Abstract: In order to enable nodes with a single protocol switch core to be used in a synchronous transmission network carrying both SDH and SONET traffic then one option is to convert traffic between protocols at the various network nodes. For example, if the network node has a switch core arranged for SONET, then when SDH traffic arrives at that node it can first be converted to SONET before being processed by the switch core and then converted back to SDH again if required. Known methods of converting between SONET and SDH are not suited for use at egress points of network nodes where pointer alignment processes do not occur. A new method of converting between SONET and SDH is described which overcomes these problems by reordering the position of stuff columns.

Abstract: A system comprises a main processor, one or more sub-processors and an event queue apparatus arranged to queue events to be transmitted between the main processor and the sub-processors. The event queue apparatus comprises one or more storage devices arranged to implement a plurality of event queues; and an event queue status indicator, including a respective status component for each event queue. The status components indicate if the respective event queue contains at least one event. The main processor associates a respective priority with each status component and selects to handle an event from the event queue associated with the highest priority of the non-empty event queue(s).

Abstract: A sub-system for forming part of a packet-data communication system for the transmission of data packets which contain media access control addresses and protocol addresses. The sub-system comprises a multiple-port network switch for forwarding data packets in response to an examination of the packets on the basis of the packets protocol addresses, and for performing said examination when a destination address in the packet corresponds to the media access control address of the switch, the switch being arranged for forwarding a packet on the basis of a media access control address therein when the destination address of the packet does not correspond to the media access control address of the switch, said switch including a forwarding database which comprises entries which relate a protocol address with a media access control address and an identification of a particular port of the switch. This switch may perform routing within a local-area network.

Abstract: In order to enable nodes with a single protocol switch core to be used in a synchronous transmission network carrying both SDH and SONET traffic then one option is to convert traffic between protocols at the various network nodes. For example, if the network node has a switch core arranged for SONET, then when SDH traffic arrives at that node it can first be converted to SONET before being processed by the switch core and then converted back to SDH again if required. Known methods of converting between SONET and SDH are not suited for use at egress points of network nodes where pointer alignment processes do not occur. A new method of converting between SONET and SDH is described which overcomes these problems by reordering the position of stuff columns.