RFC 1240 (rfc1240) - Page 2 of 8
OSI connectionless transport services on top of UDP: Version 1
Alternative Format: Original Text Document
RFC 1240 OSI on top of UDP June 1991
to be identical to the services and interfaces defined in ISO 8072
and its Addendum 1, but we will in fact implement the ISO T-UNIT-DATA
protocol on top of UDP. By this means, OSI TPDU's can be delivered
across the Internet network, and OSI connectionless upper layers can
operate fully without knowledge of the fact that they are running on
top of UDP/IP. In essence, the OSI T-UNIT-DATA service will use UDP
as its connectionless network service provider.
2. Motivation
The primary motivation for the standard described in this memo is to
facilitate the process of gaining experience with OSI connectionless
upper layers protocols, i.e., S-UNIT-DATA [ISO9548], P-UNIT-DATA
[ISO9576] and A-UNIT-DATA [ISO10035], and connectionless transport
protocol T-UNIT-DATA [ISO8602].
Though many OSI standard applications such as X.400 and FTAM are
connection-oriented, it is recognized in the OSI reference model
[ISO7498/AD1] as well as in practice that the connectionless-mode
operations are appropriate for certain distributed application
classes and environments. The following connectionless application
classes were identified by ISO SC21/WG6 [ISOSC21/WG6 N184]:
- Request-Response Applications
- Broadcast/Multicast
- Inward Data Collection
- Migratory/Unreliable Processes
Among them, the "request/response" client-server application class is
the most prominent one, which is gaining popularity and importance.
It is observed that the connection setup and tear-down protocol
exchanges and complex connection-oriented protocol machines become
unnecessary overheads for a simple request/response exchange between
a client application and a server application, especially in reliable
communications environments such as LAN and ISDN. The OSI
connectionless upper layers are thought to be highly effective and
efficient, both in time and space, for the distributed application
classes mentioned above.
The stability, maturity and wide availability of UDP/IP are ideal for
providing solid connectionless transport services independent of
actual implementations.
3. The Model
The [ISO 8072/AD1] standard describes the OSI connectionless
transport services definition. The [ISO 8602] standard describes the
OSI connectionless transport protocols. A defining characteristic of
Shue, Haggerty & Dobbins