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Diagnosing Slow Connections
All communication across a network
is broken into packets before sending and is reassembled at the receiving end.
Let's say we are sending a 100 page
letter to someone and his mailslot is only big enough for one page at a time. So we have
to send each page in its own envelope with its own addressing and stamp. Several things
can happen:
All the envelopes are delivered
without mishap (giggle).
None of the envelopes are
delivered (either you or the receiver
or both are not online or your ISP has router difficulty or Atlanta
has been hit in a pre-emptive tactical nuclear strike).
Some of the envelopes are
delivered.
If it is the last case, and it
usually is, success depends on how many of the envelopes are delivered. Some protocols
will try to resend lost envelopes but in the end, there will usually be some missing
information. If you try to read a book with a few missing pages, you still get the
gist of the story as long as the missing pages are not consecutive and don't include
critical plot changes. In the same way, the web server, ftp server or your local computer
can recover from some missing packets to finish your upload or download.
If say, 95% of the packets arrive
intact, the receiving computer can assume the missing material from context.
For example:
She _ells seashe_l_ by the _eashor_.
Is easily translated into:
She sells seashells by the
seashore.
If say, only 80% of the packets
arrive safely, there is not enough to put the whole message back together, this:
_he ___ls __ashe___ b_ the __asho__
is not enough to work with.
If the receiver sees that it has
received less than 80% of say, the first 20% of the message:
__e se___ s_a___
it gives up early and sends a
message like "blocking call canceled" or "connection failed".
Web browsers will give slightly
different error messages.
Missing or delayed packets
will be the cause of 90% percent of your connection difficulty.
The first step in diagnosing
connection problems is to run a traceroute. This will help to determine what path your
connection takes across the Internet to reach our servers. The traceroute tool is not
intended to gauge your Internet connection as a whole but to show the specific path you
take to a specific location. If you have a Windows95 or WindowsNT computer, you can use
the built-in traceroute program to do this.
Macintosh users can get a free traceroute utility from allmacintosh.com
Click on the 'start' button and go to 'programs'. Choose 'MS-DOS prompt'
('Command Prompt' in NT) and at the 'c:\windows>' prompt, type:
tracert yourdomainname.com
You will be presented with a
string of numbers representing the connect times of three packets sent to the next server
in line through which you must pass on your way to our server. That server then
sends three packets to the next server in line and reports those times back to you. If you
see an asterisk in place of a connect time, this means that packet was placed on a network
wire at the same time another server placed a packet on the wire and they overwrote each
other (commonly called a data collision). This is indicative of heavy traffic on that
network and three asterisks on the same line mean that may be a dead connection. In this
case we suggest logging off and logging back on to your ISP to see if you can get a
different connect route. If you see long connect times
(consistently in excess of 400ms), the server on that "hop" may be busy
servicing other packets . This traceroute is only a snapshot of network traffic at that
moment in time. It should be run several times to determine the "trends" of the
traffic. To save it to a file for future reference, type:
tracert yourdomainname.com > C:\trace.txt
This will create a file in the root
directory of your hard drive named 'trace.txt' that you can then view with 'notepad'. Any
subsequent traces can be appended to the trace.txt file with:
tracert yourdomainname.com >> C:\trace.txt
The next step is to determine the path that the server's packets take to you. You can
connect to your site via the built-in Windows95 telnet program. Our telnet tutorial explains the steps
(WindowsNT has the same Telnet program built-in).
Once you are at the telnet prompt on the server, type:
traceroute 216.122.20.185
The number above should be the IP address of your current connection to the InterNet. If
no number appears, our server was unable to determine your addresss and you will need to
contact your ISP or network administrator.
The results of these server side traceroutes can be cut and pasted into a local file via
notepad.exe or this command will send the results to you via email:
traceroute 216.122.20.185 | mail you@yourdomain.com
The symbol between the the IP
address and "mail" above is known as "the pipe" and should be above
the backslash on your keyboard.
If looking at the results of these
traceroutes, both to and from the server does not yield any obvious answers regarding your
connection, email them to us and we will investigate further. If the results point to
specific traffic congestion somewhere between you and the sever, logging off your Internet
connection and reconnecting may help. This may cause your ISP to assign you a different
temporary local IP address which may take a different path to our server.
Shopping for ISP's should be
done using the traceroute tool. Many ISP's offer free evaluation periods during which you
may monitor the connection reliability with this tool. Remember
to run the trace several times to get a feel for the "trend" of the traffic.
For a comprehensive modem connection
trouble-shooting faq, click here.
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