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Techniques for improved clock offset measuring

A clock offset and time stamp technology, applied in the network field, can solve problems such as difficult to modify and expensive

Inactive Publication Date: 2012-07-18
INT BUSINESS MASCH CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, a hardware implementation as in IEEE 1588 is more expensive and more difficult to modify than a software implementation

Method used

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  • Techniques for improved clock offset measuring
  • Techniques for improved clock offset measuring
  • Techniques for improved clock offset measuring

Examples

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Embodiment Construction

[0020] In one illustrative embodiment, a new technique for clock skew measurement is disclosed that uses a series of "ping pong" exchanges that reduce clock skew to an absolute minimum, where each The exchange involves a single byte that is different at each exchange (eg, decrementing the remaining message count), and can be used to determine whether that single byte is the last exchange in the series. The network nodes on each side of the exchange privately record the arrival and departure timestamps, and at the end of the exchange, return the collected timestamps to the other side (for one of the network nodes, e.g. node or two nodes). In one embodiment, a protocol implementation ensures that each side of the byte exchange knows whether another packet is still expected after a timeout, and that there can only be one such delayed packet. This greatly simplifies timeout recovery and eliminates the need to re-initialize the link after a timeout due to non-determinism (although...

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Abstract

In an exemplary aspect, method, apparatus, and program products are disclosed suitable for clock offset determination. One method includes performing a number of exchanges of at least single bytes with another network node, where values of the single bytes are different for the exchanges. The method also includes capturing and storing timestamps for each of the number of exchanges performed on the network node. A second method includes capturing and saving arrival timestamps for each of a number of timing messages in a set of timing messages received from another network node. This second method also includes sending the timestamps to at least the another node in response to completion of the set of timing messages.

Description

technical field [0001] The present invention relates generally to networks and, more particularly, to measuring clock offsets of network nodes. Background technique [0002] It is widely believed that pure software solutions for clock synchronization suffer from unavoidable "system noise" (process dispatch, interrupt handling, etc.) that limits accuracy to 10 microseconds or more. When microsecond-level synchronization is required, hardware solutions are used, eg, network adapters with IEEE 1588 (Precision Time Protocol) support at both ends of the communication link. [0003] Such as figure 1 As depicted in , a typical software timestamp exchange has client node A send timestamp T1 to server node B, which receives timestamp T1 at time T2. Server node B then sends a reply at time T3, and client node A receives the reply at time T4. T1 and T4 are measured using client node A's clock; T2 and T3 are measured on server node B's clock. From this information the offset between...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/08
CPCH04L47/10H04J3/0682H04J3/0667H04J3/0638
Inventor S·弗罗利希M·H·T·哈克X·孟L·张
Owner INT BUSINESS MASCH CORP