From 4bfd864f10b68b71482b35c818559068ef8d5797 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 27 Nov 2024 20:54:24 +0100 Subject: doc: Add RFC documents --- doc/rfc/rfc1240.txt | 451 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 451 insertions(+) create mode 100644 doc/rfc/rfc1240.txt (limited to 'doc/rfc/rfc1240.txt') diff --git a/doc/rfc/rfc1240.txt b/doc/rfc/rfc1240.txt new file mode 100644 index 0000000..2add55a --- /dev/null +++ b/doc/rfc/rfc1240.txt @@ -0,0 +1,451 @@ + + + + + + +Network Working Group C. Shue +Request for Comments: 1240 Open Software Foundation + W. Haggerty + Wang Laboratories, Inc. + K. Dobbins + Cabletron Systems, Inc. + June 1991 + + + OSI Connectionless Transport Services on top of UDP + Version: 1 + +Status of this Memo + + This document describes a protocol for running OSI Connectionless + service on UDP. This RFC specifies an IAB standards track protocol + for the Internet community, and requests discussion and suggestions + for improvements. Please refer to the current edition of the "IAB + Official Protocol Standards" for the standardization state and status + of this protocol. Distribution of this memo is unlimited. + +1. Introduction and Philosophy + + The Internet community has a well-developed, mature set of layered + transport and network protocols, which are quite successful in + offering both connection-oriented (TCP) and connectionless (UDP) + transport services over connectionless network services (IP) to end- + users. Many popular network applications have been built directly on + top of the TCP and UDP over the past decade. These have helped the + Internet services and protocols to become widely-spread de facto + standards. In the past few years, the ISO and CCITT have defined a + well-architected set of upper layer standards which include + connection-oriented and connectionless session, presentation, and + application layer services and protocols. These OSI upper layer + standards offer valuable services to application developers (e.g., + dialogue control, transfer syntax, peer authentication, directory + services, etc.) which are not currently offered by the TCP/IP + standards. + + As indicated in RFC 1006, it is desirable to offer the OSI upper + layer services directly in the Internet without disrupting existing + facilities. This permits a more graceful convergence and transition + strategy from IP-based networks to OSI-based networks in the future. + Using the approach of RFC 1006, this memo specifies how to offer OSI + connectionless transport service using the User Datagram Protocol + (UDP) [RFC768] of the TCP/IP suite. + + We will define a Transport Service Access Point (TSAP) which appears + + + +Shue, Haggerty & Dobbins [Page 1] + +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 [Page 2] + +RFC 1240 OSI on top of UDP June 1991 + + + transport connectionless-mode transmission is the independent nature + of each invocation of the connectionless transport service. + + The OSI transport service definition describes the services offered + by the TS-provider and the interfaces used to access those services. + It also describes the services required. This memo focuses on how + UDP [RFC 768] can be used to offer the required services and provide + the interfaces. + + + The following is the model: + + + +-----------+ +-----------+ + | TS-user | | TS-user | + +-----------+ +-----------+ + | | + |CLTS interface | + |[ISO 8072/AD1] | + | | + _________________________________________________________________ + | | | | + | | | | + | +-----------+ UD TPDU +-----------+ | + | | TS-peer | <-----------------------> | TS-peer | | + | +-----------+ +-----------+ | + | | | | + | | | | + | | | | + | |UDP interface [RFC 768] | | + | | | | + | +-----------+ UDP datagram +-----------+ | + | | UDP | <-----------------------> | UDP | | + | +-----------+ (UD TPDU encapsulated) +-----------+ | + | | | | + | | | | + | | | | + | | | | + | | + | | + | TS-provider | + |_________________________________________________________________| + + +The following abbreviations are used: + + + CLTS Connectionless Transport + + + +Shue, Haggerty & Dobbins [Page 3] + +RFC 1240 OSI on top