Server time protocol messages and methods

• US 8,738,792 B2
• Filed: 11/15/2007
• Issued: 05/27/2014
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Carlson, Scott M., Crabtree, Donald, Dahlen, Dennis J., Dhondy, Noshir R., Sevigny, Denise M., Smith, Ronald M. Sr., Wierbowski, Judith A., Hack, Michael H.T.
• Primary Examiner(s): Nawaz, Asad
• Assistant Examiner(s): CHANG, STEPHANIE L
• Application Number:
  US11/940,518
• Publication Number:
  US 20080183899A1
• Time in Patent Office: 2,385 Days
• Field of Search: 709/230, 709/212, 709/239, 709/222, 709/223, 709/248, 370/352, 370/436, 370/475
• US Class Current: 709/230
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04L 43/0864 Round trip delays
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps
• CPC Class Codes: H04L 67/00 Network arrangements or protocols for supporting network services or applications user-to-user messaging H04L51/00; network arrangements, protocols or services for supporting real-time applications in data packet communications networks H04L65/00

Abstract

Server time protocol (STP) messages and methods of exchange thereof are provided for facilitating synchronization of processing units of a timing network. The STP messages include exchange time parameters (XTP) commands and responses, and STP control (STC) commands and responses. XTP message exchange processing includes: generating an XTP message command at a first processing unit including a command transmit timestamp field set by the first processing unit and a command receive timestamp field which is unset by the first processing unit; transmitting the XTP message command to a second processing unit; setting the command receive timestamp field in the XTP command with the time the XTP command is received at the second processing unit; and generating an XTP message response at the second processing unit, the message response including the command transmit timestamp set by the first processing unit and the command receive timestamp set by the second processing unit.

Claims

1. A method of exchanging messages for facilitating synchronization of processing units of a timing network, the method comprising:

receiving an exchange time parameters (XTP) message command at a second processing unit generated by a first processing unit, the XTP message command including a message command transmit timestamp field set by the first processing unit and a message command receive timestamp field unset by the first processing unit;

setting the message command receive timestamp field in the XTP message command with the time that the XTP message command is received at the second processing unit; and

generating at the second processing unit an XTP message response to be sent to the first processing unit, the XTP message response including the message command transmit timestamp set by the first processing unit and the message command receive timestamp set by the second processing unit obtained from the XTP message command;

wherein the XTP message command further comprises a message header dependent on a type of data link used to implement a server time protocol link between the first processing unit and the second processing unit, and a coordinated timing network (CTN) identifier of a timing network to which the first processing unit belongs;

wherein the XTP message command is transmitted to the second processing unit over the server time protocol link, and the message command transmit time stamp field is set by the first processing unit using a current time of day clock of the first processing unit, and is set immediately prior to transmitting of the XTP message command; and

wherein generating the XTP message response at the second processing unit comprises checking whether the CTN identifier received with the XTP message command matches a CTN identifier of a timing network to which the second processing unit belongs.

2. The method of claim 1, further comprising generating the XTP message command by the first processing unit, the generating including setting the message command transmit timestamp field at the first processing unit using a time of day clock of the first processing unit, and wherein setting the message-command-receive-timestamp field in the XTP message command by the second processing unit comprises setting the message command receive timestamp field in the XTP message command with the time that the XTP message command is received at the second processing unit using a time of day clock of the second processing unit.

3. The method of claim 1, wherein generating the XTP message response at the second processing unit further comprises including a message response transmit timestamp field set by the second processing unit and a message response receive timestamp field which is unset by the second processing unit.

4. The method of claim 3, further comprising transmitting the XTP message response from the second processing unit to the first processing unit, and setting the message response receive timestamp field in the XTP message response at the first processing unit with the time that the XTP message response is received at the first processing unit.

5. The method of claim 3, wherein the XTP message response to be sent to the first processing unit further comprises:

a message header dependent on a type of data link used to implement a server time protocol link between the first processing unit and the second processing unit across which the XTP message command and XTP message response are transmitted;

a response code indicative of the results of the attempt to execute the message command;

an XTP format, specifying the format of a format-dependent-area in the XTP message response;

a CTN parameter key indicating whether the contents of the format-dependent-area have changed;

a stratum set to the level of the second processing unit sending the XTP message response;

a timing mode set to the timing-mode of the second processing unit sending the XTP message response;

a timing state set to the timing state of the second processing unit sending the XTP message response;

a local clock server indication specifying whether the second processing unit sending the XTP message response is configured as a local-clock processing unit;

the CTN ID of the timing network to which the second processing unit sending the XTP message response belongs;

a current primary reference time (PRT) correction steering rate for the coordinated timing network;

a message interval set to the outgoing-message-interval field from timekeeping parameters set by the second processing unit;

a base steering rate set to the base-steering rate of the second processing unit sending the XTP message response;

a root delay set to a coordinated server time (CST)-round-trip delay at the second processing unit sending the XTP message response;

a root dispersion set to a CST-clock dispersion at the second processing unit sending the XTP message response;

a reference identifier set to a CST-reference ID at the second processing unit sending the XTP message response;

a reference timestamp set to a CST-reference timestamp at the second processing unit sending the XTP message response; and

an XTP format dependent data field set to one of multiple possible message response formats.

