Library Technology Guides

---

Volume 4 Number 10 (October 1984)

OSI and data communications

As highlighted by a number of recent articles in LSN, data communications are of increasing concern to libraries, particularly those wishing to use telecommunications to link remote terminals to a central computer and libraries seeking to interconnect remote systems for search and messaging access. A library administrator investigating data communications options will not venture far before encountering reference to the Open Systems Interconnect (OSI) Reference Model.

Until recently, data communication has lacked industry-wide standards, probably because computing has not been a regulated industry and communication among computer devices is a relatively recent development. All that purchasers have been able to expect is that all equipment supplied by a single vendor will be compatible with other equipment from that vendor. Because each computer vendor supports its own unique network structure, it has been impossible to interconnect systems supplied by different vendors. An overwhelming number of systems are able to communicate only with their genre. The development of standards to enable the linkage of equipment supplied by different vendors has appeal for both users and vendors. Users are not tied to a particular vendor, and because easier interconnection increases the use of distributed processing, vendors can access a larger market.

These perceived benefits fueled the development and approval, under the auspices of the International Standards Organization (ISO), of a network architecture model based on open systems interconnection as an international standard. The result if the OSI Reference Model (DIS 7496).

The first step in the development of OSI was to define all of the tasks required to permit two users to communicate across a network. The second step was to organize the tasks so that link functions were grouped together for most efficient interaction. The model is based on a layered architecture which segments the problem of systems linkage into functional groups or levels, each of which has unique attributes and --interacts with adjacent layers in the model. Each layer defines a discrete task: the layers build on each other to define operations of increasing complexity. The determination of the number of layers in the OSI model was influenced by a concern that they be sufficient to provide for the ready implementation of the structure, but not so many as to hinder development; and to minimize the number of interactions across layer boundaries. The resulting OSI model has seven layers, or levels and serves not only as a template for the design of network protocols, but has also become a powerful tool in analyzing and understanding network functions. The names and numbers of the levels of the model have become a part of the definition of communication products from long distances packet networks to local area networks.

OSI is not a specification of a particular network system design. Rather, the model is a framework, or skeleton, that permits standard interconnect procedures to be defined as protocols or rules which enable diverse users to interconnect and exchange information, regardless of their particular network or equipment vendor.

The model's only requirement is that- a system or device be connected to a physical communications medium through which access can be gained to one or more other systems. The medium can be as simple as a point-to-point communications line or as complex as interconnected private, local, and packet-switched networks. The device can be a computer, a terminal or anything else that has the intelligence necessary for information processing and communication. The interconnected systems may, but need not, be products of the same vendor.

In order of increasing complexity, the layers and their major functions are:

Physical layer

This is the lowest layer of the OSI architecture. It serves to permit the transfer of a bit stream over a physical circuit. The services defined by this level include acquiring, maintaining, and disconnecting the physical circuits that form the connecting path. Physical layer protocols handle the electrical and mechanical interfaces as well as the procedural requirements of the interconnection medium. These include connector type and voltage levels and the signaling procedures for control of the connection. The OSI model requires that the physical level be satisfactory for the transmission of "transparent data"; it cannot use procedures that restrict the characters that users can send across the connection. Typical physical layer protocols include the P8-2320, the P8-449 family, CCITT x.25 and X.21 facility interfaces, other CCITT V and X series recommendations, and media access protocols for local area networks.

Data link layer

Procedures in this level of the model are responsible for reliable delivery of link control data and user information over a point-to-point or multipoint link that has been established at the physical layer. Link layer protocols manage the establishment, control, and termination of error-free links; and control the flow of user data. Data link control protocols include the character-oriented binary synchronous communications (BSC) conventions, ANSI X3.28, DDCMP, and the more recent bit-oriented ADCCP and its international counterpart, HDLC.

Network layer

Procedures in the network layer select a route from among the available data links arranged as a network. This layer provides services for moving data through a network with concatenated data links and multiple routes available between points. These services include routing, switching, sequencing of data, flow control, and error recovery. Although some are duplicated at the link level, these functions are for network connections rather than data links.

