SERVER TIME PROTOCOL MESSAGES AND METHODS

• US 20080183899A1
• Filed: 11/15/2007
• Published: 07/31/2008
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: SMITH, Ronald M., WIERBOWSKI, Judith A., CRABTREE, Donald, CARLSON, Scott M., DAHLEN, Dennis J., DHONDY, Noshir R., HACK, Michel H.T., SEVIGNY, Denise M.
• Granted Patent: US 8,738,792 B2
• Time in Patent Office: Days
• US Class Current: 709/248
• 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 servers of a timing network, the method comprising:

generating an exchange time parameters (XTP) message command at a first server, the XTP message command including a message command transmit timestamp field set by the first server and a message command receive timestamp field which is not set by the first server;

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

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 server; and

generating an XTP message response at the second server, the XTP message response including the message command transmit timestamp set by the first server and the message command receive timestamp set by the second server obtained from the XTP message command.

2. The method of claim 1, wherein the XTP message command further comprises a message header dependent on a type of data link used to implement the server time protocol path between the first server and the second server, and a coordinated timing network (CTN) identifier of the first server.

3. The method of claim 1, wherein generating the XTP message command by the first server includes setting the message command transmit timestamp field at the first server using a time of day clock of the first server, and wherein setting the message-command-receive-timestamp field in the XTP message command by the second server 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 server using a time of day clock of the second server.

4. The method of claim 1, wherein generating the XTP message response at the second server further comprises including a message response transmit timestamp field set by the second server and a message response receive timestamp field which is not set by the second server.

5. The method of claim 4, further comprising transmitting the XTP message response from the second server to the first server over the server time protocol path, and setting the message response receive timestamp field in the XTP message response at the first server with the time that the XTP message response is received at the first server, wherein the message response transmit timestamp field is set by the second server using a current time of day clock of the second server, and is set immediately prior to transmitting the XTP message response to the first server over the server time protocol path, and wherein the method further comprises employing at the first server the message command transmit timestamp, message command receive timestamp, message response transmit timestamp and message response receive timestamp in determining a new time-of-day (TOD) clock for a coordinated timing network (CTN) comprising the first server and the second server.

6. The method of claim 5, wherein the XTP message response further comprises:

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 timing mode set to the timing-mode of the second server sending the XTP message response;

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

a CTN ID of the second server sending the XTP message response;

a current PRT correction steering rate for the coordinated timing network;

a base steering rate set to the base-steering rate of the second server sending the XTP message response; and

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

7. The method of claim 5, 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 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.

8. The method of claim 5, further comprising processing the XTP message response at the first server 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 server 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 server equals a maximum-stratum parameter, or a stratum level of the first server is non-zero and the message-response stratum of the second server is greater than the stratum level of the first server; 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 server from information in the XTP message response, performing clock filtering-and-selection and updating; and

wherein when the first server 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 server'"'"'s CTN parameters.

9. An article of manufacture comprising:

at least one computer usable medium having computer readable program code logic to facilitate synchronization of servers of a timing network, the computer readable program code logic when executing performing the following;

generating an exchange time parameters (XTP) message command at a first server, the XTP message command including a message command transmit timestamp field set by the first server and a message command receive timestamp field which is not set by the first server;

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

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 server; and

generating an XTP message response at the second server, the XTP message response including the message command transmit timestamp set by the first server and the message command receive timestamp set by the second server obtained from the XTP message command.

10. The article of manufacture of claim 9, wherein the XTP message command further comprises a message header dependent on a type of data link used to implement the server time protocol path between the first server and the second server, and a coordinated timing network (CTN) identifier of the first server.

11. The article of manufacture of claim 9, wherein generating the XTP message command by the first server includes setting the message command transmit timestamp field at the first server using a time of day clock of the first server, and wherein setting the message-command-receive-timestamp field in the XTP message command by the second server 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 server using a time of day clock of the second server.

12. The article of manufacture of claim 9, wherein generating the XTP message response at the second server further comprises including a message response transmit timestamp field set by the second server and a message response receive timestamp field which is not set by the second server.

13. The article of manufacture of claim 12, further comprising transmitting the XTP message response from the second server to the first server over the server time protocol path, and setting the message response receive timestamp field in the XTP message response at the first server with the time that the XTP message response is received at the first server, wherein the message response transmit timestamp field is set by the second server using a current time of day clock of the server unit, and is set immediately prior to transmitting the XTP message response to the first server over the server time protocol path, and wherein the computer-readable program code logic when executing further comprises employing at the first server the message command transmit timestamp, message command receive timestamp, message response, transmit timestamp, and message response receive timestamp in determining a new time-of-day (TOD) clock for a coordinated timing network (CTN) comprising the first server and the second server.

14. The article of manufacture of claim 13, wherein the XTP message response further comprises:

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 timing mode set to the timing-mode of the second server sending the XTP message response;

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

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

a CTN ID of the second server sending the XTP message response;

a current PRT correction steering rate for the coordinated timing network;

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

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

15. The article of manufacture of claim 13, 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 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.

16. The article of manufacture of claim 13, further comprising processing the XTP message response at the first server 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 server 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 server equals a maximum stratum parameter, or a stratum level of the first server is non-zero and the message-response stratum of the second server is greater than the stratum level of the first server; 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 server from information in the XTP message response, performing clock filtering-and-selection and clock updating; and

wherein when the first server 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 servers CTN parameters.

17. A system to facilitate exchange of messages for synchronization of servers of a timing network, the system comprising:

a first server of a coordinated timing network to generate an exchange time parameters (XTP) message command, the XTP message command including a message command transmit timestamp field set by the first server and a message command receive timestamp field which is not set by the first server;

the first server to transmit the XTP message command to a second server over a server time protocol path, wherein the message command transmit timestamp field is set by the first server using a time of day clock of the first server;

a second server of the coordinated timing network to receive the XTP message command and set the message command receive timestamp field in the XTP message command; and

the second server to generate an XTP message response, the XTP message response including the message command transmit timestamp set by the first server and the message command receive timestamp set by the second server obtained from the XTP message command.

18. The system of claim 17, wherein the XTP message command further comprises a message header dependent on a type of data link used to implement a server time protocol path between the first server and the second server, and a coordinated timing network (CTN) identifier of the first server.

19. The system of claim 17, wherein generating the XTP message command by the first server includes setting the message command transmit timestamp field at the first server using a time of day clock of the first server, and wherein setting the message-command-receive-timestamp field in the XTP message command by the second server 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 server using a time of day clock of the second server.

20. The system of claim 17, wherein generating the XTP message response at the second server further comprises the second server including a message response transmit timestamp field set by the second server and a message response receive timestamp field which is not set by the second server, and further comprising the second server transmitting the XTP message response from the second server to the first server over the server time protocol path, and setting the message response receive timestamp field in the XTP message response at the first server with the time that the XTP message response is received at the first server, wherein the message response transmit timestamp field is set by the second server using a current time of day clock of the second server, and is set immediately prior to transmitting the XTP message response to the first server over the server time protocol path, and wherein the method further comprises employing at the first server the message command transmit timestamp, message command receiver timestamp, message response transmit timestamp and message response receive timestamp in determining a new time-of-day (TOD) clock for a coordinated timing network (CTN) comprising the first server and the second server.