of UDP June 1991 + + + TS Transport Services (implies connectionless transport + service in this memo) + + TSAP Transport Service Access Point + + TS-peer a process which implements the mapping of CLTS + protocols onto the UDP interface as described by + this memo + + TS-user a process using the services of a TS-provider + + TS-provider the abstraction of the totality of those entities + which provide the overall service between the two + TS-users + + UD TPDU Unit Data TPDU (Transport Protocol Data Unit) + + Each TS-user gains access to the TS-provider at a TSAP. The two TS- + users can communicate with each other using a connectionless + transport provided that there is pre-arranged knowledge about each + other (e.g., protocol version, formats, options, ... etc.), since + there is no negotiation before data transfer. In the above diagram + one TS-user passes a message to the TS-provider, and the peer TS-user + receives the message from the TS-provider. The interactions between + TS-user and TS-provider are described by connectionless TS + primitives. + + All aspects of [ISO 8072/AD1] are supported in this memo with one + exception: QOS (Quality of Service) parameter, which is left for + future study. + + The OSI standards do not specify the format of a TSAP selector. + Neither does this memo. However, implementors should consult the + GOSIP 1.0 specification [GOSIP88/FIPS146] for an interpretation of + this parameter, wherein the TSAP selector consists of two octets and + a value of (binary) 1 identifies the service interface between OSI + transport layer and session layer. + +4. The Primitives + + This RFC assumes that UDP [RFC768] offers the following service + primitives: + + send datagram - datagram is sent to the IP address/destination + port + + read datagram - datagram is read from UDP + + + + +Shue, Haggerty & Dobbins [Page 4] + +RFC 1240 OSI on top of UDP June 1991 + + + Data can only be read from a receive port after the port has been + created. This is a local matter. + + This memo reserves the use of UDP port 102 for the use of + applications which realize the CLTS over UDP. However as with RFC + 1006, other port values may be used by prior agreement (e.g., through + use of the OSI Directory). + + This RFC describes how to use these services to emulate the following + connectionless-mode network service primitives, which are required by + [ISO8602]: + + N-UNIT-DATA.REQUEST - A NS-user requests unit data to be sent + + N-UNIT-DATA.INDICATION - A NS-user is notified that unit data + can be read from the NSAP + + The mapping between the UDP service primitives and the service + primitives expected by the connectionless transport peer entity are + quite straightforward: + + connectionless network service UDP + ------------------------------ --- + + N-UNIT-DATA.REQUEST send datagram + + N-UNIT-DATA.INDICATION read datagram + + +The parameter mapping is: + + connectionless network service UDP + ------------------------------ --- + + Source address source IP address from + calling TS-address + + Destination address destination IP address from + called TS-address + + Quality of service (ignored) + + NS-user data UD TPDU constructed from T-UNIT-DATA + + When the T-UNIT-DATA.REQUEST primitive is issued, the TS-peer + constructs a UD TPDU and sends it as a single datagram to the desired + IP address using UDP. + + + + +Shue, Haggerty & Dobbins [Page 5] + +RFC 1240 OSI on top of UDP June 1991 + + + When UDP indicates that a datagram has been received, a UD TPDU is + read from UDP, and a T-UNIT-DATA.INDICATION primitive is generated. + +5. Packet Format + + The following is the UD TPDU structure which is encapsulated in UDP + data field: + + 1 2 3 m m+1 n + +--------------------------------------------------+ + | LI | UD | Variable Part | User Data | + | | 01000000 | | | + +--------------------------------------------------+ + + LI (octet 1) - the length of the header including parameters, but + excluding the LI and user data, with a maximum + value of 254 + + UD (octet 2) - the type of TPDU + + Variable Part (octets 3 to m) - the source and destination TSAP id's + Parameter code: source TSAP 11000001 + destination