TcpSpeed Online Help
TcpSpeed is the first public utility which measures the bandwidth
of any TCP/IP connection. This is useful for Internet users, as
well as for users of an internal TCP/IP corporate network.
No installation routine has been provided since it's so easy to
do a manual installation. (Plus, it helps to keep down the size
of the file that you must download.) Here's how to install TcpSpeed:
- Get the TCPSPEED.ZIP file (or TCPSPD.ZIP on CompuServe).
- Unzip the files into the desired directory. If you are running
a Windows 95 system we would recommend that you create a directory
called C:\Program Files\Maximized Software\TcpSpeed.
- After you have unzipped the files you can delete TCPSPEED.ZIP.
- That's all! You're ready to run TCPSPEED. You may want to
drag the executable to your Windows 95 Start menu (or put it somewhere
deeper in the menu), or create an icon in the Windows 3.1 Program
To uninstall TcpSpeed, simply delete the following files:
- TCPSPEED.INI (in your Windows directory)
There's a small bug!
Oops! There's a small bug in TcpSpeed 1.01. The bug is that if the
first host that you try to connect to doesn't work, then subsequent
hosts will not work at all.
The workaround is to make sure that you always meter a known, reliable
host first, then try other hosts. Otherwise, you will need to exit
TcpSpeed and then restart it in order to reset it.
In the world of TCP/IP, the word host just refers to a
computer. For example, when you are connected to the Internet
your computer is considered to be a host. TcpSpeed measures the
throughput between two hosts on the Internet: your computer (host),
and another computer that you specify.
The most challenging part of using TcpSpeed is finding another
host which can be metered. For more information see the section
below titled Finding A Host To Meter.
Once you've found a host to meter, TcpSpeed will measure the throughput
between the two computers. If you are connecting to a host that
is far away then the data will have to travel a much longer distance,
and will most likely travel along many different segments of the
Internet. It is important to note that the throughput will
always be limited by the slowest segment! The slowest
segment effectively acts as a choking point, and you will never
get higher throughput than that link allows. (It's like a pipe
carrying water.) For home users, it is likely that the slowest
link will be their modem.
Keep in mind that using TcpSpeed sucks up all available
bandwidth, so use it sparingly. That's why there is a
12-second time limit built in. That also is the reason that we
do not provide a list of suggested sites to meter: because if
we did then these sites would be constantly bombarded with TcpSpeed
activity, thus using up all of their bandwidth (not cool!)
as well as increasing the chance that your readings won't be as
accurate because someone else may also be connecting to the same
host. So please try to find new and different hosts to meter so
that the common hosts don't get overloaded. And please don't over-use
TcpSpeed, since too many simultaneous high-throughput users can
adversely affect the performance of the Internet.
How To Use TcpSpeed
Using TcpSpeed is very simple. Just make sure that you have a
live connection to the Internet, then follow these steps:
- Type the name of a host that you want to meter into the Host
Name edit field.
- Click on the Start Metering button, or just press Enter.
- TcpSpeed will attempt to connect to this host and meter the
bandwidth between your computer and the other host. If it cannot
connect then you will see an error message. If it can connect,
then TcpSpeed will begin to measure the throughput between the
- After 12 seconds have passed the test run will be stopped.
You may also stop it at any point before the 12 seconds have elapsed.
If you want to operate TcpSpeed through a firewall, your firewall needs
to pass TCP packets on ports 62901 and 19.
Understanding The Statistics
TcpSpeed performs relatively simple math: it divides the total
number of bytes received by the time it took to receive them.
This is the basis for all of its calculations. The following three
numbers are provided:
- Avg Kbits/sec: This indicates how many thousands of
bits were transferred per second. This number is similar to the
speed ratings for modem. The user of a 14.4 modem might expect
to see a number like 14 or 15. The user of an ISDN line might
see numbers as high as 128. Higher numbers indicate higher throughput.
- (max): This is the highest value that Avg Kbits/sec
(above) has had during the current test run. You will see it change
as new high values are reached.
- Avg Bytes/sec: This reports the average number of bytes
received per second during the test run.
