Interoperability is one of the top priority issues in the computer communication standardizations. The computer communication protocol design becomes complicated in order to cover both of the communication parts and content parts. The content parts need more flexibility for the future evolution. The author uses the underlying assumptions, architectural aspects and processing model aspects in order to identify the protocol design strategy with lessons learned in the past. The author describes existing extensibility frameworks. Then the author proposes a logical model for architectural design and processing model selection. This model gives a measure to verify the overall consistency for the evolution-tolerant protocol design. The author compares the fits among the logical model components and the possible interoperability strategies.