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January 21
Network Latency

There is something important that I should probably address. The numbers on performance that I usually provide are based on server performance only. They don’t take in account network performance, as everybody’s connection speed and quality is different. I don’t provide those numbers because there are multiple ways to interpret them, however today I’m going to make an exception.

When we monitor performance of an application like Blackboard, each request is actually made up of several parts, each have a specific function, and each attributes to the overall health of the application. Here are the items that we actually monitor to determine the speed of the entire request:

  • Host – the amount of time required for the backend server to process the request, including database or other transactions that occur after the server has started working on it.
  • Network – the amount of time it takes for the information to be transferred between the Browser and the server.
  • SSL – the amount of time the browser and server spend negotiating the secure connection, this is usually low or zero, as once the initial handshake is done, subsequent requests don’t need to do it.

The network latency is important because it can tell us what is going before the server even gets the request, we can determine if certain areas of campus or residential internet providers are having connectivity problems. Some things we can fix, some we can just document so we know what is going on.

Tuesday was a great example of network latency, many people on campus utilized streaming video to watch the Presidential Inauguration from their computer, so many that network slowdowns were seen around campus, as well as with Blackboard and other applications. While I don’t have full reports yet, usually network latency averages around 300 milliseconds, nearly 1/3 of a second. During the Inauguration, we saw network latency on Blackboard go to around 1.2 seconds over a 30 minute period.

MyUK, Exchange, and other systems monitored with the same tools saw increased network latency while bandwidth was being used to deliver the video around campus.


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