go into each year with a bandwidth amount that will be adequate but not wasteful.

Far less common than internet bandwidth issues are internet performance problems arising from network limitations.  These are generally caused by bandwidth bottlenecks as well, but rather than being caused by the internet bandwidth not being sufficient, they’re caused by problems in other areas of the network.  To illustrate the problem, let’s say that a computer lab with 30 computers are all connecting wirelessly to one wireless access point.  29 of the computers are downloading updates from our internal update server, and since the communication is entirely internal, are not using any of our internet bandwidth.  The 30th computer is attempting to stream a video from YouTube.  Each wireless access point can provide roughly 300Mb of bandwidth to connected clients, so 30 machines would each get 10Mb of bandwidth.  While our 40Mb internet connection may be in use by only the one computer streaming YouTube, it will only effectively have a 10Mb internet connection, due to limitations of the wireless access point that is also serving 29 other clients.  This example shows how this type of problem can arise, but also shows how unlikely it is to occur.  First, in very few cases are a large number of computers in one area accessing non-internet resources (like updates from a server) simultaneously.  Even when they are, our wireless network is designed to provide more than one available access point to all locations in the district, so the lab of 30 computers would likely be connecting to several access points, thus maximizing the bandwidth available to each client.

The other common cause of internet performance issues is problems with or limitations of the website you’re trying to reach.  This is more common than you might think.  Just as we can have problems caused by our ISP, network limitations, or bandwidth limitations, so too can websites and other web services run into those issues.  If Apple releases a new version of OSX, for instance, the servers delivering the software update to customers are likely being contacted by millions of users simultaneously; while a normal update from Apple may be delivered to your computer as fast as your internet connection will allow, it’s very common for servers to slow well below our own 40Mb bandwidth limitations when they’re busy.  In fact, let’s say you were at ADM High School on New Years Eve and were the only one using our internet connection, giving you a full 40Mb all to yourself.  Rather than get a full 40Mb download speed on most websites, you’d find that even then you’d be unlikely to get more than 10Mb or 15Mb speeds when getting content from most public websites, due to restrictions on and limitations of those websites themselves.

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