Network layer protocols isolate the transport layer from concern for routing and switching. These protocols select and control logical paths and connections between networks user end points. Internet protocols, which control routing and recover between network nodes, and gateway protocols, which control data transfer between network, form the upper sublayers of this level of the model.

The CCITT X.25 packet layer is the most well-known network layer protocol.

Transport layer

This level of the model provides end-user-to-end-user assurance of information transfer; the user does not have to be concerned about the actual movement of the information. It is the highest layer directly associated with the movement of data through the network. This layer provides the higher layers, which represent the users of the communications service, with a universal transparent transfer mechanism. The transport layer is expected to optimize the use of available resources while meeting user requirements. It does this by segmenting or blocking messages that are not economical for network transmission.

Because transport protocols are responsible for ensuring the end-to-end integrity of the data exchange, they must bridge the gap between services provided by the underlying network and those required by the higher layers. Development work is still going on at this level. Simple transport layers will be used when a network provides a high-quality, reliable service; a complex transport protocol will be used when the underlying service is poor. In effect, the transport layer duplicates recovery mechanisms and other features that should have been provided by the lower layers.

Session layer

Services in this level coordinate the communications interchange between co-operating application processes. Sessions are established when one application process requests access to another. The session layer provides two categories of services: administrative and dialogue. An administrative service establishes and releases a connection between two presen-tation entities. After a session is established, dialogue services control and supervise the actual data exchange. Current session protocols include ECMA 75 and CCITT X.62, which is used in Teletex services.

Presentation layer

This level of the model serves to ensure compatible syntax among the communicating processes by adjusting data structures, formats, and codes. An application uses presentation layer services to properly interpret the information being transferred. It provides each user with an exchange dialog with the network (and therefore with other users); it is compatible with local operating and data format requirements. The services of this level include translation, formatting, etc. It also provides a means to request connections through the session layer and to terminate connections when communication is complete.

Work on formal presentation protocols has made significant progress; for example, recent work has aligned the many versions of videotex protocols into a single international presentation protocol.

Application layer

Services in this level of the model provide a window by which the user gains access to the communications services provided by the architecture. Since this is the highest layer of the OSI architecture, the application layer provides its services to the application process only. This layer is often identified as the "user," but it is more properly the user interface to the host computer's communication method. The application layer provides communication services directly to the user. These services include identifying the cooperating processes, authenticating the communicant, verifying authority, determining the availability of resources, and ensuring agreement on syntax. Applications do not reside in the layer; the layer is simply the means for the applications to gain access to the services provided by the communications architecture.

Work on the formal definition of application layer service descriptions and protocols will meet the needs of a specific applications such as libraries, banking, airlines, etc.

The OSI layers are also often described by their numerical position in the architecture. For example, the physical layer is Level 1, and the application layer is Level 7.

Previous communications systems have also been based on layered approaches. Computer manufacturers have offered layered network architectures to interconnect their own equipment lines. Two examples are IBM's System Network Architecture and Digital's DECnet. These architectures, however, are basically homogeneous because total compatibility occurs only within the computer product line of a single vendor. With the open systems architecture, the layered approached is used as a skeleton on which compatibility is built between heterogeneous or different computer systems.

EASYNET for easier data base searching

A new company has been formed to promote easier access to online data base searching by casual, untrained end users. Scheduled for introduction in mid-October, the EASYNET service is the first product from Telebase Systems, Inc., a Pennsylva-nia company which includes several former employees of the Institute for Scientific Information, a major producer of hardcopy and machine-readable abstracting and indexing tools. In addition to providing "user friendly" access to online data bases, the system guides the user through the search process, and also provides an innovative approach to the pricing of such searching.

To gain access to EASYNET, the user connects to the system by dialing an 800 telephone number (l-800-EASYNET). After being greeted by the system, the user is asked for a VISA or MasterCard credit card number. The system then verifies card, and if valid, permits the user to continue. The first menu screen asks the user to press one of the numbers 1 through 4 to find information about persons, places, subjects, or organizations. Each choice leads the user to another screen which refines the search further until the system can determine which vendor and data base are most appropriate to search. Once the determination is made, EASYNET then helps the user to formulate a search question (with Boolean operators, if desired) using the same type of menu screens as were used earlier in the pro-cedure. At this point, the system dials out of the EASYNET computer and con-nects to the vendor/data base that the user has chosen. The user is unaware that switching is taking place and sees only a continuous communication with the system. Once the data base is searched, the user is told how many articles were found, and can choose to see their titles or abstracts, print them, have the complete article deliv-ered (overnight or by regular mail), end the search, or begin a new search.

