MECHANISM FOR DISPATCHING DATA UNITS VIA A TELECOMMUNICATIONS NETWORK

摘要

A dispatch mechanism is provided for dispatching data units, (e.g. datagrams or packets) divided into one or more fragments, via a telecommunications network. T he dispatch mechanism includes a queue for queuing fragments for transmission. It f urther includes a queue controller operable when a fill level of the queue exceeds a th reshold value to discard fragments of data units for which a fragment has not already be en queued and to add to the queue fragments of data units for which a fragment has already been queued. The dispatch mechanism maintains a record of data units which are t o be transmitted (that is when one fragment of the data unit has already been passed for despatch) and a record of data units which are to be dropped (that is data units for which a fragment has already been dropped). The dispatch mechanism enables more effect ive use of network capacity by reducing the possibility of incomplete data units bei ng transmitted over the network. In other words, where one data unit fragment is dr opped, a mechanism ensures that all remaining fragments of that data unit are dropped. Also, where one data unit fragment has been sent, the mechanism ensures that all other fragments for that data unit are sent, irrespective of the fill level of the out put queue when a data fragment for transmission is processed.