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User clout fuels drive for open systems standards.


Starting this month, computer systems bought for use by the federal government will have to comply with a group of protocol standards known as the Government OSI Profile, or GOSIP.

It's the latest example of how users are taking the initiative in establishing standards for "open systems," or systems which are "open" to communicating and operating with systems from other vendors.

Such open systems will allow users throughout an organization to communicate freely with any other user, regardless of location or the type of computer they are using.

Users will also be able to access and share data and other information resources cooperatively to get a job done.

At the same time, vendors are responding to user demands for connectivity and interoperability by forming powerful alliances, often with users, to expedite the necessary hardware and software standards.

For interoperability, the key standards are based on the reference model for Open Systems Interconnection created by the International Standards Organization.

The OSI model describes information systems and devices in terms of seven functional layers.

The lower three layers represent the communications function--moving information from one system to another.

The middle layer is responsible for making sure the information is delivered from sending to receiving systems.

The upper three layers are processing-oriented.

Other important user considerations are software portability, where applications software written for one system can be used on all others> and a common user interface, which simplifies training and makes computers easier to use.


X/Open, a nonprofit consortium of international computer systems vendors, has taken the lead here.

Working with users, independent software vendors, and standards organizations, X/Open has specified a vendor-independent Common Applications Environment based on de facto and international standards.

More than 100 software companies worldwide are building compliant software products.

X/Open also has the support of two rival vendor alliances, Unix International and the Open Systems Foundation (OSF), who are seeking to position Unix as a standard operating system across all hardware platforms from micros to supercomputers.

Unix international promotes AT&T's Unix, while the OSF wants to keep the standard vendor-independent. Despite their differences, both have agreed to conform to X/Open's Common Applications Environment.

Recognizing the importance of user contributions, X/Open created a User Advisory Council in December 1987. Today, users often account for more than half the attendance at X/Open meetings.

According to Geoff Morris, X/Open's president and chief executive, the organization is positioning itself as "a conduit" from users to suppliers.

"The suppliers want it to happen," he says.

COS Leaves Its Mark

Perhaps the most powerful vendor-user alliance, however, is the non-profit Corporation for Open Systems (COS) whose members include the world's major computer suppliers, key government agencies from the U.S. and other leading industrialized nations, international communications carriers and service providers, and leading multinational corporations.

The Washington-based organization is chartered to speed the introduction of interoperable multi-vendor products and services operating under agreed-to OSI, ISDN, and related global standards.

COS grew out of a 1985 meeting of executives from 20 computer and communications companies. They concluded it was in the best interest of both vendors and users to move aggressively to make OSI standards a reality as quickly as possible.

That vision bore fruit last year when three products were awarded the COS Mark, signifying they had passed a battery of COS tests measuring their conformance to OSI standards for interoperability.

The idea of the COS Mark arose from concern that OSI products would not gain marketplace acceptance unless their conformance with the OSI standards could be established and their ability to interoperate with other products measured against the same conformance benchmark confirmed.

A related issue is that of harmonization, or agreement between OSI testing organizations worldwide on a single testing methodology and test platform.

Ian Davidson, COS vice president for engineering, believes that the move to harmonization must begin on a regional level.

COS and other major players in OSI testing in North America have already taken steps to establish mutual recognition and acceptance of each other's test methods.

Besides COS, the North American harmonization workshop includes the National Institute for Standards and Technology (NIST), the Canadian Standards Association, and the MAF/TOP Users Group.

In addition, COS has reached some key agreements with its European counterpart, SPAG (the Standards Promotion and Application Group), based in Belgium, and is actively engaged in dialogue with its counterparts in the Fast East, particularly the Promoting Conference for Open Systems Interconnection (POSI).

Based on progress so far, however, few are predicting a definitive harmonization accord between North American and Japanese test organizations in the near future.

Meanwhile, Britain's National Computing Centre has joined with British Telecom and its PTT counterparts in France, Italy, and Germany to establish the Open Systems Testing Consortium.

OSTC has set up test laboratories in Europe to ensure that OSI testing of computer communications equipment is consistent throughout the continent.

Products or services approved by the OSTC will be given a mark, similar to the COS program.

Suppliers will need to have their equipment tested only once, in one country, rather than have to get it tested in each individual country in which it could be used.

COS' performance testing program was able to benefit from some pioneering work done by NIST on interoperability.

NIST arranged for vendors of prototype OSI products to conduct interoperability tests between their products on a round-robin basis using a packet-switching network, OSInet, created for the purpose.

Among the lessons learned from OSInet was that OSI developers faced too many different implementation possibilities and alternatives due to the growing array of OSI specifications.

These had to be narrowed, and agreement reached on particular protocol combinations, or stacks, that would be implemented and tested.

The resulting stack specifications, called the OSI Implementors Workshop profiles, helped COS focus on creating the methods and produres for OSI conformance and product-interoperability testing.

Also, some stack profiles, known as Internationally Standardized Profiles, have been adopted as part of the SOI standards.