It is important to note that the statistics are updated only when
data is being transferred. Thus, if the data stream pauses for
a while the statistics won't be updated. This can lead to potentially
misleading numbers unless you understand the numbers. For example,
consider the case where as soon as you start the test 100 bytes
are transferred immediately. The window will update to show 100
bytes/sec. Then if nothing else happens during the rest of the
test, the window will not update again, so when the test is done
it will look like an average of 100 bytes/sec bandwidth. But in
fact, that number is only valid up until the point that it stopped
receiving data. If you were to average the bytes over the total
time then you would get a number more like: 100 bytes / 12 seconds
= 8 bytes/sec.
In general, this shouldn't be a problem for most hosts that you
meter, since they usually have pretty decent throughput.
Reading The Graph
The blue bar indicates the amount of throughput currently measured.
At the far right of the graph is the maximum Avg Kbits/sec
value that has happened during this trial run, and the blue bar
is filled in proportion to the current value of Avg Kbits/sec.
Higher numbers are better because they indicate higher throughput.
If you get a situation where the maximum value is very high but
the blue bar drops well below the maximum value, then that means
that the packet traffic between the computers is "bursty".
Finding A Host To Meter
Not every computer on the Internet can be metered. There's no
good way to find hosts which can be metered without just trying
some common locations. Here are some suggestions to help you on
- When entering a host name, do not include any leading protocol
string, such as http://. For example, if you are curious
about the bandwidth coming from Netscape's web site (http://home.netscape.com),
you would specify just the host name (home.netscape.com) instead of
the web site's full url (http://home.netscape.com). (Please note
that this is only an example; the Netscape home page cannot be
- The first host that you should try is your Internet access
provider. For example, if you are a home user and have an Internet
account with an access provider whose domain is acme.net then
you might want to try metering the hosts acme.net, www.acme.net,
- If you are a user connected to an internal LAN, try connecting
to your main server. For example, server.company.com.
- Try a local university. These often have host names like www.uschool.edu.
- Try a university located far away. This often provides a good
comparison of how much longer it takes data to move across long
- Popular web sites and FTP sites can often be metered. Also
try the servers of popular computer companies.
- If you know of a domain such as acme.net but find that
it cannot be metered, don't forget to try other derivatives of
that name, such as www.acme.net and ftp.acme.net.
Most of these suggestions are available from the Help / Finding
Hosts menu command.
If you specify a host name which doesn't exist, it may look like
your computer is hung for up to 30 seconds (while your TCP/IP
stack figures out that the host doesn't exist). If this happens,
just wait a while and control will be returned to you soon.
Modem Compression And High Numbers
Unfortunately, the data that TcpSpeed uses to measure bandwidth
is highly compressible. In fact, the compression rate may go as
high as 98%! Therefore, users connected to the Internet via a
modem with compression (V.42bis, MNP, etc) may see bandwidth numbers
that look much too high. For example, one home user with a 14.4
modem reported an Avg Kbits/sec ranging from 20 to 30!
At this point the best solution for this problem is to disable
modem compression in your TCP/IP stack's dialer program, and then
try TcpSpeed while no compression is going on.
We are looking for ways to improve the situation, and will let
everyone on our mailing list know if we put out any new solutions.
TcpSpeed is freeware, but we do request that you register your
copy after 10 uses. You can register at any time by choosing the
File / Register command. If you have not registered after 10 uses
then the registration dialog box will pop up the next time you
Please note when registering that you are asked whether
or not you would like to be on our mailing list. If you decide
to be on the list then we will keep you informed of major events
at Maximized Software that might be of interest to you. But
we promise not to bombard you with junk mail!
The Help / About Dialog Box
TcpSpeed provides a Help / About menu command. If you choose this
menu command you will discover that there are two links at the
bottom of the dialog box. Clicking on them with your mouse will
have your copy of Netscape jump to the Maximized Software web
site, or will pop up a Netscape mail window so that you can send
e-mail to us.
This feature requires you to be running Netscape Navigator
1.1 or greater at the time that you click on the link!
Host Cannot Be Metered
This message indicates that the specified host was found on the
Internet, but is not properly configured to allow you to measure
the bandwidth between it and your computer. There's nothing that
you can do about this problem; you must simply try to find another host
This vague error message indicates that the specified host name
does not exist. There's no way to fix this; you must simply try
to find another host to meter.
Other error message
If any other error message appears in the Status field, it will
be an error returned by your Winsock implementation (i.e., TCP/IP
stack). You may find the message useful, but there may be nothing
that you can do to solve the problem. The message is provided
merely for your information.