Clock Synchronization Protocol

Introduction If desired, you may operate the C4 CMTS on local clock without synchro-

nizing it to a network. If you choose to synchronize the C4 CMTS to a network time server, you must choose either Time of Day (TOD) or Network Time Protocol (NTP) as your synchronization protocol. If you intend to enable PacketCable, you must use NTP.

Procedure 7-1 How to Configure a Time of Day (TOD) Clock Protocol

The TOD server provides the time of day to cable modems and other customer premises equipment (CPE) devices connected to the Cadant C4 CMTS cable interfaces. The cable modem uses the ToD server to get the current date and time to accurately time-stamp its Simple Network Management Protocol (SNMP) messages and error log entries.

1 Configure the TOD server IP address and protocol for Transmission Control

Protocol (TCP) or User Datagram Protocol (UDP) commands:

configure tod server <ip address of server> {tcp|udp} 2 Configure the C4 CMTS to use the TOD time synchronization protocol:

configure clock network tod

3 Confirm the current clock network protocol as well as the local time using

the following command:

7

Procedure 7-2 How to Choose Network Time Protocol (NTP) for C4 CMTS

The purpose of this procedure is to configure the C4 CMTS as an NTP client. This means that the C4 CMTS clock is synchronized to the NTP server.

NOTE

PacketCable requires the use of NTP for network synchronization. Use step 1 if the NTP client is unicast; otherwise, go to step 2.

1 Configure the NTP client:

configure ntp server <ip address> [burst] [prefer] [minpoll <4-11>] [maxpoll <4-11>] [version <3 |4>]

Where 4-11 are exponents of 2. In other words, the possible values are 24, 25, 26 … 211, which equal 16, 32, 64 … 2048. The C4 CMTS becomes an NTP unicast client of the remote server at ip- address. The remote server distributes time synchronization to the C4 CMTS, but does not synchronize itself to the C4 CMTS. This is the most common NTP configuration for the C4 CMTS.

The optional burst parameter forces the C4 CMTS to send a sequence of time sync messages over a short period at each poll interval. This reduces the amount of time the C4 CMTS needs to synchronize its local clock. The optional prefer parameter designates the association with this server as the preferred time sync source unless the server is unreachable. The optional minpoll, maxpoll, and version parameters can be used to override the default parameters set by the config ntp minpoll | maxpoll | version commands on a per server basis if necessary.

2 Use one of the following commands to configure the C4 CMTS as an NTP

client listening to a broadcast or multicast server, or if is to be part of an NTP manycast group:

configure ntp server <ip-address> broadcast configure ntp server <ip-address> multicast configure ntp server <ip-address> manycast 3 Set the NTP re-synchronization timer:

configure ntp minpoll <4..11> configure ntp maxpoll <4..11>

Where 4-11 are exponents of 2. In other words, the possible values are 24, 25, 26 … 211, which equal 16, 32, 64 … 2048. These commands are used to set the default values for NTP minpoll,

maxpoll, and version parameters that will be assumed by subsequent configure ntp server | peer commands. Default for minpoll is 6, maxpoll is 10, and version is 4.

PacketCable requires that the maximum interval between consecutive attempts to synchronize the C4 CMTS local time of day clock must not exceed one hour. Therefore, NTP.MAXPOLL must not exceed 11 (that is 211 or 2048 seconds, which equals approximately 34 minutes). The CLI command configure ntp maxpoll <4 … 11>has a default value of 10. Also, the new CLI command configure ntp minpoll <4 … 11> sets the default minimum polling interval in the same way, where minpoll is strictly less than or equal to maxpoll.

4 Configure the time zone:

When no parameter is given (or invalid input is detected), this command enters interactive mode. In interactive mode, a list of available canonical time zone (TZ) names is displayed based on a given country name or ISO- 3166 country code. The local TZ name may then be selected by line number from the displayed list of TZ names for that country. In the example given below the time zones for the USA are requested.

