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Align time events in a client server environment Disclosure Number: IPCOM000126912D
Original Publication Date: 2005-Aug-10
Included in the Prior Art Database: 2005-Aug-10
Document File: 2 page(s) / 41K

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improve client server protocol exchanging timestamp as informatin data

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Align time events in a client server environment

This article describes an improvement in a client server protocol when sending timestamp as information data, and it not guarantee that the client and the server have time aligned.

The base protocol is that, for each packet sent from the client to the server, the client includes its current timestamp in the packet. The server match the passed timestamp with its own, and apply the correction to all events sent with the packet.

     This former solution, however, contains a small error due to the transport time between the client and the server (namely, tdelay), and moreover, produce a different correction between two different packets sent from the client.

     The described solution is an enhanchments, providing a more accurate time correction using sent packet history. It also produces a way to avoid correction if the two different host have the system clock synchronized.

     Basically, the idea is to use a moving average of the difference timestamp for each packet to calculate the time difference to be applied to the arrived packet. Using this approach the random latency time that is produced in the transmission of each packet is mitigated, and using an hysteresis function, the applied difference could be the same for every transmitted packet.

Let's make an example, to better understand.

Assume the following convention: tc : the client time when the packet is sent ts : the server time when the packet is received tec : the time of a single event on the client tes: the time of a sing...