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Network delay is the time it takes for a packet to travel from one device to another in a packet switched network. In a circuit switched network, it only includes travel time. Network delay includes transmission, propagation, processing, and queue delays. Excessive delay can cause packet jitter and loss, resulting in garbled phone calls and slow web page retrieval. Network designers use tools to troubleshoot lag issues. Understanding network delay is crucial as networks continue to grow in speed and capacity.
When two devices communicate with each other using a packet switched network, it takes a certain amount of time for information to be generated by one device, travel to the other device, and be received by the second device. The total time it takes for this block of information, commonly called a packet, to travel from one end to the other is called the network delay. There is another type of telecommunications network called a circuit switched network. In a circuit switched network, network delay is considered only the travel time from one device to another, excluding output and draw times.
A typical computer network is a packet switched network, so when talking about computer networks, network delay takes all three of these delays into account. They are more formally called transmission or serialization delay, propagation delay and processing delay. Some network devices, such as routers and switches, also introduce additional types of delays into a network, such as queue delays. These additional delays, if they occur, are included in the total network delay time.
In the field of computer networking and network engineering, network delay is an important consideration. Excessive variable delay can cause unwanted side effects such as packet jitter and packet loss. Variation in packet delay, or jitter, creates problems like garbled phone calls and shaky video playback. Packet loss can cause dropped phone calls, longer download times, and slow web page retrieval.
Network lag can be caused by many things, including improper network design, the natural characteristics of different media, excessive network traffic, and malfunctioning or misconfigured devices. Network designers strive to reduce the causes of delays. They use utilities and tools like ping, traceroute, cable testers, and network analysis software to troubleshoot lag issues and what could be causing them. Most operating systems allow a person to test the delay by issuing ping or traceroute commands from a command prompt.
As networks continue to grow in speed and capacity, it becomes increasingly important to understand how long information takes to travel from one point to another and where the delays occur. Information traveling across networks is mixed together from multiple sources and separated many times as it travels. Phone calls, web pages, downloads and many other types of traffic are mixed and separated repeatedly. If network delay is not minimized, more and more information could be lost in transit as network loads increase and congestion builds.