6. The method of claim 4, wherein the XTP message response further comprises an XTP format dependent data field set to one of multiple possible message response formats, the multiple possible message response formats comprising:

a first message response format used to deliver general CTN parameter information, the first message response format including an XTP general format, a primary reference time (PRT) correction steering block, a new CTN ID block, a leap second offset information block, and a total time offset;

a second message response format used to deliver a new stratum-1-configuration-information block, and if specified, a new CTN ID, the second message response format including an XTP general format, and a new stratum-1-configuration-information block; and

a third message response format used to deliver a time control parameter, the third message response format including an XTP general format and a time-control parameter information block.

7. The method of claim 4, further comprising processing the XTP message response at the first processing unit upon receipt thereof, the processing comprising:

adding the XTP message response to an XTP trace array and setting an entry code, wherein setting the entry code comprises;

setting the entry code to a first value to indicate invalid timestamp data if any timestamp contains all 0s or a timing state received from the second processing unit is the stopped state;

setting the entry code to a second value to indicate that timestamp data is valid, but should not be used to determine a usable clock source if a message-response timing state indicates unsynchronized, a message-response stratum of the second processing unit equals a maximum-stratum parameter, or a stratum level of the first processing unit is non-zero and the message-response stratum of the second processing unit is greater than the stratum level of the first processing unit; and

setting the entry code to a third value if neither the first or second value are set, the third value indicating that timestamp data is valid, and when the third value is set the method further comprises updating timekeeping-reference data associated with the second processing unit from information in the XTP message response, performing clock filtering-and-selection and updating; and

wherein when the first processing unit is in the synchronized state, checking data in a format dependent data field of a most recent valid time-keeping message response for updates, and if detected, using that data to update the first processing unit'"'"'s CTN parameters.

8. A computer program product for facilitating synchronization of processing units of a timing network, the computer program product comprising:

a non-transitory storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

receiving an exchange time parameters (XTP) message command at a second processing unit generated by a first processing unit, the XTP message command including a message command transmit timestamp field set by the first processing unit and a message command receive timestamp field unset by the first processing unit;

setting the message command receive timestamp field in the XTP message command with the time that the XTP message command is received at the second processing unit; and

generating at the second processing unit an XTP message response to be sent to the first processing unit, the XTP message response including the message command transmit timestamp set by the first processing unit and the message command receive timestamp set by the second processing unit obtained from the XTP message command;

wherein the XTP message command further comprises a message header dependent on a type of data link used to implement a server time protocol link between the first processing unit and the second processing unit, and a coordinated timing network (CTN) identifier of a timing network to which the first processing unit belongs;

wherein the XTP message command is transmitted to the second processing unit over the server time protocol link, and the message command transmit time stamp field is set by the first processing unit using a current time of day clock of the first processing unit, and is set immediately prior to transmitting of the XTP message command; and

wherein generating the XTP message response at the second processing unit comprises checking whether the CTN identifier received with the XTP message command matches a CTN identifier of a timing network to which the second processing unit belongs.

9. The computer program product of claim 8, further comprising generating the XTP message command by the first processing unit, the generating including setting the message command transmit timestamp field at the first processing unit using a time of day clock of the first processing unit, and wherein setting the message-command-receive-timestamp field in the XTP message command by the second processing unit comprises setting the message command receive timestamp field in the XTP message command with the time that the XTP message command is received at the second processing unit using a time of day clock of the second processing unit.

10. The computer program product of claim 8, wherein generating the XTP message response at the second processing unit further comprises including a message response transmit timestamp field set by the second processing unit and a message response receive timestamp field which is unset by the second processing unit.

11. The computer program product of claim 10, further comprising transmitting the XTP message response from the second processing unit to the first processing unit, and setting the message response receive timestamp field in the XTP Message response at the first processing unit with the time that the XTP message response is received at the first processing unit.

