Abstract: A system comprises: a representation of a network; a communications requirements file for an application to be executed by a node of said network; and a security policy file defining a security policy for said node of said network. Said files are processed to determine whether said security policy and said communication requirements are compatible.

Abstract: A communications system (40) comprises a first entity (42), a first encryption device (48) and a network (46). The first encryption device (48) is adapted to decrypt, using a first decryption algorithm, data sent from a first destination to said first entity via said network (46). The first encryption device (48) is adapted to pass network metric data concerning at least one route between said first entity and said first destination to said first entity without subjecting said network metric data to said first decryption algorithm.

Abstract: A system comprises: a representation of a network; a communications requirements file for an application to be executed by a node of said network; and a security policy file defining a security policy for said node of said network. Said files are processed to determine whether said security policy and said communication requirements are compatible.

Abstract: A communications system (40) comprises a first entity (42), a first encryption device (48) and a network (46). The first encryption device (48) is adapted to decrypt, using a first decryption algorithm, data sent from a first destination to said first entity via said network (46). The first encryption device (48) is adapted to pass network metric data concerning at least one route between said first entity and said first destination to said first entity without subjecting said network metric data to said first decryption algorithm.

Abstract: In a cell-based transmission protocol such as ATM, a Cyclic Redundancy Check code is used for error detection at a frame level, and a Hamming code is used for error correction at the cell level, to improve error protection, and reduce the need for retransmission. The method can be used as a modification to ATM Adaption Layers.

Abstract: Data packets are transmitted over a communications link in an interleaved manner. The link comprises a series of time-division multiplexed (TDM) frames, each frame comprising a plurality of time slots, a time slot being shorter than a data packet. Data packets are transmitted over a series of the TDM frames, one time slot in each of the series of frames being used to transmit a portion of that data packet. Different ones of the data packets begin in different TDM frames. Received data packets are allocated a modified header for use over the communications link. The modified header has a shorter address than the address in the received packet header and the modified header can be split into a plurality of parts which are distributed across the length of the transmitted packet.

Abstract: Following failure of part of the network, a restoration process is carried out. A restoration route around the failed part is selected, and at least a portion of the capacity of links along the restoration route is allocated. The restoration route may be completed without delay. If it can be optimised subsequently, it will be changed, to eliminate any loops, or to use routes further away from the failed part, to avoid congestion close to the failed part.

Abstract: In a cell-based transmission protocol such as ATM, a Cyclic Redundancy Check code is used for error detection at a frame level, and a Hamming code is used for error correction at the cell level, to improve error protection, and reduce the need for retransmission. The method can be used as a modification to ATM Adaption Layers.

Abstract: For restoration of a network a plurality of possible alternative routes are determined. Messages are passed between nodes along the alternative routes to determine a spare capacity of each link in the alternative routes. An alternative route is selected from the possible alternative routes on the basis of a database of the determined link spare capacities for each of the possible alternative routes, built up at a chooser node at one side of the failed part of the network.