ATM Signalling:

The Signalling capability for ATM Networks has to satisfy the following functions.

1. set up, maintain and release ATM virtual channel connections for information transfer.

2. Negotiate the traffic characteristics of a connection(CAC algorithms are considered for these functions.)

Signalling functions may also support multi-connection calls and multi-party calls. Multi-connection call requires the establishment of several connections to set up a composite call comprising various types of traffic like voice,video, image and data. It will also have the capability of not only removing one or more connections from the call but also adding new connections to the existing ones. Thus the network has to correlate the connections of a call. A multi-party call contains several connections between more than two end-users like conferencing calls.

Signalling messages are conveyed out-of band in dedicated signalling virtual channels in broadband networks. There are different types of signalling virtual channels that can be defined at the B-ISDN user-to-network interface. They can be described as follows. 1. Meta-signalling virtual channel is used to establish, check and release point-to-point and selective broadcast signalling virtual channels. It is bidirectional and permanent. 2.Point-to-point signalling channel is allocated to a signalling endpoint only while it is active. These channels are also bidirectional and are used to establish, control and release VCCs to transport user information. In a point-to- multipoint signalling access configuration, meta-signalling is needed for managing the signalling virtual channels.

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