X.400 And X.500

In testing for seven-layer OSI products for its Mark award, COS began with a protocol stack based on the MHS/X.400 application-layer standard. COS tested MHS (Message Handling System) products over both local-and wide-area networks.

Once the lower-layer protocol testing was completed, it was easier for COS to begin testing products based on the File Transfer, Access, and Management (FTAM) application-layer standard. Vendors could simply replace the application-layer portion of their MHS products with FTAM to yield a whole new product line.

Other major application-layer protocols in the OSI repertoire include the Virtual Terminal Protocol (VTP), designed to enable a diversity of terminal types to access a common software application> and Transaction Protocol (TP), intended to serve real-time, relatively short-message transactions such as airline reservations and automated teller transactions.

Two other key application-layer protocols under development are the Directory/X.500 and Network Management.

Directory services would provide a standardized "Yellow Pages" type of service for information networks, allowing users to find any information resource in the world.

The goal of the network management protocol is to permit global OSI networks to be managed, diagnosed, and reconfigured from a central control site.

To speed delivery of network management products based on open standards, eight of the largest computer and communications companies created the OSI/Network Management Forum in July 1988.

Details of the forum's efforts will appear in the Datacomm Update on Network Management in the October issue of Communications News.

X.500 became a formally approved ISO and CCITT standard in 1988, but it left many important technical gaps, particularly in the area of directory information access and control.

While not crucial to the technical operation of the directory, these controls are important factors in making X.500 acceptable to users, who have traditionally been concerned about the security of electronic-mail systems.

To address user concerns, CCITT is working on an improved version of the standard, which should be approved in 1992.

One of the key elements of X.500 is the use of distributed directory databases, which reside as close as possible to the electronic-mail systems they serve and provide ready means for inter-communications.

X.500 treats the directory systems as local and regional database servers and defines three types of protocols to locate an electronic-mail address no matter where it is stored: broadcast mode, which directs electronic-mail address queries to servers on a network> referral mode, which uses general location information to determine the address> and chaining mode, which passes requests in a daisychain fashion among servers.

While X.500 and X.400 are most closely associated with electronic mail, analysts believe their use-and importance--will ultimately extend to many other forms of communications.

X.500 directories, for instance, could store address lists of phone numbers and facsimile machines.

In the future, subscribers might be able to call a single number for operator assistance to obtain the telephone or fax number of someone in another country or on another continent.

Also, a group of leading computer and communications vendors joined to make X.400 more universally valuable by developing standard application program interfaces (APIs) for X.400.

These APIs are entended to provide a set of operating-system-independent interfaces between electronic-mail systems and other applications and X.400 gateways or servers operating on LAN or other computer platforms.

"Our goal is to encourage the integration of LAN applications with wide-area services," notes Stuart Mathison, vice president of Telenet Communications Corp., which helped spearhead the effort to provide computer hardware and software developers with a de facto industry standard for interfacing application programs with the X.400 facilities.

"We hope to provide all users within an organization with peer-level access to each other, regardless of their operating platforms," he says.


With local-area networks, the main standards impetus has come from the Institute for Electrical and Electronic Engineers (IEEE) and its 802 committee. Once developed, the IEEE 802 standards are forwarded to the American National Standards Institute for approval as ANSI standards, and ultimately as ISO standards.

The overall IEEE 802 standards consist of a group of final and proposed specifications for LANs that deal with the physical and link layers of the OSI reference model.

The 802.1 specification describes the relationship between the other 802 standards and how they, in turn, relate to the OSI reference model.

802.3 specifies a CSMA/CD (Carrier Sense Multiple Access/Collision Detection) protocol based upon the Ethernet design promoted by Xerox, Intel, and Digital Equipment> 802.4 specifies a token-passing bus topology based upon the General Motors Manufacturing Automation Protocol (MAP)> 802.5 deals with the tokenpassing method using a ring topology based on IBM's Token Ring.

Unquestionably, these standards have helped fuel the explosion of LANs throughout both the public and private sectors.

Now, however, LAN users increasingly want to build larger networks and to interconnect their existing LANs.

To provide this type of high-speed operation and backbone connection in a campus or metropolitan environment, the IEEE is working on an 802.6 standard for metropolitan-area networks.

The IEEE will probably formally adopt the 802.6 standard by the end of the year, and forward it to the ISO for approval as ISO 8802-6.

In contrast to LANs, MANs need very high data rates (on the order of 100 Mb/s or higher), extended geographical coverage of several hundred miles, and a large number of stations ... theoretically any number but practically limited to about 1000.

Conventional LAN access schemes are inappropriate for MANs> CSMA/CD schemes result in idle time on the line because of collisions and backoffs, while token passing creates idle time on the medium because of the required circulation of the token.

These inefficiencies have little impact on the performance of a relatively small LAN, but the impact is magnified significantly by the MAN's larger geographical score.

For its topology, the 802.6 uses a dual bus design developed by Telecom Australia. Known as Distributed Queue Dual Bus (DQDB), the design uses two unidirectional buses supporting transmission in opposite directions.

Every station bus has two transmission links, allowing full-duplex communications between any pair of nodes.

