Comparison Between Cluster Multicast Messaging and Unicast Messaging Mode

When servers are in a cluster, these member servers communicate with each other by sending heartbeats and indicating that they are alive. For this communication between the servers, either unicast or multicast messaging is used. This is chosen from the admin console in Cluster -> Configuration -> Messaging -> Messaging Mode.

To use multicast messaging, hardware configuration and support for multicast packets is required. Unicast does not have this requirement, which is why using unicast in latest versions is recommended.

When multicast messaging is used, it is a one-to-many communication, every server sends the notification/heartbeat/multicast packet to each other. This causes a heavy load on the application’s multicast buffer, so if the buffer is full, new multicast messages cannot be written to the buffer and the application is not notified when messages are dropped. So there is a possibility that the server instances miss the messages. This might lead in the cluster throwing out the server instances out of the cluster.

Unicast configuration is much easier because it does not require cross network configuration that multicast requires. Additionally, it reduces potential network errors that can occur from multicast address conflicts.

Mode of Communication:
Multicast – A multicast address and multicast port is used for listening to the messages.

Unicast – A network channel is used for communication between the servers. If no channel is specified, default network channel is used.

=====================

Method of communication between servers:
Multicast – Each server communicates with every member server in the cluster. Which means heartbeats are sent to every server.

Unicast – For the member servers in the cluster, group leaders are chosen and only those group leaders communicate with the servers among the group and these leaders notify each other about the availability of all the other servers.
For example : Suppose there are 6 servers in the cluster. 2 groups are made and there are 2 group leaders. Other 2 servers of the group will notify their leader that they are alive and the group leader will send this information to the leader of other group.

The frequency of communication in unicast mode is similar to the frequency of sending messages on multicast port.

=====================

For new server versions, using unicast is recommended because it is a simplified communication mode. But for backward compatibility with the previous versions, you will need to use multicast if there is a communication requirement between clusters of versions prior to WLS 10.0.

Whenever the messaging mode of the cluster is changed, all the servers in the cluster need a restart because the changes are not dynamic.

If you have any questions regarding unicast and multicast messaging mode, please let us know about it.

Best Regards,
Wonders Team!

Latest Comments

  1. pavan December 26, 2010
  2. kavita December 29, 2010
  3. Jetendra March 3, 2011
  4. Ashok March 11, 2011
    • divya March 11, 2011
  5. Ashok March 12, 2011
  6. Subash March 13, 2011
  7. Sridhar March 16, 2011
    • divya March 16, 2011
  8. suneel March 19, 2011
    • sadath January 22, 2014
  9. Nag March 21, 2011
  10. Administrator March 22, 2011
  11. Administrator March 22, 2011
  12. kiran March 30, 2011
  13. arzun May 3, 2011
    • divya May 18, 2011
  14. krishna May 27, 2011
  15. venkatsiva July 27, 2011
    • divya August 4, 2011
  16. venkatsiva September 4, 2011
    • divya September 20, 2011
  17. Mastan December 19, 2011
    • Divya February 23, 2012
  18. Dinesh April 12, 2012
    • Administrator May 9, 2012
  19. Tony June 7, 2012
    • Administrator June 9, 2012
  20. srinivas September 14, 2012
    • Administrator September 19, 2012
  21. Mohammed Azas November 25, 2014
  22. Mohammed Azas November 26, 2014
    • Administrator November 26, 2014
      • Mohammed Azas November 27, 2014
  23. kotesh bhupathi January 12, 2016
    • Divya February 11, 2016

Leave a Reply