Wide Area Configuration

Wide area configuration is best suited for setups where the servers are spread across geographical locations. It is also suitable for setups which need fault tolerance.

Wide area configuration can be achieved by completing the following tasks:

  1. Planning the Setup.
  2. Configuring the Time Provider Group.
  3. Configuring the Time Consumers.


Planning the Setup

Create a plan for configuring the time provider group, which is a set of servers configured to ensure fault tolerance and optimal network usage.


Configuring the Time Provider Group

A time provider group consists of a set of servers that synchronize time in a fault tolerance setup and minimize network traffic.


Setting Fault Tolerance

  1. Configure at least two servers to communicate with each other in the peer-to-peer mode by adding a line similar to the following to each server's ntp.conf file:

    peer IP_address_of_peer 
  2. Configure the servers to contact their own unique external time sources in the client-server mode by adding a line similar to the following to each server's ntp.conf file:

    server IP_address_of_own_external_time_source 

    If one external time source link goes down, both time providers would not lose time synchronization.

  3. Configure the servers to fall back to their local clocks (self-synchronize) and ensure that the external time source gets preference over the local clock. To achieve this, use a lower preference for the local clock (stratum value of 3). Add lines similar to the following to each server's ntp.conf file:

    server 127.127.1.0
    fudge 127.127.1.0 stratum 3


Minimizing Network Traffic

To minimize network traffic, configure two servers, on either side of the network, in either the peer-to-peer mode or the client-server mode. These two servers can either have their own external sources or be self-synchronized.

For more information, see Peer-to-Peer Mode and Client-Server Mode.


Configuring the Time Consumers


Setting Fault Tolerance

To set fault tolerance, configure all the time consumers to have at least two time providers either in the client-server mode or the broadcast/multicast mode.

For more information, see Client-Server Mode and Broadcast and Multicast Mode.


Minimizing Network Traffic

To minimize network traffic, time consumers should not contact the time providers that are across costly WANs. Preferably, a time consumer should contact a time provider within its own local network.

You can use either manual configuration or auto configuration to configure a time consumer.

To use manual configuration, add lines similar to the following to each time consumer's ntp.conf file:

server IP_address_of_time_provider1_within_same_network
server IP_address_of_time_provider2_within_same_network 

or

To use auto configuration, add lines similar to the following to each time consumer's ntp.conf file:

broadcastclient subnet_broadcast_address

or

multicastclient


Sample Scenario

This sample scenario demonstrates how to configure a setup using wide area configuration.

Consider the scenario in the following figure.

Figure 10
Sample Scenario for Wide Area Configuration

In this scenario,

To configure the setup in this scenario using auto configuration:

  1. Configure Server1 to obtain time from the common time provider in the client-server mode and make this the preferred time provider by adding a line similar to the following to Server1's ntp.conf file:

    server IP_address_of_Common_Time_Provider prefer
  2. Configure Server1 to obtain time from its peer, Server2 in the peer mode.

    peer IP_address_of_Server2
  3. Configure Server1 to fall back to its own local clock. Set a low stratum value for the local clock so that preference is given to the external time sources. By setting a low stratum value, it will fall back to its local clock only when the other sources fail.

    server 127.127.1.0
    fudge 127.127.1.0 stratum 3
  4. Load XNTPD for the changes to take effect by entering the following at command prompt:

    Load XNTPD
  5. Repeat this procedure, with the appropriate changes to Server2's ntp.conf file, to configure Server2.

You are minimizing network traffic by configuring only Server1 and Server2 to obtain time from a time provider outside the local network.