RFC 983 (rfc983) - Page 1 of 27

ISO transport arrives on top of the TCP

Network Working Group                                  D. E. Cass (NRTC)
Request for Comments: 983                              M. T. Rose (NRTC)
                                                              April 1986

                ISO Transport Services on Top of the TCP


Status of This Memo

   This memo describes a proposed protocol standard for the ARPA
   Internet community.  The intention is that hosts in the ARPA-Internet
   that choose to implement ISO TSAP services on top of the TCP be
   expected to adopt and implement this standard.  Suggestions for
   improvement are encouraged.  Distribution of this memo is unlimited.

1.  Introduction and Philosophy

   The ARPA Internet community has a well-developed, mature set of
   transport and internetwork protocols (TCP/IP), which are quite
   successful in offering network and transport services to end-users.
   The CCITT and the ISO have defined various session, presentation, and
   application recommendations which have been adopted by the
   international community and numerous vendors.  To the largest extent
   possible, it is desirable to offer these higher level services
   directly in the ARPA Internet, without disrupting existing
   facilities.  This permits users to develop expertise with ISO and
   CCITT applications which previously were not available in the ARPA
   Internet.  It also permits a more graceful transition strategy from
   TCP/IP-based networks to ISO-based networks in the medium- and
   long-term.

   There are two basic approaches which can be taken when "porting" an
   ISO or CCITT application to a TCP/IP environment.  One approach is to
   port each individual application separately, developing local
   protocols on top of the TCP.  Although this is useful in the
   short-term (since special-purpose interfaces to the TCP can be
   developed quickly), it lacks generality.

   A second approach is based on the observation that both the ARPA
   Internet protocol suite and the ISO protocol suite are both layered
   systems (though the former uses layering from a more pragmatic
   perspective).  A key aspect of the layering principle is that of
   layer-independence.  Although this section is redundant for most
   readers, a slight bit of background material is necessary to
   introduce this concept.

   Externally, a layer is defined by two definitions:

      a service-offered definition, which describes the services
      provided by the layer and the interfaces it provides to access
      those services; and,


Cass & Rose