RFC relevance of services

As per Relevance of the word services, we have this rfc below:

Network Working Group C.
Request for Comments: 1240 Open Software
W.
Wang Laboratories, Inc
K.
Cabletron Systems, Inc
June 1991

OSI Connectionless Transport Services on top of
Version: 1

Status of this

This document describes a protocol for running OSI
service on UDP. This RFC specifies an IAB standards track
for the Internet community, and requests discussion and
for improvements. Please refer to the current edition of the "
Official Protocol Standards" for the standardization state and
of this protocol. Distribution of this memo is unlimited

1. Introduction and

The Internet community has a well-developed, mature set of
transport and network protocols, which are quite successful
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
top of the TCP and UDP over the past decade. These have helped
Internet services and protocols to become widely-spread de
standards. In the past few years, the ISO and CCITT have defined
well-architected set of upper layer standards which
connection-oriented and connectionless session, presentation,
application layer services and protocols. These OSI upper
standards offer valuable services to application developers (e.g.,
dialogue control, transfer syntax, peer authentication,
services, etc.) which are not currently offered by the TCP/
standards

As indicated in RFC 1006, it is desirable to offer the OSI
layer services directly in the Internet without disrupting
facilities. This permits a more graceful convergence and
strategy from IP-based networks to OSI-based networks in the future
Using the approach of RFC 1006, this memo specifies how to offer
connectionless transport service using the User Datagram
(UDP) [RFC768] of the TCP/IP suite

We will define a Transport Service Access Point (TSAP) which

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-
protocol on top of UDP. By this means, OSI TPDU's can be
across the Internet network, and OSI connectionless upper layers
operate fully without knowledge of the fact that they are running
top of UDP/IP. In essence, the OSI T-UNIT-DATA service will use
as its connectionless network service provider

2.

The primary motivation for the standard described in this memo is
facilitate the process of gaining experience with OSI
upper layers protocols, i.e., S-UNIT-DATA [ISO9548], P-UNIT-
[ISO9576] and A-UNIT-DATA [ISO10035], and connectionless
protocol T-UNIT-DATA [ISO8602].

Though many OSI standard applications such as X.400 and FTAM
connection-oriented, it is recognized in the OSI reference
[ISO7498/AD1] as well as in practice that the connectionless-
operations are appropriate for certain distributed
classes and environments. The following connectionless
classes were identified by ISO SC21/WG6 [ISOSC21/WG6 N184]:

- Request-Response
- Broadcast/
- Inward Data
- Migratory/Unreliable

Among them, the "request/response" client-server application class
the most prominent one, which is gaining popularity and importance
It is observed that the connection setup and tear-down
exchanges and complex connection-oriented protocol machines
unnecessary overheads for a simple request/response exchange
a client application and a server application, especially in
communications environments such as LAN and ISDN. The
connectionless upper layers are thought to be highly effective
efficient, both in time and space, for the distributed
classes mentioned above

The stability, maturity and wide availability of UDP/IP are ideal
providing solid connectionless transport services independent
actual implementations

3. The

The [ISO 8072/AD1] standard describes the OSI
transport services definition. The [ISO 8602] standard describes
OSI connectionless transport protocols. A defining characteristic

Shue, Haggerty & Dobbins [Page 2]

RFC 1240 OSI on top of UDP June 1991

transport connectionless-mode transmission is the independent
of each invocation of the connectionless transport service

The OSI transport service definition describes the services
by the TS-provider and the interfaces used to access those services
It also describes the services required. This memo focuses on
UDP [RFC 768] can be used to offer the required services and
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

Shue, Haggerty & Dobbins [Page 3]

RFC 1240 OSI on top of UDP June 1991

TS Transport Services (implies connectionless
service in this memo

TSAP Transport Service Access

TS-peer a process which implements the mapping of
protocols onto the UDP interface as described
this

TS-user a process using the services of a TS-

TS-provider the abstraction of the totality of those
which provide the overall service between the
TS-

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
transport provided that there is pre-arranged knowledge about
other (e.g., protocol version, formats, options, ... etc.),
there is no negotiation before data transfer. In the above
one TS-user passes a message to the TS-provider, and the peer TS-
receives the message from the TS-provider. The interactions
TS-user and TS-provider are described by connectionless
primitives

All aspects of [ISO 8072/AD1] are supported in this memo with
exception: QOS (Quality of Service) parameter, which is left
future study

The OSI standards do not specify the format of a TSAP selector
Neither does this memo. However, implementors should consult
GOSIP 1.0 specification [GOSIP88/FIPS146] for an interpretation
this parameter, wherein the TSAP selector consists of two octets
a value of (binary) 1 identifies the service interface between
transport layer and session layer

4. The

This RFC assumes that UDP [RFC768] offers the following
primitives

send datagram - datagram is sent to the IP address/

read datagram - datagram is read from

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
created. This is a local matter

This memo reserves the use of UDP port 102 for the use
applications which realize the CLTS over UDP. However as with
1006, other port values may be used by prior agreement (e.g.,
use of the OSI Directory).

