Major Description
The 1.7.7 specification explains the structure of framing but is ambiguous as to whether and how this applies to the handshake.
As the handshake request and responses are Avro values, they don't require framing per-se.
However, testing with the Java SaslSocketTransceiver has shown that, after SASL completion, a 4-byte header is sent by the client, which isn't specified in the handshake section of the specification, and the following n bytes includes the subsequent protocol-specific call.
If the handshake requests and responses are legitimately framed messages, then it seems there should be a terminating frame of 0 bytes between the handshake request and subsequent protocol request.