A broad range of information will be available including news, entertain-ment, business, science, medicine, social science, arts and humanities, and public services. As of late Septem-ber, access agreements had been nego-tiated with Dialog, BPS and .SDC, Questel and Pergamon Online, and News- net. Other files and vendors are being added as agreements are completed. Users will also have access to an on-line encyclopedia-the Academic Ameri-can Encyclopedia-which can be searched in place of a data base.

EASYNET claims several major advantages over other data base search services. It is extremely simple to access because public telephone lines are used rather than the private net-works, and credit cards are used rather than passwords. No registration is required; there is no need to keep track of network telephone numbers, which vary with geographical location; nor is it necessary to remember pass-words. The client is billed by the credit; card company in the usual fa-shion. Familiarity with online data bases is-said to be unnecessary be-cause the system selects from the many hundreds of data bases available the one or two most appropriate for the user. The user need not be familiar with search languages because EASYNET automatically translates the search question into the language required by the vendor whose data base is being searched, and EASYNET's simple series of menu screens requires no search language of its own.

The pricing is also innovative, with the basic cost of an EASYNET search being $10.00. This comprises a $5.00 charge for connecting to the EASYNET computer and a $5.00 charge for each external file accessed during a search. There are no other data base usage charges, although additional charges are levied for retrieving abstracts ($2.00 per abstract) and for ordering articles. Requests for the delivery of documents are passed through EASYNET to established document delivery vendors/services. The system displays all charges at the end of the search.

EASYNET is expected to relieve both academic and public library staff from the burden of doing searches for patrons, and will also facilitate chargebacks for searching. On campuses with remote terminals hardwired to the central university computer, searches can be partially or fully subsidized by the university.

Telebase Systems has plans for the development of further services, over and above the addition of more vendors and data bases-including factual files- to EASYNET. Phase II of the development calls for enhancement of the service to allow more informed users to direct the system to connect them to data bases or services of their own choosing, rather than using the system's automatic select capability.

Telebase Systems has been assisted in its development of EASYNET by receiving the sponsorship of the National Federation of Abstracting and Information Services (NFAIS), an organization which represents a number of major data base producers and vendors. The initial agreement provides NFAIS member organizations with the exclusive option of having their data bases accessible through EASYNET; it also limits such participation in EASYNET to the data base producers and vendors which are members of NFAIS.

[Contact: Telebase Systems, Inc., 134 North Narberth Avenue, Suite 6, Narberth, PA 19072, (215) 664-6168.]

DataPhase and Uninet announce Data Share

DataPhase Corporation, a turnkey vendor of automated library systems, and Uninet, a public data network similar to Telenet and Tymnet, have announced a joint venture agreement to develop a national network to link automated library systems and to facilitate access to library systems from terminals and personal micros in homes and offices.

The network will be based on the Open System Interconnection (OSI) Reference Model, the same standards model which underlies the development of the Linked Systems Project among the bibliographic utilities and the Library of Congress. The OSI Model, described elsewhere in this issue, was developed by the International Standards Organization and has already been widely adopted by manufacturers of hardware and developers of software. The Model envisions seven layers of linkages, from the lowest physical layer of interconnection to the highest layer which provides users of specific applications access to heterogeneous or incompatible systems.

Standards are generally available for the four lowest levels of the model, but are still under development for the higher levels. The best known of the existing standards are the layer one RS232C interface and the layer three X.25 standard for packet switching. The latter is fundamental to libraries searching of the remote data bases of BRS, Dialog, and SDC through Telenet and Tymnet.

