Delay, Latency, and Jitter (Linktionary term)

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Delay, Latency, and Jitter

Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

Delay and latency are similar terms that refer to the amount of time it takes a bit to be transmitted from source to destination. Jitter is delay that varies over time. One way to view latency is how long a system holds on to a packet. That system may be a single device like a router, or a complete communication system including routers and links.

Closely related topics include bandwidth and throughput. These are illustrated in Figure D-18. Bandwidth is often used to refer to the data rate of a system, but it more appropriately refers to the width of the frequency band that a system operates in. Data rate and wire speed are better terms when talking about transmitting digital information. The speed of a system is affected by congestion and delays. Throughput refers to the actual measured performance of a system when delay is considered.

Figure 18: See book

Delays are caused by distance, errors and error recovery, congestion, the processing capabilities of systems involved in the transmission, and other factors. Even if you remove these hardware-type delays, you still have the speed-of-light delay. It takes nearly 30 ms to send a bit through a cross-country fiber-optic cable, a delay that can't be eliminated.

Delays of distance (called propagation delays) are especially critical when transmitting data to other countries (especially when you consider all the equipment along the way that adds delay). Delay is also significant with satellite transmissions.

This topic continues in "The Encyclopedia of Networking and Telecommunications" with a discussion of the following:

Delay problems with real-time traffic
Delay problems with transaction processing systems
Problems with variation in delay (jitter)
Causes of delay, including congestion, processing delays, queueing delays, and propagation delays
Survey of TCP performance issues that result in delay
Monitoring and controlling delay (traffic management, traffic shaping, and traffic engineering)
Other solutions to the delay problem, including content distribution architectures, QoS (quality of service), prioritization, and differentiated services.

See the references and links on the related entries page for more information.