ASYNCHRONOUS ADAPTIVE SWITCHING

The structure of digital integrated service networks may be based on using either discrete channel-switching (CS) or packet switching (PS) networks together with their corresponding modifications, or hybrid networks, which combine both switching methods. Adaptive switching (AS) [1, 2] involves a class of hybrid switching methods in which the transmission mode with reservation of circuit throughput capacity (CS mode) is integrated with a transmission mode without throughput capacity reservation (PS mode). AS has the following features: adaptive redistribution of network circuit throughput capacity between the CS and PS modes depending on the load at any instant; the potential for filling the pauses between messages in the connections which have been established during CS and the data of the PS mode. In the synchronous AS mode, a two-way threshold shifting should be provided between time intervals of a frame during CS and PS, as well as the use in the CS mode of temporarily free time intervals (the pauses between messages), which were assigned for connections managed using CS. This article considers a modification of AS, which is intended to simplify implementation of the switching process due to the transition from synchronous transmission of fixed length frames to asynchronous transmission of variable length frames. In this case the concept of "asynchronous transmission" relates only to transmission of frames, but not characters, which may be transmitted both in synchronous and in an asynchronous (start-stop) mode. This modification is based on the methods of transmission with alternating CS and PS mode frames [3]. Asynchronous transmission of frames is normally used with CS and provides a number of positive properties, including a high efficiency of circuit throughput capacity utilization. The main drawback of such a mode is the dependence of the delay in packet transmission on the network load and the absence of an upper limit on packet delay.