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OII Guide to Data Communications

The Open Information Interchange (OII) initiative is principally concerned with promoting the interchange of digital data using a global information infrastructure based on existing telecommunication networks. The OII initiative does not concern itself with how communications networks work, or whether the signals are carried by copper cable, fibre-optics, satellite links or some combination of these. What the OII initiative aims to do is to provide information about the wide range of standards that allow existing telecommunications networks to be used to provide services to end users.

Until recently there was a distinct difference between the sorts of systems developed for data transmission over general-purpose telecommunications networks and those developed specifically for computer-to-computer communications. Increasingly, however, the distinction between the Open System Interconnection (OSI) standards developed by member bodies of theInternational Standards Organization and theInternational Telecommunication Union (ITU) and theInternet computer-to-computer communications protocols developed by the Internet Engineering Task Force (IETF) have become blurred. As a result the two systems can, for most data interchange purposes, now be seen as component parts of the global information infrastructure.

Many different forms of digital communications have been standardized over the last century by the bodies that now form the ITU. Within Europe the backbone networks of most telecommunication systems are now digitally based. European telecommunications systems are rapidly being upgraded to implement theAsynchronous Transfer Mode (ATM) application of the Broadband ISDN (B-ISDN) specification. At the local level, however, digital communications are often not permitted. While some European countries, such as Germany, have widely adopted the Integrated Services Digital Network (ISDN) standard as the method for connecting offices and homes to local exchanges, in many countries any digital communications have to be routed as analogue signals sent over the twisted copper-wire pairs that form the backbone of existing analogue telephone systems. Before digital signals can be transmitted over such lines the digital signals need to converted into analogue form using a signal modulator/demodulator (modem).

Data compression techniques are increasingly being integrated with standards for the modulation of digital signals, so that the latest set of standards provide data transfer speeds of up to 56k bits per second, which very nearly matches the speed of a single 64k ISDN channel. ISDN signals can, however, be spread over up to 6 channels to provide broadband transmission services.

Note: The OII Standards and Specifications Listdoes not currently contain details of the many standards for telecommunications, data modulation or signal compression published by the ITU and its members. Details of the standards produced by these bodies can be obtained from the web server operated by ITU (http://www.itu.ch).

The OII Standards and Specifications List contains sections related to the following applications of digital data communications:

This guide provides supplementary information relating to:

About the Standards Development Organizations

Data communications standards are developed by a range of public organizations, including:

  • IETF -- Internet Engineering Task Force
  • ISO/IEC JTC1/SC6 -- JTC1 is the first (and only) Joint Technical Committee of ISO and IEC, and deals with Information Technology. SC6 is the subcommittee of JTC1 which deals with Telecommunications and Information Exchange between Systems.
  • ISO/IEC JTC1/SC32 -- SC32 is the subcommittee of JTC1 which deals with Data management and interchange.
  • ITU -- International Telecommunication Union (formerly CCITT: Comité Consultatif Internationale de Téléphones et Télégraphes).
  • ETSI -- The European Telecommunications Standards Institute has two sub-committees within the Terminal Equipment (TE) Technical Committee working on data transfer aspects of OSI communications:
    • TE3, the Message Handing Systems sub-committee
    • TE6, the Directory Systems sub-committee.

Many of these bodies operate as a single team, with standards developed by one organization being adopted or enhanced by another. In many cases joint meetings are held to ensure that the work of each organization is properly coordinated.

About OSI Application Standards

Open System Interconnection (OSI) data communication standards belong to the Application Layer (Layer 7) of the OSI Basic Reference Model (ISO 7498:1994). The Application Layer is specified in terms of "application contexts" and using building blocks called "application service elements" (ASEs). It resides above the Presentation Layer (Layer 6), which identifies alternative encodings, and the Session Layer (Layer 5), which provides dialogue control. Collectively, the three layers provide Application Services, and are commonly referred to as the Upper Layers.

Note: The Lower Layers of the OSI stack are Transport (Layer 4), Network (Layer 3), Link (Layer 2) and Physical (Layer 1).

