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• All peers hold predefined messages schemas (described with java classes).
• Messages follow schema in strict way - no fields are skipped and order of fields is guaranteed.
• Peers send messages as byte stream serializing fields one by one, no delimiters are used between fields and messages.
• For serializing POJO fields different techniques are used:
  • Message consumes already serialized byte array (e.g. JdkMarshaller for IgniteDiagnosticMessage, SchemaOperationStatusMessage... BinaryMarshaller for GridJobExecuteRequest#jobBytes).
  • User's BinaryObjects, Binarylizable are marshalled to byte array prior to serializing a message (the array is stored in cache structures).
  • Some messages contain POJO field annotated with GridDirectTransient, and additional byte array field fill with GridCacheMessage#prepareMarshal (e.g. BinaryMarshaller for GridChangeGlobalStateMessageResponse).
  • Some messages contains POJO that implements Message interface. 
• GridCacheMessage holds additional field depInfo. 

Discovery protocol

Current implementation of Discovery protocol:

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1. Message#writeTo, Message#readFrom logic is depends on a remote IgniteProductVersion.
2. Message#writeTo, Message#readFrom is auto-generated and stored separately from Message DTO classes.
3. Add Message#marshal(Marshaller), Message#unmarshal(Marshaller) methods - to marshal POJO fields if needed. 
4. Add @Since, @Until  annotations for Message classes and fields.
5. Marshalling must be done within Message#writeTo with specifying remote version to marshaller.
   1. byte[] fields in Message must be forbidden.

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