Data Phase is writing software for the higher level layers for mounting on a Tandem minicomputer. Terminals and other computers will be able to access the network host through the Unmet communications network. Customers will gain access to the network by dialing a local number. Rather than paying for the length of time on the line, customers of the Data Share network will pay a flat rate per screen of information.

The first demonstration of Data Share was at the 103rd Annual American Library Association Conference in Dallas, where two Data Phase ALIS II and one ALIS III systems at widely scattered locations were alternately accessed. AXIS II and III are heterogeneous or incompatible systems because the former uses Data General hardware with MIIS/MUMPS and the latter uses Tandem hardware with COBOL.

Since the successful demonstration of the linkage among two heterogeneous or incompatible systems supplied by a single vendor, attention has shifted to the linking of systems from different vendors. At least one of the other major turnkey vendors has agreed to discuss possible interconnection through Data Share.

Academic libraries and computers in instruction

Librarians in academic institutions are becoming increasingly involved in the determination and implementation of strategies for the use of computers in instruction. For some libraries the involvement begins when plans for the implementation of an automated library library system alerts academic administrators to the possibility of providing computer access for students, others are impacted by demands for library support in the form of the provision and maintenance of microcomputer laboratories for student use. The following notes present a skeletal overview of the different strategy options for using computers in instruction that have been adopted by various institutions. The options are arranged in a hierarchy with the highest level of commitment first.

High Technology

Adoption of this strategy represents a major commitment to preparing students to use computers, with required use of computers--up to 500 hours a year-and access to all appropriate campus computing facilities through a local area network. File-transfer protocols are provided-whether purchased packages or locally developed-so that students and faculty can move information from campus computer systems to storage on their own micros. The teaching of computer skills permeates the entire curriculum and students are encouraged to use computers in library research, writing, and communication. Students may be required to purchase computers. This is an expensive strategy, costing as much as 10 percent of an institution's educational and general budget. Only some 20 institutions have made this commitment, primarily privately endowed universities and those which have technically oriented curricula.

Basic Core

This strategy involves teaching most students to use computers as a major tool, with up to 100 hours of hands-on use per year. Each student may be expected to take one or more basic courses, but extensive use of computers would depend on the student's curriculum. A student in engineering would get considerably more exposure than a student in the humanities. Course-related laboratories would be available, but students not enrolled in a course requiring computer resources would have only limited access--most probably only to machines in the library or learning center. Students would not be required to purchase computers, but the institution would seek to negotiate student discounts for one or more makes of micros. There would be no local area network, nor would the institution facilitate the transfer of files by purchasing or developing file transfer protocols.

Computer Literacy

Computer literacy programs aim at providing each student with up to 50 hours of hands-on use during his/her enrollment at the institution. At least one computer oriented course is required of each student. Students have access to microcomputer labs to meet course requirements.

Elective Option

Courses are offered to all students, but they are optional rather than required. Up to 50 percent of the students might take at least one course and they might have up to 20 hours of hands-on experience during their enrollment.

Keystrokes per hour continue to increase

Since 1980, there has been close to an 11 percent increase in keystrokes per hour, according to a recent statistical/ compensation survey conducted by the Data Entry Management Association, Stamford, CT. Twelve thousand keystrokes per hour is now a reasonable productivity rate for planning purposes.

More ADLIB and BLIS sales

Two of the smaller companies included in LSN's Local Systems Market Survey (Vol. IV Nos. 4 and 5) have announced new sales in recent months. Advanced Library Concepts' ADLIB system has been chosen by Gettysburg College; Southwest Christian College in Terrell, TX; and the Jefferson County (CO) Public School District. These libraries join the University of Hawaii as ADLIB users.

The University of Cincinnati has signed a software license for the Biblio-Techniques Library Information System (BLIS). This same system previously had been selected by Columbia University, University of California at San Diego, Indiana University, and the Toronto Metropolitan Public Library.

[Contact: Advanced Library Concepts, 9343 Tech Center Drive, Suite 175, Sacramento, CA 95826 (916) 364-0340. Biblio-Techniques, Inc., 828 East 7th Avenue, Olympia, WA 98501 (206) 786-1111.]

---

Maintained by Marshall Breeding

Copyright 1994-2024