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This protocol is out of scope of this proposal.

Proposed changes

Cluster version

Validate joining node version

Server nodes stores ClusterVersion - set of Ignite versions in cluster (server and clients nodes). The joining node version must be checked versus the version (see actual Ignite versions in a cluster (within OnDiscoveryNodeValidationProcessor):

• If ClusterVersion a cluster contains nodes of only one version (all nodes are run same version), then the joining node can be greater/less than this version by up to 1 minor version.
• If ClusterVersion a cluster contains nodes of two versions, then joining node version must be one of the ClusterVersionthem.

Message DTO

There should be one serialization framework for communication and discovery protocol. 

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