Agilent Technologies, Inc.

Brian Woodroffe

Simon Love

Patrick Goldsack

James W Davis

Jeremy Peter William Brown

Service detail records (SDRs) are generated for at least two layers in a stack of protocols used in a communications network, where protocol data units (PDUs) for a lower-level protocol encapsulate PDUs for a higher-level protocol. SDRs for the higher-level protocol include pointers to SDRs for connections at the lower level which encapsulate PDUs from which the higher-level SDRs were generated.

Service detail records for layered communications protocols

Data cells traversing an Asynchronous Transfer Mode (ATM) network ( ) are passively monitored by probes at two spaced points ( ). A filtering characteristic is applied to select cells comparatively infrequently, and timestamps or sequence numbers (or both) for the cells selected at each point are forwarded to a correlator ( ). The correlator identifies similarities in the temporal patterns of intervals between timestamps received from each probe, and uses these similarities to identify and correlate timestamps relating to occurrence of the same cell at the two monitored points. The correlated timestamps are used to determine parameters indicative of the performance of the network, such as one-way delay, variation in that delay, and rate of cell loss.

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Brian Woodroffe