RFC 1263 (rfc1263) - Page 2 of 19

TCP Extensions Considered Harmful

RFC 1263           TCP Extensions Considered Harmful        October 1991


2.  Creation vs. Extension vs. Evolution

2.1.  Protocol Creation

   Protocol creation involves the design, implementation,
   standardization, and distribution of an entirely new protocol. In
   this context, there are two basic reasons for creating a new
   protocol. The first is to replace an old protocol that is so outdated
   that it can no longer be effectively extended to perform its original
   function.  The second is to add a new protocol because users are
   making demands upon the original protocol that were not envisioned by
   the designer and cannot be efficiently handled in terms of the
   original protocol.  For example, TCP was designed as a reliable
   byte-stream protocol but is commonly used as both a reliable record-
   stream protocol and a reliable request-reply protocol due to the lack
   of such protocols in the Internet protocol suite.  The performance
   demands placed upon a byte-stream protocol in the new Internet
   environment makes it difficult to extend TCP to meet these new
   application demands.

   The advantage of creating a new protocol is the ability to start with
   a clean sheet of paper when attempting to solve a complex network
   problem.  The designer, free from the constraints of an existing
   protocol, can take maximum advantage of modern network research in
   the basic algorithms needed to solve the problem. Even more
   importantly, the implementor is free to steal from a large number of
   existing academic protocols that have been developed over the years.
   In some cases, if truly new functionality is desired, creating a new
   protocol is the only viable approach.

   The most obvious disadvantage of this approach is the high cost of
   standardizing and distributing an entirely new protocol.  Second,
   there is the issue of making the new protocol reliable. Since new
   protocols have not undergone years of network stress testing, they
   often contain bugs which require backward compatible fixes, and
   hence, the designer is back where he or she started.  A third
   disadvantage of introducing new protocols is that they generally have
   new interfaces which require significant effort on the part of the
   Internet community to use. This alone is often enough to kill a new
   protocol.

   Finally, there is a subtle problem introduced by the very freedom
   provided by this approach. Specifically, being able to introduce a
   new protocol often results in protocols that go far beyond the basic
   needs of the situation.  New protocols resemble Senate appropriations
   bills; they tend to accumulate many amendments that have nothing to
   do with the original problem. A good example of this phenomena is the
   attempt to standardize VMTP [1] as the Internet RPC protocol. While



O'Malley & Peterson