rfc: considering mandatory version-handshake

[joreg]

we're considering introducing a mandatory version-handshake as part of the protocol, after the connection was established. this is to enforce handling of versions on both ends (client/server). typically the connection will be closed if the client and server versions do not match.

but we can also see the special case, where the end with the higher version can decide if the connection will work or should be closed. this is because the end with the higher number may be backwards compatible.

proposed sequence of events:

• Connection established
• Client sends version-Info -> if server has lower or equal version, it sends back version-info -> else it sends an empty info, indicating a version mismatch and closes the connection
• Client receives valid version-info -> if client has can handle the servers version, it sends and Initialize -> else it closes the connection

e.g.: client-version: 0.0.1 server-version: 0.0.0

1. server is not capable of deciding, lets client decide
2. server sends version
3. client either closes the connection or sends initialize-command

client-version: 0.0.0 server-version: 0.0.1

1. server decides if it can handle that client
   • yes: server sends version info client sends initialize
   • no: server sends empty info to signal version missmatch and closes connection

[i-n-g-o]

after further considering there seems to be no benefit in specifying a mandatory version-handshake. a version-handshake is current implemented in the web-client and is considered good practice. other clients may do this differently.