Bandwidth Measurement FAQ

Network Speed Problems

In all instances if you believe that your network connection is slow contact your Local IT Support Staff (LITSS) to help solve the problem. If needed, your LITSS will contact Networks and Communications.

What is Bandwidth?

In computer networking bandwidth is referring to the data rate, speed at which information can be moved, of a channel. The channel can be wireless, UTP cabling, a USB cable or anything else that carries information.

How bandwidth is measured?

There are a lot of ways to measure bandwidth, some measurements are very similar and are often confused. Below is a list of the typical units you may encounter. The main thing to note is the difference between the bits and bytes units, they only differ by the capitalisation of the letter B. There is a factor of eight difference between Kbps and KB/s, this is because there is eight bits to a byte. Therefore a 54 Kbps dial-up connection can also be specified as a 6.7 KB/s connection.

Typical Data Rate Units

Typical Connection Speeds

Important Points

The following is a list of factors that affect network bandwidth, it is not an exhaustive list.

1. Network Interface Card (NIC): If you have a 1Gigabit (1000Megabit) NIC in your computer, this does not mean you will get 1 Gigabit per second (Gbps) download speed. This is due to multiple reasons, including:

1. For most areas the ANU network only has 100 Mb connections to the desktop.
2. The 100Mb connection to your desktop is a theoretical limit: You will never get this speed even if you are transferring directly between two computers. Many factors contribute to decreasing the maximum theoretical limit of the cable. Mainly your computers ability to handle such large amounts of data.
3. NIC Driver: Manufacturers produce variable quality drivers, which produce variable performance
4. NIC Manufacturer: Manufacturers produce variable quality NIC hardware. For example the custom NICs that are produced for servers or hardcore gamers offer much better performance then a $10 NIC at the local shops.

2. Resources of your Computer: Your computers processor, memory and hard drive as well as the NIC contribute to how quick your computer can send and receive data. The more powerful your computer (i.e. higher processor speed, more memory, quicker memory) the quicker it can send and receive data.

3. What you are currently doing on the computer: The processor and memory of your computer is needed to send and receive data over the network. If you are running your memory and processor near its limit, expect to see a decrease in your network traffic as well.

For example don't expect to surf ebay as quick as usual if you are simultaneously compiling a program in the background, have itunes playing, your email open and are downloading the latest Security patches off Microsoft’s website.

4. Time of Day: The network infrastructure of the ANU, the ISP that we use to connect to the internet (AARNET) and the internet at large all over the world has a limited capacity. The more users/data (traffic) that is moving across the networks the slower every individuals connection will be.

5. Distance to Server: Data that only has to travel to the ANU Web Server will be nearly instantaneous and will travel entirely over the ANU Network, Networks and Communications has control over this. However if you access a site located on a web server in Darwin then the data can travel over multiple networks (only one of which ANU has control over, its own) and will have delays due to:

1. The distance traveled
2. Capacity, speed and setup of the network infrastructure the data travels through.

For example, accessing a site in London will require an even longer distance and more network infrastructure to travel through then accessing the ANU web server.

6. Speed of the server you are accessing: Two main factors to consider are:

1. Computational Resources of computer i.e. memory and processor: A server is a computer and can only complete so many requests in a period of time, in busy periods some servers may slow down as they cannot keep up with the requested data.
2. Link to Internet: If the server you are accessing only has a 1.5 Mbps upload ADSL link to the internet, it can never upload more then this amount and will typically upload much less as it is required to serve more then just one computer over the world. ANU has 100Mbps (Theoretically) to the desktop but if the server is limited to 1.5 Mbps, this is the maximum speed the data will be downloaded at.

Self Testing Bandwidth

There are multiple bandwidth measuring programs available (a.k.a “Speed Tests” Surf Speed Tests” “Bandwidth Speed Tests” “Download Speed Tests”), some are run directly from the web while others run from your computer.  These programs will give varying results everytime you run them, this can be understood by reviewing the factors under Important Points.

Networks and Communications does not recommend any particular programs to measure your bandwidth. Use of such programs is not disallowed on the ANU Network, however users should be aware that most of these programs download large amounts of information to measure the bandwidth and this is charged to your area.