Method for determining a propagation time of a telegram in a communication network, and corresponding network components

Network components for operation in a communications network, the network components comprising:

• a first network component having a local clock;
• a second network component having a local clock;
• a plurality of further network components to be synchronized with one another in time;
• a communications link;
• said first and second network components for a purpose of determining a propagation delay of a message along said communications link between said first network component and said second network component are configured to:
• send the message from said first network component to said second network component along said communications link, and to register a send time of the message and save a corresponding item of send-time information for the message;
• and
• use the send-time information to determine the propagation delay of the message along said communications link;
• said second network component is configured to return the message to said first network component immediately after the message arrives at said second network component, wherein said second network component receives the message and returns the message immediately after receipt to said first network component, solely at a physical, bit-transmission level;
• said first network component is configured to register, on receiving a returned message, a receive time for the message and to save a corresponding item of receive-time information for the message;
• said first network component is configured to use the send-time information for the message and the receive-time information for the message to determine the propagation delay of the message along said communications link, the propagation delay of the message along the communications link being determined by using the equation:
• T
• i
• ⁢
• ⁢
• _
• ⁢
• ⁢
• j
• =
• t
• i
• ⁢
• ⁢
• 2
• -
• t
• i
• ⁢
• ⁢
• 1
• 2
• Where Ti_j is the propagation delay of the message along the communications link between said first network component i and said second network component j;
• ti1 is the send-time information defining a time the message is sent from said first network component i;
• and
• ti2 is the receive-time information defining a time the message is received at said first network component i;
• and
• said network components are configured to use the propagation delay to synchronize a respective said local clock.

A method for synchronizing local clocks in a communications network, the communications network having several network components and each of the network components having a local clock and the local clock of one of the network components being a grandmaster clock to which the local clock of each of remaining ones of the network components being synchronized, the method comprises the steps of:

• transmitting, via a first network component, a message to a second network component along a communications link, wherein the first network component registers a send time for the message and saves a corresponding item of send-time information for the message, wherein the first network component synchronizing a time of sending the message with a timestamp clock used for internal time stamping, in order to send the message exactly at the time of arrival of a timestamp pulse of the timestamp clock;
• using the send-time information to determine a propagation delay of the message along the communications link;
• returning, via the second network component, the message to the first network component immediately after the message arrives at the second network component, wherein the second network component receives the message and returns the message immediately after receipt to the first network component, solely at a physical, bit-transmission level;
• registering a receive time for the message and saving a corresponding item of receive-time information for the message upon receiving a returned message in the first network component;
• using the send-time information for the message and the receive-time information for the message to determine the propagation delay of the message along the communications link, the propagation delay of the message along the communications link being determined by using the equation:
• T
• i
• ⁢
• ⁢
• _
• ⁢
• ⁢
• j
• =
• t
• i
• ⁢
• ⁢
• 2
• -
• t
• i
• ⁢
• ⁢
• 1
• 2
• Where Ti_j is the propagation delay of the message along the communications link between the first network component i and the second network component j;
• ti1 is the send-time information defining a time the message is sent from the first network component i;
• and
• ti2 is the receive-time information defining a time the message is received at the first network component i;
• and
• using the propagation delay to synchronize the local clocks of the network components to the grandmaster clock.