Communication over ethernet mac layer without TCP/IP part 1

I use two different o.s. at a embedded system. Altohough, there are so many solutations such as broadcast, IP sockets, non-reliable IP-less protocol and so on, but they can not meet our requerments.

Here are my concept:
A protocol must base on ethernet layer II and has capability to do TCP-friendly stuff. The requerments are below:

• Can set or get system parameter between A and B.
• This protocol must be extendable from dual systems to multiple systems.
• It can not fix at client and server mode. These two (or more) system can be client and server at the same time.
• We can transfer large file or multipart request/response over a transaction. And the upper layer applications do not have to worry about fragmentations.
• This protocol must provide Event/Notify. A could register events which is occurred at B. After registation, B must send notify while some events happened.
  

Here are issues:

1. How to define session and transations?
2. How to encoding payload ?
3. How to implement re-transmit ?
4. others