This RFC describes how to use these services to emulate the
connectionless-mode network service primitives, which are required
[ISO8602]:

N-UNIT-DATA.REQUEST - A NS-user requests unit data to be

N-UNIT-DATA.INDICATION - A NS-user is notified that unit
can be read from the

The mapping between the UDP service primitives and the
primitives expected by the connectionless transport peer entity
quite straightforward

connectionless network service
------------------------------ ---

N-UNIT-DATA.REQUEST send

N-UNIT-DATA.INDICATION read

The parameter mapping is

connectionless network service
------------------------------ ---

Source address source IP address
calling TS-

Destination address destination IP address
called TS-

Quality of service (ignored

NS-user data UD TPDU constructed from T-UNIT-

When the T-UNIT-DATA.REQUEST primitive is issued, the TS-
constructs a UD TPDU and sends it as a single datagram to the
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
read from UDP, and a T-UNIT-DATA.INDICATION primitive is generated

5. Packet

The following is the UD TPDU structure which is encapsulated in
data field

1 2 3 m m+1
+--------------------------------------------------+
| LI | UD | Variable Part | User Data |
| | 01000000 | | |
+--------------------------------------------------+

LI (octet 1) - the length of the header including parameters,
excluding the LI and user data, with a
value of 254

UD (octet 2) - the type of

Variable Part (octets 3 to m) - the source and destination TSAP id'
Parameter code: source TSAP 11000001
destination TSAP 11000010
Parameter length: the length of the parameter, not
the parameter code or length fields, with
maximum value of 254
Parameter value: source or destination T-

The optional checksum parameter is not required in
variable part since the UDP checksum field in the UDP
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
service is 64,512 octets. This limit is further constrained by
lesser maximum datagram size supported by the two communicating
peers, which should be known by a priori agreement

6.

There is a general trend towards support of the OSI protocol suite
the Internet. This direction is being fostered by the
Activities Board (IAB) and its Internet Engineering Task Force,
by the Federal Networking Council. By offering an OSI
transport service on top of the Internet, this RFC will allow
applications to use the OSI connectionless upper-layer services
which are required to be conformant to the OSI upper

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,
A-UNIT-DATA have reached International Standard (IS).
applications based on OSI connectionless services become
available and OSI lower-layer service is widely implemented in
Internet, the underlying UDP/IP services can be simply replaced
the OSI lower layers

7.

Marshall T. Rose of PSI, Inc., provided many valuable comments
corrections

8.

[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 -
Processing Systems - OSI: Basic Reference
Addendum 1: Connectionless-mode Transmission",
May 1986.

[ISO8072] ISO, "International Standard 8072 - Information
Systems - OSI: Transport Service Definition", June 1984.

[ISO8072/AD1] ISO, "International Standard 8072 -
Processing Systems - OSI: Transport Service
Addendum 1: Connectionless-mode Transmission",
December 1986.

[ISO8602] ISO, "International Standard 8602 - Information
Systems - OSI: Connectionless Transport
Specification", December 1986.

[ISO9548] ISO, "International Standard 9548 - Information
Systems - OSI: Connectionless Session
Specification", April 1989.

[ISO9576] ISO, "Draft International Standard 9576 -
Processing Systems - OSI: Connectionless
Protocol Specification", April 1989.

[ISO10035] ISO, "Draft International Standard 10035 -
Processing Systems - OSI: Connectionless ACSE
Specification", April 1989.

[ISOSC21/WG6 N184] ISO SC21 WG6, "Justification for

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
the TCP - Version 3", RFC 1006, Northrop Research
Technology Center, May 1987.

Security

Security issues are not discussed in this memo

Authors'

Chikong
Open Software Foundation, Inc
11 Cambridge
Cambridge, MA 02142

Phone: (617) 621-8972
EMail: chi@osf.

William
Wang Laboratories, Inc
1 Industrial
Lowell, MA 01851

Phone: (508) 967-3403
EMail: bill@comm.wang.

Kurt
Cabletron, Inc
35 Industrial
Rochester, NH 03867

Phone: (603) 332-9400

Shue, Haggerty & Dobbins [Page 8]

if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.

RFC documents can be found at I.E.T.F.

Relevance System Copyright © 2002 Spectrum WorldResearch
other technical nosh by ServerMasters Corporation
collaboration of BobX