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Iroha2 development will continue after the initial version is published and several networks might be already live. When the new versions are ready, the networks will start upgrading the nodes, and therefore to not to disrupt the network at the time of an upgrade, nodes have to know the version in messages. Nodes might choose to support several older message formats, conditionally handling the logic.
Also client libraries need to be aware with what version of the API they are interacting, to properly report if they do not support this version, and conditionally handle versions that they do support.
Solution
JSON Based API
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