C4 clock timezone

Enter country name or 2 letter code: US

1. US +404251-0740023 America/New_York Eastern Time

2. US +421953-0830245 America/Detroit Eastern Time - Michigan - most locations 3. US +381515-0854534 America/Louisville Eastern Time - Kentucky - Louisville area 4. US +364947-0845057 America/Kentucky/Monticello Eastern Time - Kentucky - Wayne County 5. US +394606-0860929 America/Indianapolis Eastern Standard Time - Indiana - most locations 6. US +382232-0862041 America/Indiana/Marengo Eastern Standard Time - Indiana - Crawford County 7. US +411745-0863730 America/Indiana/Knox Eastern Standard Time - Indiana - Starke County 8. US +384452-0850402 America/Indiana/Vevay Eastern Standard Time - Indiana - Switzerland County 9. US +415100-0873900 America/Chicago Central Time

10. US +450628-0873651 America/Menominee Central Time - Michigan - Wisconsin border

11. US +470659-1011757 America/North_Dakota/Center Central Time - North Dakota - Oliver County 12. US +394421-1045903 America/Denver Mountain Time

13. US +433649-1161209 America/Boise Mountain Time - south Idaho & east Oregon 14. US +364708-1084111 America/Shiprock Mountain Time - Navajo

15. US +332654-1120424 America/Phoenix Mountain Standard Time - Arizona 16. US +340308-1181434 America/Los_Angeles Pacific Time

17. US +611305-1495401 America/Anchorage Alaska Time

18. US +581807-1342511 America/Juneau Alaska Time - Alaska panhandle 19. US +593249-1394338 America/Yakutat Alaska Time - Alaska panhandle neck 20. US +643004-1652423 America/Nome Alaska Time - west Alaska

21. US +515248-1763929 America/Adak Aleutian Islands 22. US +211825-1575130 Pacific/Honolulu Hawaii

7

Chicago is selected.

By requesting CLI help on the command you can see that you can also configure the time offset using Greenwich Mean Time:

configure clock timezone ?

WORD country name/zone location e.g. America/Chicago, or GMT offset e.g. GMT-6 <cr> Use the following command to set the time zone offset in hours (and minutes, if applicable) from Greenwich:

configure clock timezone GMT[+|-hh[:mm]]

Use the no form of the command to disable the time zone setting:

configure clock [no] timezone

Use the following command to display the clock configurations and the time:

show clock detail

2004 August 4 09:53:39 CDT (DST) Network time sync protocol is TOD

TOD Server IP Address: 10.50.28.3 connection type: tcp These commands select the local TZ and DST rules based on canonical <TZ name> or GMT offset. The TZ and DST adjustments are made auto- matically whenever the local time is displayed or logged (see show clock detail or show log history command).

When a canonical <TZ name> is given, the built-in local TZ and Daylight Saving Time (DST) rules for that time zone location name are activated. This includes automatic adjustment of local time for TZ & DST and setting of the time zone abbreviation according to the rules. Examples of canonical TZ names are Europe/Paris, America/Chicago, or Asia/Hong_Kong. When a GMT offset is given, the local TZ is set accordingly, but no DST adjustments are made when local time is displayed or logged.

5 Configure the C4 CMTS to use NTP network synchronization: configure clock network ntp

6 Confirm the NTP configuration:

show ntp <associations |defaults>

Where: associations displays the status of NTP associations defaults displays default settings for NTP minpool, maxpool, and version

For example:

show NTP defaults

minpoll=6 maxpoll=10 ver=4

End of procedure

Show Clock Commands Use the following commands to view NTP status:

show clock

show clock detail show clock GMT show ntp

These commands display the local date and time in one-second resolution when the TOD client is active and in 1 millisecond resolution when the NTP client is active.

The output of show clock detail also shows the TZ abbreviation and the current DST/STD time status.

If you wish to see the time expressed as Greenwich Mean Time, use show clock GMT.

Manually Adjusting the C4

CMTS Internal Clock If there is an active network time protocol, you must first disable it before adjusting the clock on the C4 CMTS.

1 Use the following command to disable network synchronization: config clock no network

2 Manually set the C4 CMTS internal clock:

8. Host Names, User IDs, and