Measuring the speed of a computer network can get complicated, but ultimately what matters to most people is how well the connection responds when trying to accomplish some task. Just how fast or slow a network needs to be will depend on how you use it. In general, as more devices and people share a network, the better its performance (measured in terms of bandwidth and latency) must be to support the overall load.
Web Surfing Speeds
Basic Web surfing can be done over any speed of connection, including very slow dial-up internet or phone links. The time required to load a web page increases significantly on low-speed connections, however. Broadband internet connections of 512 Kbps or higher support web surfing adequately, although higher speed connections help with pages that have video and other rich content.
Besides network bandwidth, web surfing is also sensitive to network latency. Web surfing over satellite internet connections, for example, takes longer than for wired broadband internet services offering the same bandwidth, due to the high latency of satellite.
Email and IM Speeds
Sending text over computer networks requires minimal bandwidth. Even old, slow dial-up Internet connections adequately support instant messaging and Web-based email. However, large attachments sent through email or IM transfer slowly over lower-speed connections. A one megabyte (MB) attachment sent over dial-up may take 10 minutes or more to transfer across the connection, while the same attachment can be sent over a good broadband link in only a few seconds.
Television and Movie Streaming Speeds
Video streams utilize more or less network bandwidth based on resolution and frame rate of the content being viewed along with the codec technology used to compress and decode the individual frames. Standard definition television, for example, requires 3.5 Mbps on average, while DVD movie quality streaming requires up to 9.8 Mbps. High-definition video television typically requires 10-15 Mbps and Blu-ray video up to 40 Mbps. The actual bit rate of a given video fluctuates up and down over time based on the content; movies with complex imagery and greater movement require relatively more bandwidth.
Video Conferencing Speeds
Required network speeds for video conferencing are similar to television, except that video conferencing products offer lower resolution and quality options that can reduce the bandwidth requirements considerably. Personal conferencing products like Apple iChat, for example, require 900 Kbps (0.9 Mbps) for a two-person video session. Corporate video conferencing products utilize more bandwidth up to standard definition TV requirements (3-4 Mbps), and three- and four-way sessions also increase the speed requirements further.
Internet Radio (Audio Streaming) Speeds
Compared to video, audio streaming requires much less network bandwidth. High-quality Internet radio typically broadcasts at 128 Kbps, while podcast or music clip playback requires no more than 320 Kbps.
Online Gaming Speeds
Online games utilize widely varying amounts of network bandwidth depending on the type of game on how it was developed. Games with fast motion (like first-person shooters and racing titles) tend to require more bandwidth than simulation and arcade games that use relatively simpler graphics. Any modern broadband or home network connection offers sufficient bandwidth for online gaming.
Online gaming typically requires low-latency network connections in addition to sufficient bandwidth. Interactive games running on a network with round-trip latency greater than about 100 milliseconds tend to suffer from noticeable lag. The exact amount of lag that's acceptable depends on the perception of individual players and also the type of game. First-person shooters, for example, generally require the lowest network latencies.