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What is this

"connection speed"



Good question! And there isn't just one answer to it. It depends what you want to know. Do you want to know how fast your browser will display a Web site? Or, do you want to know how fast you can download a file? Or simply, you want to know if your modem works as advertised.

Click here for RxTx 3.2 (Description and Help).


The main steps of a connection process...

Here are the 4 big steps that a regular Internet connection must go through:


 1. Dial-Up and PPP phase

This is the process of dialing and logging in to your server (ISP).

How long this takes? From seconds to...a very long time. Usually, less than one minute. It depends primarily on how busy the server is or how many lines it has available. During this phase only short messages are exchanged between your computer and the server. The speed of your modem doesn't really matter.

2. The DNS phase

DNS (Domain Name Search) protocol is utilized to find the IP address associated with the name of the server that you want to connect to. For instance, Your computer starts the DNS by sending the site name in a request to a server located at one of the addresses listed in your Dial-Up Networking settings (Primary and Secondary DNS). From this server, it gets the IP address of the requested name.

How long this process takes? Again, from seconds to...a very long time. Usually, a few seconds. However, once the IP address of a site is found, it is stored in a database in your computer such that successive calls to this site take practically no time. When you close your application (for instance Internet Explorer) the database is deleted.

The DNS messages are relatively short so your modem speed doesn't necessarily play much of a role here.

3. The Connect phase

Once the IP address of the site is found, you need to connect to a particular file residing in this site. For example, if the site displays a Web page, the main HTML file needs to be found. This file will be for example

How long this process takes? Again, from seconds to...a very long time. Usually a few seconds. But the Connect process needs to be repeated for every file listed in the main HTML file of the site. These files contain pictures, text, videos, sound or other elements of the Web page. So, the entire time necessary to connect will depend on the number of files listed in the main HTML file.

The connect phase is usually the most time consuming process when you download a Web page. This is because the files that make up the page reside in computers that are located in different parts of the world and need to handle a huge amount of data. There isn't much one can do to speed up this process. However, some tricks can help (sometimes). Pinging a particular site, enabling the MTUDiscovery feature or selecting a high TTL (Time To Live) number in your Windows PC could minimize the fragmentation of packets and decrease the time necessary to receive data from a remote computer. Unfortunately, there are no guaranties that these tricks will really work.

The Connect process requires relatively short messages so your modem speed doesn't necessarily mater.

4. Downloading files

Well, we can talk now about connection speed. Obviously, the faster your modem, the faster a file will be downloaded. Or is it...? Of course not... If a 2 Mbits (Mega bits) file will be transferred at a rate of 200 Kbps (Kilo bits per second) than you should receive this file in 10 seconds. In reality, you are not the only customer of that server. So you will receive streams of data followed by pauses. During a pause, other customers are being served. Or, it can happen that one or more packets have been routed through a slower server. Or, the required packet size is too large in which case the packet is fragmented in smaller ones. In either case, a slower data rate or a complete pause will occur.

So, when we talk about connection speed we should consider two terms:

1. The modem speed

2. Bandwidth

The modem speed

This is usually given in Kbaud (Kilo bits per second). A 57k modem doesn't necessarily receive (or transmit) 57 Kbps at any given time. Depending on the condition of the line and the type of file transmitted this number can be lower or higher. How high? On good lines, up to 150k. How low ? Usually, 10k to 20k.

For every Byte of data, the Dial-Up modem will use 9 bits. So, you need to divide the number of Kbps by 9 if you want to know the data rate in KB/s. (57 Kbps = 6.33 KB/s).

Compression: All modern modems can compress data and increase the connection speed. The compression is very efficient on ASCII characters and usually can double the modem baud rate. When modem compression is enabled, make sure that the DTE (speed of the serial port where the modem is connected) is set to the maximum (115200 baud for most PC's).

The Bandwidth

Bandwidth is the time average of the data rate (either received or transmitted) expressed in KB/s (Kilo Bytes/second) or Kbps (Kilo bits/second). 1 Byte = 8 bits. This average includes the pauses. The total time necessary to transfer a file is equal to the Size of the file (KB) divided by Bandwidth (KB/s).

On a particular Dial-Up connection for example, you may have instantaneous modem speeds varying from 27 Kbps to 90 Kbps (or, data rates of 3 KB/s to 10 KB/s) but a bandwidth of 1 KB/s depending on the number of pauses.


There may be some confusion when talking about all these terms and numbers. Nevertheless, the bandwidth stands as the most important parameter when defining the performance of a Web server.

When it comes to your modem performance, the instantaneous rates are important. If you see baud rates equal or higher than the listed baud rate of your modem then you know that your modem (and communication line) works properly.


Version 3.2 (new)

Connection speed and bandwidth checker

RxTx measures the data transfer bandwidth between your computer and multiple servers. It works with Dial-Up, Cable or DSL connections.

Bandwidth is measured by downloading one or more HTTP files and averaging the received data rates. You can specify a number of Internet addresses (or files) as they appear on your browser Address bar. The download speed is generally lower for binary files than for text (ASCII) files so you should choose both binary (.jpg, .gif, .exe, .zip) and text (.html, .asp, .txt) files for test.

Note that when you have your modem compression enabled and download the main HTML file of a Web page you'll get the highest bandwidth for that particular site. This is because the file is ASCII and you get the server's attention. As a general rule, the bandwidth for binary files from the same site will be 50% lower.

In addition, RxTx displays in real time instantaneous data rates. The data rates are shown in Kbps (Kilo bits/second) or KB/s (Kilo Bytes/second).

Data Display (Main Window)

The main window shows the received (Rx) and sent (Tx) data graphs. Rx is shown in yellow and Tx is shown in blue. The caption bar shows the maximum data rate (either Rx or Tx) displayed within the window.

To change the units (KB/s or Kbps) right click anywhere inside the main window and then select Options from the menu displayed.

To find out a particular value of a point from the graph left click and drag across that point. The Rx, Tx values will be displayed on the caption bar. When you release the mouse the average value of the marked region will be displayed.

Menu Controls (NetStat Window)

To access the NetStat window right click on the Main Window client area.

Start: starts measuring the connection bandwidth by downloading specified file(s). You can stop the download at any time however, it is good to have at least 20 seconds of download.

File: displays the URL's of the files to download. You must have Notepad.exe located in Windows directory. ***END*** terminates the reading.

Proxy Setup: opens a dialog box for entering the IP address and HTTP port of your proxy.

BrowserPath: opens a dialog box for entering the path of your browser.

IpStatistics: shows IP, TCP, UDP and ICMP statistics that may or may not be of any interest to you.

Adapter: shows the network adapters installed in your PC. If "0" is entered in the Adapter box (under Options) all the adapter interfaces are shown. Otherwise, only the adapter designated by the Index number entered in the Adapter box is shown.

Note: When you first run NetDoc, you should look at all the adapters and select the one that you are interested. A particular adapter is designeted by its Index number. If no adapter is specified (0 index), the program will select the last active TCP/IP adapter in the list.

Stop: stops the bandwidth check.