Connection Admission Control

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What Does Connection Admission Control Mean?

Connection admission control (CAC) is a set of actions and permissions in network communication that identifies where the connection is permitted on the basis of network ability. This designed set of network actions is initiated during the call setup or when calls are reconnected. It is based on a simple algorithm used to discriminate the incoming or outgoing network traffic. CAC is also used to decide which traffic should be allowed or rejected by a specific network. CAC is most often used in ATM networks.


Also known as call admission control.

Techopedia Explains Connection Admission Control

In terms of communication, the existence of CAC is common, especially in network-oriented connections (CAC does not provide any service to connectionless networks). In addition, in connection-oriented networks, CAC plays an important role, particularly for congestion control.

The basic role of connection admission control in connection-oriented networks is to decide whether there are enough free system resources available before establishing a new connection. An end-to-end connection is only established when the availability of free resources is assured.

CAC performs the following two operations while establishing a connection:

  1. It establishes a connection when resources are free and available.
  2. If the connection is rejected in the absence of free/available resources, a notification is sent back to the originator or requester of the call or connection.

The following factors are to be considered when establishing or requesting a connection:

  • The type of service required
  • Traffic parameters (source traffic parameters are analyzed)
  • Both directions request their required QoS, which is also considered when establishing a connection.


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Margaret Rouse
Senior Editor
Margaret Rouse
Senior Editor

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.