Abstract: A system for controlling traffic in a digital communication network to avoid data loss due to congestion utilizes both credit-based and rate-based traffic control approaches within a common framework, and adjusts the rate at which data is transmitted from a source in accordance with feedback in a form of credit values from a destination reflecting the ability of the network to transmit data and the destination to receive data. In one embodiment, the destination receives the information about network congestion, and, knowing its own capacity to receive more data, generates a credit in the form a numeric value which is fed back to the source so that the source adjusts its transmission rate to avoid data loss due to congestion in the network.

Abstract: A data processor has provision for error recovery by the division of a program into a set of program blocks. The apparatus has a main store and a cache store that preserves the states that have previously been taken up by items of information prior to commencing each block so that the states of the items of information prevailing at the beginning of a block can be restored if required.