Protocol Design

There are many possibilities and issues to be decided on when designing a protocol. Some of the issues include:

• Is it to be broadcast or point to point?
  Broadcast must be UDP, local multicast or the more experimental MBONE. Point to point could be either TCP or UDP.
• Is it to be stateful vs stateless?
  Is it reasonable for one side to maintain state about the other side? It is often simpler to do so, but what happens if something crashes?
• Is the transport protocol reliable or unreliable?
  Reliable is often slower, but then you don’t have to worry so much about lost messages.
• Are replies needed?
  If a reply is needed, how do you handle a lost reply? Timeouts may be used.
• What data format do you want?
  Two common possibilities are MIME or byte encoding.
• Is your communication bursty or steady stream?
  Ethernet and the Internet are best at bursty traffic. Steady stream is needed for video streams and particularly for voice. If required, how do you manage Quality of Service (QoS)?
• Are there multiple streams with synchronisation required?
  Does the data need to be synchronised with anything, e.g. video and voice?
• Are you building a standalone application or a library to be used by others?
  The standards of documentation required might vary.