Method for synchronizing local clocks in a distributed computer network

Abstract

The invention relates to a method for synchronizing local clocks in a distributed computer network, where the computer network consists of a number of end systems and at least two switches, where each end system is connected to at least two switches via bidirectional communication links, and where a configured subset of end systems and switches executes the method in form of a synchronization state machine, characterized in that a) the state machine uses at least three different frame types (coldstart frame type, coldstart acknowledge frame type, and integration frame type), and b) the states in the state machine are either the to belong to an unsynchronized set of states or belong to a synchronized set of states, and c) all end systems that are configured as Synchronization Master periodically send coldstart frames in one of the unsynchronized states, and d); all end systems that are configured as Synchronization Master react to the reception of a coldstart frame by sending a coldstart acknowledgment frame a configurable coldstart offset timeout after the reception of the coldstart frame on all replicated communication channels, provided that the end system is in a state in which the synchronization state machine defines a transition for coldstart frames, and where the coldstart offset timeout is reset when a consecutive coldstart frame is received before the coldstart acknowledge is sent, and e) all end systems that are configured as Synchronization Master react to the reception of a coldstart acknowledgment frame by starting a configurable coldstart answer offset timeout, provided that they are not already executing the coldstart offset timeout, and entering a synchronized state when the coldstart answer offset timeout expires.

Description

Background technique [0001] The present invention relates to synchronizing local clocks in a distributed computer network. Of particular interest to the present invention are computer networks that exchange information by sending the information over communication links between components in the network. Without limiting the specific implementation of the invention, we use standard Ethernet as an illustrative example. In standard Ethernet, end systems are connected via network switches via bidirectional communication links. An end system would communicate with a second end system or group of end systems by sending the information to the switch, which would then relay the information to the receiving end system or other end systems. Likewise, end systems can be directly connected to each other via bidirectional communication links, making the apparent distinction between end systems and switches indistinguishable in some configurations. Therefore, we generally use the term c...

AI Technical Summary

Problems solved by technology

[0002] The problem of clock synchronization is the problem of bringing the local clocks of different components into close agreement

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