There is today a great deal of discussion about the comparative advantages and disadvantages between the OSI standards and Internet protocols (see About the Internet below). Such discussions are beyond the scope of this document. However, it is important to note that there is no direct symmetry between the OSI application standards and the Internet application level protocols. Differences in their technical nature are closely related to the very different fundamental principles which underlie the OSI Reference Model and the Internet protocol suite, and the very different manners in which OSI standards and Internet protocols have been developed:

  • OSI application standards are based on an upper layer architecture and discrete modules. The three upper layer stacks provide full interworking flexibility (some would say at a cost of complexity). The OSI upper layers are in principle independent of the OSI Transport Layer and Network Layer.
  • Internet application protocols are written from the ground up. TCP/IP based application services such as FTP and TELNET are plugged directly into the Transport services.

It is in principle possible to run OSI application services over any lower layer stack, including over TCP/IP. At a more general level, any consideration about the relationship between OSI and TCP/IP needs to cover two distinct, albeit inter-related, aspects - the protocols for the upper layers on the one hand, and the transport and networking protocols on the other.

Deliberations over the co-existence and interoperability of OSI, TCP/IP and proprietary protocol suites in recent years have resulted in a number of specifications on multi-protocol operation, which aim to provide an "any-to-any" solution (any application service over any lower layer protocol stack). A good summary of these available specifications can be found in the EWOS Technical Guide ETG 053, Overview of approaches to multiprotocol coexistence and convergence in support of the Transport Service, copies of which are available from the EWOS Secretariat.

About the Internet

The Internet is a collection of networks, including the Arpanet, NSFnet, local networks at a number of university and research institutions, some military networks, and networks run by a wide range of commercial organisations. The term "Internet" applies to the entire web of networks.

Standards for the interchange of data over the Internet 'information superhighway' are developed by theInternet Engineering Task Force (IETF). Internal management of the IETF is handled by area directors. Together with the Chair of the IETF, they form the Internet Engineering Steering Group (IESG). The operational management of the Internet standards process is handled by the IESG under the auspices of the Internet Society. The Internet Architecture Board (IAB) is a body of the Internet Society responsible for overall architectural considerations in the Internet. It also serves to adjudicate disputes in the standards process.

There are two types of Internet documents: Internet-Drafts and Request for Comments (RFCs). Internet-Drafts have absolutely no formal status and can be changed or deleted at any time . The Secretariat maintains an Internet-Drafts index. RFCs are the official document series of the IAB, and are archived permanently (i.e. they are never deleted and, once an RFC is published, it will never change); however, it is important to note that not all RFCs are standards.

In many key areas the work of the IETF is directed through the World Wide Web Consortium (W3C). For details of their current working groups contacthttp://www.w3.org/.

Active IETF Working Groups

The following IETF working groups are currently developing new Internet standards (on-line users can click on the title of any group to obtain information on the current activity of that group):

Note: This list was generated from information supplied by IETF on 21st June 1999.

Applications Area
Area Director(s):
  • Keith Moore <moore@cs.utk.edu>
  • Patrik Faltstrom <paf@swip.net> Area Specific Web Page: Working Groups:
    General Area
    Area Director(s):
  • Fred Baker <fred@cisco.com> Working Groups:
    Internet Area
    Area Director(s):
  • Thomas Narten <narten@raleigh.ibm.com>
  • Erik Nordmark <nordmark@eng.sun.com>Working Groups:
    Operations and Management Area
    Area Director(s):
  • Randy Bush <randy@psg.com>
  • Bert Wijnen <wijnen@vnet.ibm.com> Area Specific Web Page: Working Groups:
    Routing Area
    Area Director(s):
  • David Oran <oran@cisco.com>
  • Rob Coltun <rcoltun@lightera.com> Working Groups:
    Security Area
    Area Director(s):
  • Jeffrey Schiller <jis@mit.edu>
  • Marcus Leech <mleech@nortel.ca> Area Specific Web Page: Working Groups:
    Transport Area
    Area Director(s):
  • Scott Bradner <sob@harvard.edu>
  • Vern Paxson <vern@aciri.org> Working Groups:
    User Services Area
    Area Director(s):
  • April Marine <april_marine@iengines.net> Area Specific Web Page: Working Groups:

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    This information set on OII standards is maintained by Martin Bryan of The SGML Centre and Man-Sze Li of IC Focus on behalf of European Commission DGXIII/E.

    File last updated: June 1999

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