A key feature of DQDB is that the buses operate independently of each other and of the access units, so that stations may fair or be removed from the network without causing operational problems elsewhere.

Also, the network can heal itself in the case of bus failure.

Transmissions on each bus are formatted in fixed-length entities called "slots."

Two access methods are used: the Queued Arbitrated access method supports services that are not time-sensitive, while the Pre-Arbitrated access method assigns specific octet positions within a transmission slot for use by different stations with time-sensitive applications.

As a public network, DQDB subnets can provide switching and routing for high-speed data, voice, and video applications, as well as the interconnection of private DQDB subnets and other private networks. Private DQDB networks can interconnect host computers, terminals, LANs, PBXs, and video conferencing services.

In many of its features, the 802.6 MAN resembles a precursor to the broadband ISDN. Independently, work is in progress to develop standardized methods of combining existing low-speed LANs with ISDN to provide intergrated voice /data/video networks. The IEEE 802.9 committee working on this standard has chosen a star topology, figuring that a shared bus would not provide an adequate response time.

Each workstation on an 802.9 network would be connected to an access unit in a wiring closet acting as a traffic cop. The access unit can transmit info to workstations in a packet channel for data networks or in circuit channels handling the 64-kb/s B and D channels of ISDN.

The committee is also working on ways to allocate a lot of bandwidth to the circuit channel so that applications such as video conferencing can be accommodated.

Meanwhile, ANSI has already approved a standard for high-speed LANs using fiber-optic links. The Fiber Distributed Data Interface (FDDI) standard calls for data transmission at 100 Mb/s over an optical-fiber token-ring network than can support 500 stations separated by distances of up to 2 kilometers, for a total network length of 100 km.

No special repeaters, amplifiers or other signal-conditioning equipment is needed, just commonly available multi-mode fiber and optoelectronic components.

Used as a fiber-optic backbone, FDDI provides a highspeed data highway for connecting groups of departmental LANs.

Another important LAN standard is a version of the IEEE 802.3 Ethernet LAN for use with unshielded twisted-pair (UTP) wiring.

With the 10BASE-T networking standard, users no longer have to rewire their building for Ethernet LANs.

Most buildings wired for telephones within the last 10 years can accommodate 10 Mb/s over Ethernet networks using the same UTP wiring.

Also, for new installations, or for wiring older buildings, UTP is inexpensive and easy to use and install.

In contrast to Ethernet, 10BASE-T uses a radial wiring approach in which wires to each user emanate out from a central hub in the wiring closet. The hub forms the connection to the network backbone. This wiring structure makes it easier to locate and isolate network problems.

Keeping Ring Open

Users and suppliers have taken different versions of Ethernet in stride, but the same is not true of token-ring networks.

When IBM announced a 16-Mb/s version of its token-ring network operating at four times the speed of the IEEE 802.5 token-ring standard, vendors and users cried foul.

Vendors feared they would not recover the money spent on developing their 4-Mb/s products> users worried their 4-Mb/s investments would become obsolete.

Concerned by IBM's dominance over the market, a group of vendors formed the Open Token Foundation with the primary goal of "making the token ring a truly open standard." Its purpose is to work with the IEEE to ensure that modifications to the existing standard enjoy the wide participation of vendors and users in the decision-making process. It also encourages continued development of improved token-ring products that both add value to the standard and provide new benefits to users.

Today, users have a strong voice in OTF, with representatives from such major companies as Shell Oil, Coca Cola, and American Airlines.

Another user organization influential in setting standards is the MAP/TOP Users Group, formed in September 1985 and now including representatives from most of the Fortune 500 companies.

MAP and TOP are related communications specifications based on the PSO sevenlayer model.

MAP, or Manufacturing Automation Protocol, specifies network protocols for factory floor communications. It resulted from a task force initiated by General Motors in 1980 to identify communications standards that would provide for multi-vendor data communications.

TOP, or Technical and Office Protocol, specifies network protocols for technical and office environments and resulted from development work at Boeing to address multi-vendor communications in technical and office areas.

Since Layers 2 through 6 of the MAP and TOP protocols are similar, the standards have been promoted in tandem. Following the rapid growth of the MAP/TOP Users Group, separate user groups were formed in major industrial areas worldwide, including Europe, Australia, Japan, and Canada.

The World Federation of Users Groups also coordinates global activities.

More recently, the Information Technology Requirements Council was formed as the parent body for North American MAP/TOP efforts at further developing MAP/TOP standards.

Even so, controversy continues over the physical and application layers.

MAP was based on the IEEE 802.4 and token bus architecture, while TOP specifies IEEE 802.3 and CSMA/CD at the physical layer.

However, Europeans, for instance, believe that an Ethernet-based MAP is required since they use Ethernet in 95% of their present installed base.

One compromise being discussed is to implement international standards profiles, where users could mix and match upper- and lower-level specifications depending on their needs. With this approach, both the IEEE 802.3 and 802.4 could be used successfully, depending on application requirements.
COPYRIGHT 1990 Nelson Publishing
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Author:Edwards, Morris
Publication:Communications News
Date:Aug 1, 1990
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