DIGITAL COMMUNICATIONS SYSTEM

摘要

In an ATM network a flexible AAL1 processor is connected to a similar AAL1 processor by a virtual circuit. This virtual circuit has nx64kb/s capacity wherein each 64kb/s channel or a Px64kb/s subset of the capacity can be used for a separate call. The virtual circuit behaves similarly to trunk groups within present day digital networks and it is therefore termed a Virtual Trunk Group. Many Virtual Trunk Groups can be connected between the same two endpoints and contained within a virtual path thus forming a Virtual Route. The network is provided with a mechanism which allows the nx64kb/s capacity to be changed by a managed process which ensures that established calls are not affected by the change of capacity. This change of capacity is performed in such a way that the clock systems of the two AAL1 processors are able to behave in the normal manner for synchronised or plesiochronous switching networks without incurring additional frame slips in the AAL1 data stream. Frame slips due to the behaviour of the clock systems are still processed in the normal manner.