Call Admission Control (CAC) prevents oversubscription of
VoIP
Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...
networks. CAC is used in the call set-up phase and applies to real-time media traffic as opposed to data traffic. CAC mechanisms complement and are distinct from the capabilities of
quality of service
Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...
tools to protect voice traffic from the negative effects of other voice traffic and to keep excess voice traffic off the network. Since it averts voice traffic congestion, it is a ''preventive''
Congestion Control
Network congestion in data networking and queueing theory is the reduced quality of service that occurs when a network node or link is carrying more data than it can handle. Typical effects include queueing delay, packet loss or the blocking of ...
Procedure. It ensures that there is enough bandwidth for authorized flows.
Integrated Services with
RSVP
RSVP is an initialism derived from the French phrase ''Répondez s'il vous plaît'', literally meaning "Respond, if you please", or just "Please respond", to require confirmation of an invitation. The initialism "RSVP" is no longer used much in ...
(which reserve resources for the flow of packets through the network) using controlled-load service ensures that a call cannot be set up if it cannot be supported. CAC rejects calls when either there is insufficient CPU processing power, the upstream and downstream traffic exceeds prespecified thresholds, or the number of calls being handled exceeds a specified limit.
''
Connection Admission Control
Connection may refer to:
Mathematics
* Connection (algebraic framework)
*Connection (mathematics), a way of specifying a derivative of a geometrical object along a vector field on a manifold
* Connection (affine bundle)
* Connection (composite b ...
(CAC)'' can be used to prevent congestion in connection-oriented protocols such as
ATM. In that context, there are several schemes available.
[Call admission control schemes: a review. HG Perros, KM Elsayed, N Inc - IEEE Communications Magazine, 1996 - comsoc.org] However, VoIP differs in that it uses
RTP,
UDP and
IP, all of which are
connectionless
Connectionless communication, often referred to as CL-mode communication,Information Processing Systems - Open Systems Interconnection, "Transport Service Definition - Addendum 1: Connectionless-mode Transmission", International Organization for ...
protocols.
References
{{reflist
External links
* https://web.archive.org/web/20050519224329/http://www.bytbredbandsdelare.nu/cac.pdf
VoIP protocols