Systems and methods for packet based timing offset determination using timing adjustment information

A method in a slave device to estimate an offset between the slave device and a master device, the method comprising:

• receiving a master→slave timing packet;
• obtaining timing adjustment information pertaining to at least part of a communications path between the slave device and the master device, at least some of the timing adjustment information obtained otherwise than from any received master→slave timing packet, transmit and receive times of the any received master→slave timing packet, and transmit and receive times of any transmitted slave→master timing packet;
• generating an estimate of the offset using the timing adjustment information and using the transmit and receive times for the master→slave timing packet;
• the method further comprising:
• transmitting and receiving timing packets on an ongoing first basis;
• and
• after a change in communications path to a different communications path, increasing a frequency of transmitting and receiving timing packets to speed up acquisition of delay characteristics for the different communications path.

A method in a slave device to estimate an offset between the slave device and a master device, the method comprising:

• receiving a master→slave timing packet;
• obtaining timing adjustment information pertaining to at least part of a communications path between the slave device and the master device, at least some of the timing adjustment information obtained otherwise than from any received master→slave timing packet, transmit and receive times of the any received master→slave timing packet, and transmit and receive times of any transmitted slave→master timing packet;
• generating an estimate of the offset using the timing adjustment information and using the transmit and receive times for the master→slave timing packet;
• the method further comprising generating an estimate of a fractional frequency offset using the timing adjustment information and using transmit and receive times for multiple master→slave timing packets, wherein said generating an estimate comprises:
• estimating a mean delay from the master device to the slave device using transmit and receive times for multiple master→slave timing packets and using the timing adjustment information;
• and
• generating an estimate of the fractional frequency offset using the mean delay.

A method in a slave device to estimate an offset between the slave device and a master device, the method comprising:

• receiving a master→slave timing packet;
• obtaining timing adjustment information pertaining to at least part of a communications path between the slave device and the master device, at least some of the timing adjustment information obtained otherwise than from any received master→slave timing packet, transmit and receive times of the any received master→slave timing packet, and transmit and receive times of any transmitted slave→master timing packet;
• generating an estimate of the offset using the timing adjustment information and using the transmit and receive times for the master→slave timing packet;
• wherein obtaining the timing adjustment information comprises at least one of:
• employing DCC (Data Communication Channel) in SONET/SDH to carry the information;
• employing GCC (General Communication Channel) in OTN to carry the information;
• employing management packets in Ethernet;
• and
• employing PTPv2 over UDP Signalling TLV (Type-Length-Value) in IP networks.

A network device comprising:

• a timing protocol module configured to transmit a slave→master timing packet and to receive a master→slave timing packet;
• the timing protocol module further configured to receive a topology update pertaining to at least part of a communications path over which the slave→master timing packet was transmitted and the master→slave timing packet was received indicating a change to the communications;
• a timing adjustment module further configured to perform at least one of:
• a) generate an estimate of a timing offset using the topology update and using transmit and receive times for the slave→master timing packet and the master→slave timing packet;
• and
• b) generate an estimate of a fractional frequency offset using the topology update and using transmit and receive times for multiple master→slave timing packets;
• wherein the network device is further configured to increase a speed of transmission of slave→master timing packets and receipt of a master→slave timing packets upon receipt of the topology update to increase a speed of acquisition of delay characteristics.

A method in a slave device to estimate an offset between the slave device and a master device, the method comprising:

• receiving a master→slave timing packet;
• obtaining timing adjustment information pertaining to at least part of a communications path between the slave device and the master device, at least some of the timing adjustment information obtained otherwise than from any received master→slave timing packet, transmit and receive times of the any received master→slave timing packet, and transmit and receive times of any transmitted slave→master timing packet;
• generating an estimate of the offset using the timing adjustment information and using the transmit and receive times for the master→slave timing packet;
• wherein the timing adjustment information is representative of a change in conditions in the network, and wherein the timing adjustment information representative of the change in conditions in the network is indicative of a change in topology.

A method in a slave device to estimate an offset between the slave device and a master device, the method comprising:

• receiving a master→slave timing packet;
• obtaining timing adjustment information pertaining to at least part of a communications path between the slave device and the master device, at least some of the timing adjustment information obtained otherwise than from any received master→slave timing packet, transmit and receive times of the any received master→slave timing packet, and transmit and receive times of any transmitted slave→master timing packet;
• generating an estimate of the offset using the timing adjustment information and using the transmit and receive times for the master→slave timing packet;
• wherein the timing adjustment information is representative of a change in conditions in the network, and wherein the offset is a timing offset, and wherein generating the estimate of the timing offset comprises:
• updating a mean master→slave delay based on the transmit and receive times for the master→slave timing packets and the timing adjustment information by applying a correction to the mean master→slave delay to account for the change in conditions in the network;
• updating a mean slave→master delay based on the transmit and receive times for the slave→master timing packets and the timing adjustment information by applying a correction to the mean master→slave delay to account for the change in conditions in the network;
• and
• determining the timing offset according to:
• timing offset=(mean master→slave delay mean+slave→master delay)/2;
• and
• wherein the timing adjustment information representative of the change in conditions in the network is indicative of a change in topology.

A method in a slave device to estimate an offset between the slave device and a master device, the method comprising:

• receiving a master→slave timing packet;
• obtaining timing adjustment information pertaining to at least part of a communications path between the slave device and the master device, at least some of the timing adjustment information obtained otherwise than from any received master→slave timing packet, transmit and receive times of the any received master→slave timing packet, and transmit and receive times of any transmitted slave→master timing packet;
• generating an estimate of the offset using the timing adjustment information and using the transmit and receive times for the master→slave timing packet;
• wherein the offset is a timing offset and wherein generating an estimate of the timing offset comprises:
• updating a mean master→slave delay based on the transmit and receive times for the master→slave timing packets and the timing adjustment information;
• updating a mean slave→master delay based on the transmit and receive times for slave→master timing packets and the timing adjustment information;
• and
• determining the timing offset according to:
• timing offset=(mean master→slave delay+mean slave→master delay)/2;
• and
• wherein at least one of:
• updating a mean master→slave delay based on the transmit and receive times for the master→slave timing packets and the timing adjustment information comprises employing a weighted averaging approach in which each master→slave delay is given a weight that is representative of the reliability of the accuracy of the delay;
• updating a mean slave→master delay based on the transmit and receive times for the slave→master timing packets and the timing adjustment information comprises employing a weighted averaging approach in which each slave→master delay is given a weight that is representative of the reliability of the accuracy of the delay.

A method in a slave device to estimate an offset between the slave device and a master device, the method comprising:

• receiving a master→slave timing packet;
• obtaining timing adjustment information pertaining to at least part of a communications path between the slave device and the master device, at least some of the timing adjustment information obtained otherwise than from any received master→slave timing packet, transmit and receive times of the any received master→slave timing packet, and transmit and receive times of any transmitted slave→master timing packet;
• generating an estimate of the offset using the timing adjustment information and using the transmit and receive times for the master→slave timing packet;
• wherein generating the estimate comprises determining a mean delay for timing packets based on the transmit and receive times for the timing packets, and the timing adjustment information comprises employing a weighted averaging approach in which each master→slave delay is given a weight that is representative of the reliability of the accuracy of the delay.