TSAP 11000010 + Parameter length: the length of the parameter, not including + the parameter code or length fields, with a + maximum value of 254 + Parameter value: source or destination T-selector + + The optional checksum parameter is not required in the + variable part since the UDP checksum field in the UDP header + already performs the checking. + + User Data (octets m+1 to n) - all the data of the TSDU. + + The maximum NS-user data allowed in the OSI connectionless network + service is 64,512 octets. This limit is further constrained by the + lesser maximum datagram size supported by the two communicating UDP + peers, which should be known by a priori agreement. + +6. Conclusion + + There is a general trend towards support of the OSI protocol suite in + the Internet. This direction is being fostered by the Internet + Activities Board (IAB) and its Internet Engineering Task Force, and + by the Federal Networking Council. By offering an OSI connectionless + transport service on top of the Internet, this RFC will allow future + applications to use the OSI connectionless upper-layer services, + which are required to be conformant to the OSI upper layer + + + +Shue, Haggerty & Dobbins [Page 6] + +RFC 1240 OSI on top of UDP June 1991 + + + architecture. Currently, T-UNIT-DATA, S-UNIT-DATA, P-UNIT-DATA, and + A-UNIT-DATA have reached International Standard (IS). As + applications based on OSI connectionless services become widely + available and OSI lower-layer service is widely implemented in the + Internet, the underlying UDP/IP services can be simply replaced with + the OSI lower layers. + +7. Acknowledgements + + Marshall T. Rose of PSI, Inc., provided many valuable comments and + corrections. + +8. References + + [GOSIP88] U.S. Department of Commerce/National Bureau of Standards, + [FIPS146] "Government Open Systems Interconnection Profile (GOSIP)", + August 1988. + + [ISO7498/AD1] ISO, "International Standard 7498 - Information + Processing Systems - OSI: Basic Reference Model + Addendum 1: Connectionless-mode Transmission", + May 1986. + + [ISO8072] ISO, "International Standard 8072 - Information Processing + Systems - OSI: Transport Service Definition", June 1984. + + [ISO8072/AD1] ISO, "International Standard 8072 - Information + Processing Systems - OSI: Transport Service Definition + Addendum 1: Connectionless-mode Transmission", + December 1986. + + [ISO8602] ISO, "International Standard 8602 - Information Processing + Systems - OSI: Connectionless Transport Protocol + Specification", December 1986. + + [ISO9548] ISO, "International Standard 9548 - Information Processing + Systems - OSI: Connectionless Session Protocol + Specification", April 1989. + + [ISO9576] ISO, "Draft International Standard 9576 - Information + Processing Systems - OSI: Connectionless Presentation + Protocol Specification", April 1989. + + [ISO10035] ISO, "Draft International Standard 10035 - Information + Processing Systems - OSI: Connectionless ACSE Protocol + Specification", April 1989. + + [ISOSC21/WG6 N184] ISO SC21 WG6, "Justification for Connectionless + + + +Shue, Haggerty & Dobbins [Page 7] + +RFC 1240 OSI on top of UDP June 1991 + + + Services in the Upper Layers", June 1986. + + [RFC768] Postel, J., "User Datagram Protocol", RFC 768, + USC/Information Sciences Institute, September 1981. + + [RFC791] Postel, J., "Internet Protocol", RFC 791, + USC/Information Sciences Institute, September 1981. + + [RFC1006] Rose, M., and D. Cass, "ISO Transport Service on top of + the TCP - Version 3", RFC 1006, Northrop Research and + Technology Center, May 1987. + +Security Considerations + + Security issues are not discussed in this memo. + +Authors' Addresses + + + Chikong Shue + Open Software Foundation, Inc. + 11 Cambridge Center + Cambridge, MA 02142 + + Phone: (617) 621-8972 + EMail: chi@osf.org + + + William Haggerty + Wang Laboratories, Inc. + 1 Industrial Ave + Lowell, MA 01851 + + Phone: (508) 967-3403 + EMail: bill@comm.wang.com + + + Kurt Dobbins + Cabletron, Inc. + 35 Industrial Way + Rochester, NH 03867 + + Phone: (603) 332-9400 + + + + + + + + +Shue, Haggerty & Dobbins [Page 8] + \ No newline at end of file -- cgit v1.2.3