12. The computer program product of claim 10, wherein the XTP message response to be sent to the first processing unit further comprises:

a message header dependent on a type of data link used to implement a server time protocol link between the first processing unit and the second processing unit across which the XTP message command and XTP message response are transmitted;

a response code indicative of the results of the attempt to execute the message command;

an XTP format specifying the format of a format-dependent-area in the XTP message response;

a CTN parameter key indicating whether the contents of the format-dependent-area have changed;

a stratum set to the level of the second processing unit sending the XTP message response;

a timing mode set to the timing-mode of the second processing unit sending the XTP message response;

a timing state set to the timing state of the second processing unit sending the XTP message response;

a local clock server indication specifying whether the second processing unit sending the XTP message response is configured as a local-clock processing unit;

the CTN ID of the timing network to which the second processing unit sending the XTP message response belongs;

a current primary reference time (PRT) correction steering rate for the coordinated timing network;

a message interval set to the outgoing-message-interval field from timekeeping parameters set by the second processing unit;

a base steering rate set to the base-steering rate of the second processing unit sending the XTP message response;

a root delay set to a coordinated server time (CST)-round-trip delay at the second processing unit sending the XTP message response;

a root dispersion set to a CST-clock dispersion at the second processing unit sending the XTP message response;

a reference identifier set to a CST-reference ID at the second processing unit sending the XTP message response;

a reference timestamp set to a CST-reference timestamp at the second processing unit sending the XTP message response; and

an XTP format dependent data field set to one of multiple possible message response formats.

13. The computer program product of claim 11, wherein the XTP message response further comprises in XTP format dependent data field set to one of multiple possible message response formats, the multiple possible message response formats comprising:

a first message response format used to deliver general CTN parameter information, the first message response format including an XTP general format, a primary reference time (PRT) correction steering block, a new CTN ID block, a leap second offset information block, and a total time offset;

a second message response format used to deliver a new stratum-1-configuration-information block, and if specified, a new CTN ID, the second message response format including an XTP general format, and a new stratum-1 configuration information block; and

a third message response format used to deliver a time control parameter, the third message response format including an XTP general format and a time-control parameter information block.

14. The computer program product of claim 11, further comprising processing the XTP message response at the first processing unit upon receipt thereof, the processing comprising:

adding the XTP message response to an XTP trace array and setting an entry code, wherein setting the entry code comprises;

setting the entry code to a first value to indicate invalid timestamp data if any timestamp contains all 0s or a timing state received from the second processing unit is a stopped state;

setting the entry code to a second value to indicate that timestamp data is valid, but should not be used to determine a usable clock source if a message-response timing state indicates unsynchronized, a message-response stratum of the second processing unit equals a maximum stratum parameter, or a stratum level of the first processing unit is non-zero and the message-response stratum of the second processing unit is greater than the stratum level of the first processing unit; and

setting the entry code to a third value if neither the first or second value are set, the third value indicating that timestamp data is valid, and when the third value is set the method further comprises updating timekeeping-reference data associated with the second processing unit from information in the XTP message response, performing clock filtering-and-selection and clock updating; and

wherein when the first processing unit is in the synchronized state, checking data in a format dependent data field of a most recent valid time keeping message response for updates, and if detected, using that data to update the first processing unit'"'"'s CTN parameters.

15. A system to facilitate exchange of messages for synchronization of processing units of a timing network, the system comprising:

a memory; and

a processor in communications with the memory, wherein the computer system is configured to perform a method, the method comprising;

receiving an exchange time parameters (XTP) message command at a second processing unit of a coordinated timing network generated by a first processing unit thereof, the XTP message command including a message command transmit timestamp field set by the first processing unit and a message command receive timestamp field unset by the first processing unit;

setting the message command receive timestamp field in the XTP message command with the time that the XTP message command is received at the second processing unit;

generating at the second processing unit an XTP message response to be sent to the first processing unit, the XTP message response including the message command transmit timestamp set by the first processing unit and the message command receive timestamp set by the second processing unit obtained from the XTP message command;

wherein the XTP message command further comprises a message header dependent on a type of data link used to implement a server time protocol link between the first processing unit and the second processing unit, and a coordinated timing network (CTN) identifier of a timing network to which the first processing unit belongs;

wherein the XTP message command is transmitted to the second processing unit over the server time protocol link, and the message command transmit timestamp field is set by the first processing unit using a current time of day clock of the first processing unit, and is set immediately prior to transmitting of the XTP message command; and

wherein generating the XTP message response at the second processing unit comprises checking whether the CTN identifier received with the XTP message command matches a CTN identifier of a timing network to which the second processing unit belongs.

16. The system of claim 15, further comprising generating the XTP message command by the first processing unit, the generating including setting the message command transmit timestamp field at the first processing unit using a time of day clock of the first processing unit, and wherein setting the message-command-receive-timestamp field in the XTP message command by the second processing unit comprises setting the message command receive timestamp field in the XTP message command with the time that the XTP message command is received at the second processing unit using a time of day clock of the second processing unit.

17. The system of claim 15, wherein generating the XTP message response at the second processing unit further comprises the second processing unit including a message response transmit timestamp field set by the second processing unit and a message response receive timestamp field which is unset by the second processing unit, and further comprising the second processing unit transmitting the XTP message response from the second processing unit to the first processing unit, and setting the message response receive timestamp field in the XTP message response at the first processing unit with the time that the XTP message response is received at the first processing unit.