Slow Web Site Performance from Only One Location
Provided by: John Litchfield, Database Analyst
Why Does a Web Site Perform Slowly from One Location?
Have you ever experienced a case where a particular offsite web server
delivers a painfully slow response when you access it from your work
network? You may have already attempted to troubleshoot this issue by
assessing the web server itself, only to unsuccessfully pinpoint any helpful
information or indication that this server is having any technical issues.
Even more bizarre, the web site delivers a “lightening fast” response
when accessed from other locations like your home. “Hmmm…it must be a
problem with my network at work”, you start to think. But after loading
other websites (from work), you notice that these other websites load
perfectly fast. You then (again) attempt to access the problematic offsite
web server from work, but again it still takes forever to load, confirming
the original issue.
At first glance, these symptoms appear to conflict with each other. Could
there be an issue with the particular route being used for data transmission
between these two sites? The answer is yes indeed!
Problems Associated with Routing
A slow response from a website or web server indicates data packet loss.
The larger the number or percentage of packets that are lost during a
transmission, the slower the response is from the server that you are
accessing. How does one troubleshoot or fix a problem like this?
Step 1: Determine the Actual Route Using Tracert
The first step for determining data packet loss is documenting the actual route
being taken (that is, which routers are currently responsible
for the data packet transmission). There is a native Microsoft Windows
command entitled “tracert” that you can use. This command returns
a list of the routers and router locations that are used for the
data packet transmission. Simply execute this command using any Windows
computer system from your site and append the web server IP address as
the parameter. For example:
“22.214.171.124” is the IP address of your web server.
is an example of a sample output using tracert:
From the screenshot above we can see the IP
address of each router that takes a part in the data packet
Step 2: Use Windows Ping
The second step is to use the Windows Ping command to isolate any
routers that may be responsible for packet loss. Packet loss manifests
itself in a sporadic nature. On a random basis, some
data packets are successfully transmitted while others are not. We
can use the ping command to send an assortment of test packets and
measure the percentage of successful transmissions. The larger the number of test packets being
transmitted, the greater the probability that there is packet loss
during your test. It also follows that the larger the packet size transmitted, the greater the
probability that there is packet loss. The ping command is executed in the following manner:
C:\>ping –n 25 -1 500 126.96.36.199
The statement above is an instruction to
send 25 data packets, each 500 bytes in size to the IP address of
“188.8.131.52”. In most cases, a byte size of 500 being transmitted
25 times to a given router is significant enough to discover data packet
transmission problems (or packet loss) if there is in fact a problem.
The screenshot below illustrates an actual
case where data packet loss was discovered by using the ping command. There is an 8% loss of data in this case.
Final Step: Notify Responsible Parties
If you isolate the issue to one or more routers, you need to notify the responsible parties. In most cases, this is your ISP. A simple explanation of your test results with
screenshots is very helpful to them. Be sure to include your tracert report as well as your ping tests.
One last final note: You may want to bear in mind that the results of your ping
tests could be time dependent based on the rate of other traffic passing
through these public routers. In cases like this, you might benefit from the
implementation of various tests at different times of the day or evening since
the time periods of higher traffic will return a higher rate of data packet loss
during transmission when there is a problem.
Special thanks to David O’Leary of Better World Telecom for helping us to
diagnose and resolve this issue
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