Abb Research Ltd.

Ontime Networks As

Øyvind Holmeide

Svein Johannessen

Christoffer Apneseth

Tor Skeie

Trond Lokstad

Digital communications receive signals from the network tap represent 'tapped' data. The tapped data is forwarded to a time stamp module. The time stamp module generates a time stamp and inserts the time stamp in each packet body. The time stamp represents a 'time' when data packet content is considered to be generated at a sending node from which the tapped data originates. A packet time-stamped in this manner is then forwarded to one or more receivers, such as the recorder for additional processing. One such processing may be a performance measurement based at least in part on the time stamp that, as described, represents the time at which data packet content is considered to have been generated by the sending node. The network tap may be filterable, and either copper-based or a fiber tap.

Time-stamping data packets in a network tap element

The present invention relates to a method for identifying inaccurate time measurements in a local area network. The local area network comprises a sending device (), such as a time client, a destination device (), such as a timeserver, and a switching device and/or a store-and-forward device (). A time request packet () is rejected if it arrives at the time client or timeserver within a given or calculated minimum distance from the preceding network packet. The time request packet () is also rejected if it falls outside a set of calculated error limits based on a set of estimates. Those estimates are kept in the time client memory and updated according to a given set of rules.

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Oslo, Norway

Øyvind Holmeide