Chapter 10: Version Management
10.1 Version Number Format
DTP uses semantic versioning with a major version number and a minor version number:
{ major: number, minor: number }
Every Logical_Frame's header includes a protocol version number field that identifies the protocol version used by that frame.
10.2 Version Compatibility Rules
DTP_Engine supports simultaneously processing Logical_Frame formats from both the current version and the previous major version.
| Received Frame Version | Handling |
|---|---|
| Current version | Normal processing |
| Previous major version | Compatible processing (backward compatible) |
| Higher version | Send version incompatibility notification |
| Lower version (beyond compatibility range) | Send version incompatibility notification |
10.3 Version Incompatibility Handling
When the receiver receives a Logical_Frame whose header protocol version number is higher than its supported version:
- Do not process the frame
- Send a version incompatibility notification (VERSION_INCOMPATIBLE, 7001) to the sender
- Include the receiver's highest supported version number in the notification
Upon receiving a version incompatibility notification, the sender can:
- Downgrade to the receiver's supported version and resend
- Or notify the upper-layer application of the version mismatch
10.4 Protocol Evolution Strategy
DTP's version management ensures backward compatibility as the protocol evolves:
- Minor version upgrade: Adds new fields or features without breaking the parsing of existing frame formats
- Major version upgrade: May change the frame format, but maintains compatibility with the previous major version
This means terminal devices and Fay do not need to upgrade simultaneously — as long as the version difference is within one major version, both parties can communicate normally.