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19.7.3. Fragmentation

This protocol fragments messages larger than certain size. Unfragments at the receiver's side. It works for both unicast and multicast messages. It is configured in the FRAG2 sub-element under the JGroups Config element. Here is an example configuration.

		<FRAG2 frag_size="60000" down_thread="false" up_thread="false"/>

The configurable attributes in the FRAG2 element are as follows.

  • frag_size specifies the max frag size in bytes. Messages larger than that are fragmented.


TCP protocol already provides fragmentation but a fragmentation JGroups protocol is still needed if FC is used. The reason for this is that if you send a message larger than FC.max_bytes, FC protocol would block. So, frag_size within FRAG2 needs to be set to always be less than FC.max_bytes.