What Is Network Bandwidth?
Bandwidth is the primary measure of computer network speed. Virtually everyone knows the bandwidth rating of their modem or their Internet service that is prominently advertised on network products sold today.In networking, bandwidth represents the overall capacity of the connection. The greater the capacity, the more likely that better performance will result. Bandwidth is the amount of data that passes through a network connection over time as measured in bps.
Bandwidth can refer to both actual and theoretical throughput, and it is important to distinguish between the two. For example, a standard dialup modem supports 56 Kbps of peak bandwidth, but due to physical limitations of telephone lines and other factors, a dialup connection cannot support more than 53 Kbps of bandwidth (about 10% less than maximum) in practice. Likewise a traditional Ethernet network theoretically supports 100 Mbps of bandwidth, but this maximum amount cannot reasonably be achieved due to overhead in the computer hardware and operating systems.
Broadband and Other High Bandwidth Connections
The term high bandwidth is sometimes used to distinguish faster broadband Internet connections from traditional dialup or cellular network speeds. Definitions vary, but high bandwidth connections generally support data rates of minimum 64 Kbps (and usually 300 Kbps or higher). Broadband is just one type of high bandwidth network communication method.Measuring Network Bandwidth
Numerous tools exist for administrators to measure the bandwidth of network connections. On LANs (local area networks), these tools include netperf and ttcp. On the Internet, numerous bandwidth / speed test programs exist, most available for free online use.Even with these tools at your disposal, bandwidth utilization is difficult to measure precisely as it varies over time depending on the configuration of hardware and characteristics of software applications including how they are being used.
What Is Network Latency?
Bandwidth is just one element of what a person perceives as the speed of a network. Latency is another element that contributes to network speed. The term latency refers to any of several kinds of delays typically incurred in processing of network data. A so-called low latency network connection is one that generally experiences small delay times, while a high latency connection generally suffers from long delays.Latency vs. Bandwidth
Although the theoretical peak bandwidth of a network connection is fixed according to the technology used, the actual bandwidth you will obtain varies over time and is affected by high latencies. Excessive latency creates bottlenecks that prevent data from filling the network pipe, thus decreasing effective bandwidth. The impact of latency on network bandwidth can be temporary (lasting a few seconds) or persistent (constant) depending on the source of the delays.Latency of Satellite Internet Service
Satellite Internet service illustrates the difference between latency and bandwidth on computer networks. Satellite Internet connections possess both high bandwidth and high latency. When loading a Web page, for example, most satellite users can observe a noticeable delay from the time they enter a Web address to the time the page begins loading. This high latency is due primarily to propagation delay as the request message travels at the speed of light to the distant satellite station and back to the home network. Once the messages arrive on Earth, however, the page loads quickly like on other high-bandwidth Internet connections (DSL or cable).Besides propagation delays, latency also may also involve transmission delays (properties of the physical medium) and processing delays (such as passing through proxy servers or making network hops on the Internet).
Measuring Network Latency
Network tools like ping tests and traceroute measure latency by determining the time it takes a given network packet to travel from source to destination and back, the so-called round-trip time. Round-trip time is not the only way to specify latency, but it is the most common.On DSL or cable Internet connections, latencies of less than 100 milliseconds (ms) are typical and less than 25 ms desired. Satellite Internet connections, on the other hand, average 500 ms or higher latency.
