Intel® IXP400 Software

Access-Layer Components: Time Sync (IxTimeSyncAcc) API

Figure 95. IxTimeSyncAcc Component Dependencies

 

Client Application

 

 

(1588 Protocol)

 

Access-Layer Interface

 

 

 

IxTimeSyncAcc

IxFeatureCtrl

 

IxOSAL

 

Hardware Interface

 

 

 

IEEE 1588

 

Black Solid Arrow

- Client Invocation Path

Internal

Black Dotted Arrow

- Interrupt Invocation Path

 

Blue Dotted Arrow

- Interface with dependent components

External

 

 

B4392-01

20.2.1IEEE 1588 PTP Protocol Overview

As mentioned at the beginning of this chapter, the IEEE 1588 Precision Time Protocol (PTP) is used to synchronize independent clocks running in distributed network elements/nodes to a high degree of accuracy (in the nanosecond to sub-microsecond range). This section provides a very brief overview of the IEEE 1588 specification elements that relate to this IEEE 1588 hardware and software subsystem. For a more complete understanding of IEEE 1588, refer to IEEE Std 1588 - 2002, IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems, November 8, 2002 (available at http://ieee1588.nist.gov/).

The PTP protocol defines four timing-related messages: Sync, Delay_Req, Follow_Up and Delay_Resp. Furthermore, the protocol identifies a network element/node as either a master or a slave. The sequence and usage of the protocol messages vary depending on whether the node is configured in slave or master mode. Components within the PTP messages, such as the UUID and Sequence ID fields, are used by the master and slave elements/nodes to identify themselves and relate the sequence in which the PTP messages are exchanged.

Synchronization Sequence

The master provides the clock source to which all the slave nodes synchronize.

The master sends a Sync message to the slave node, carrying in it the master node’s system time as a timestamp. The master may also use Follow_Up message with the timestamp of the last Sync message to provide more accurate timestamp details to a slave, after accounting for the PHY,

April 2005

IXP400 Software Version 2.0

Programmer’s Guide

284

Document Number: 252539, Revision: 007

 

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Intel IXP400 manual Ieee 1588 PTP Protocol Overview, Access-Layer Components Time Sync IxTimeSyncAcc API