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Standards Chart Direction of Local-Area Network Advances.

Standards are starting to bring some semblance of order to loca-area network (LAN) offerings, though communications managers must still wrestle with a multiplicity of standards rather than a single one. Xerox has been successfl in establishing its Ethernet local-area network as one of the industry's de facto standards. More than 250 companies are now making Ethernet products, and Xerox claims an installed base of more than 20,000 Ethernet networks, many of them installed by vendors other than Xerox. Further, more than 30 Xerox products and a wide range of devices from other vendors, including Digital minicomputers, the IBM PC and other personal computers, can now be connected via Ethernet to form integrated office systems.

Ethernet was also the basis for one of the standards developed by the IEEE 802 committee on LAN standards. Like Ethernet, the IEEE Stnadard 802.3 specifies the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) media access method as a means by which two or more stations share a common bus transmission medium. The standard encompasses several media types and techniques for signal rates from 1 to 20 Mb/s, but it provides the necessary specifications and related paramter values for a 10-Mb/s baseband implementation identical to Ethernet. Initial differences between Ethernet and IEEE 802.3 have since been resolved by Xerox, making slight modifications to its original Ethernet design.

Likewise, IBM has been a driving force behind the development of the IEE 802.5 standard, which covers a token-passing ring architecture. One potential obstacle to this approach comes in the form of a Swedish engineer named Olof Soderblom, the holder of a patent he claims is basic to token-ring designs. Solderblom threatens to sue any vendor who sells a token-ring system without paying him a substantial sum for a license to use the patent, plus a royalty for each workstation in a network. IBM has already paid Soderblom more than $5 million for unlimited worldwide license to use his patent and his products, so it is unaffected by the controversy. Meanwhile, the IEEE committee has also developed the IEEE Standard 802.4 for a bus LAN using the token-passing access method.

One of the more-exciting standards efforts currently under way involves a broadband token-bus aproach to communications within factories using a coaxial cable backbone LAN. Spearheaded by General Motors, the so-called Manufacturing Automation Protocol covers the seven layers of the ISO model and incorporates communications standards developed by the IEEE, the National Bureau of Standards, the American National Standards Institute and the Internatonal Standards Organization. MAP already has the support of major computer vendors, including IBM, Digital Equipment, Data General and Hewlett-Packard, many of whom were involved in a multi-vendor demonstration of the network at the National Computer Conference.

For the backbone of the MAP network demonstration, General Motors selected the Token/Net token-passing broadband LAN from Concord Data Systems of Waltham, Massachusetts. Concord DAta was the first LAN manufacturer to endorse and market an IEEE 802.4-compatible LAN and, in conjunction with Gould AMI Semiconductors, has developed a custom chip set offering an advanced very large scale integration (VLSI) implementation of the MAP physical and data-link layers. The three-chip set is designed to be compatible with virtually every computer system on the market, according to the firm. In July, it introduced network software to reduce the costs of connecting MAP-compatible devices to the 802.4 token-bus LAN. The Token/Net software, in conjunction with the interface module, implements the physical and data-link layers of the MAP specification for host-to-host communications and provides an HDLC interface to higher layers of MAP software implemented in each host.

In June, Interactive Systems/3M introduced a local-area network that reportedly conforms to the IEEE 802.4 and MAP standards, and also meets the specifications of the IEEE 802.3 baseband standard. Called LAN/II, the network operates over a single coaxial cable and supports multiple-rate synchronous and asynchronous links between computers, workstations, industrial equipment, laboratory facilities and remote networks. The LAN/II physical network consists of a tree structure, with CATV-style taps, splitters, drop cables to individual nodes and two-way signal amplifiers where required. It operates at 10 Mb/s using a token-passing protocol, with network intelligence distributed among multiport Network Interface Units, which serve individual user devices and eliminate the throughput bottleneck of a head-end computer.

The 802.3 baseband version uses CSMA/CD access and Ethernet-type cable for office applications. Bridges and gateway variations for LAN/II include baseband-to-broadband, baseband-to-baseband and broadband-to-broadband links. A Network Management Unit collects and analyzes statistical data on network traffic and can configure the interface units to work with either ISO or DOD-based protocols, conduct remote system diagnostics and provide electronic mail service. The Ann Arobr, Michigan firm recently reached an agrement with Hewlett-Packard to cooperate in the development and marketing of broadband LANs and computer systems.

Despite these standareds efforts, LANs have yet to be fully integrated with major network architectures. LANs will continue to thrive as a terminal or PC interconnect vehicle, in the opinion of Stuart Wecker, president of Technology Concepts of Sudbury, Massachusetts. However, host-to-host operations will have to await the development of high-speed interconnect products to go on the computer bus and the appropriate software. Network Systems' Hyperchannel provides such a high-speed connection, but it is solely for large machines, Wecker said. He addressed the problem in part with a softwaree package called Etherway which, when used with the appropriate controller from Interlan of Chlmsford, Massachusetts (now a part of Micom Systems), links Ehternet with Digital's network architecture. Etherway creates a fully connected DECnet network among the nodes directly attached to Ethernet. Communication among these nodes is simplified since messages have to transverse only the Ethernet link, in contrast to the routing via intermediatee nodes that takes place in conventional networks. Technology Concepts has supplemented Etherway with two similar gateways for ring and broadband networks, called Ringway and Broadway, respectively. More recently, the firm has developed a more-comrehensive software package called Commu-Unity, which creates a packet-oriented networking structure to unify the diversity of computer hardwaree, operating systems and applications in current use.

Wecker also sees security as another "hole" in today's LAN product offerings. Datapro Research of Delran, New Jersey, also believes that data security is the biggest disadvantage of a LAN. By design, most LANs are easy to tap, the firm notes in a recent publication on local-area networks. Ease of tapping makes the network easy to expand and reconfigure, but also makes it vritually impossible to secure from simple physical intrusion, the report states. Some vendors have begun to address the security problem by implementing data encryption as an add-on feature, but encryption can only prevent the interception of data, according to the report. A relatively unsophisticated vandal reportedly can still jam or destroy data with ease. For this reason, users should never allow plant security applications, for example, to share the same cable plant as everyday data applications.

Separate networks should be set up for secure and open facilities, and if necessary, such nets can be interconnected to a secured bridge or gateway that screens out unwanted signals.

Xerox Builds on Ethernet's Success

Xerox plans to build on the success of Ethernet by extending the scope of the local-area network and by intergrating its products and networks with those of other vendors and with a wide range of public and private networks. According to Robert V. Adams, president of Xerox Systems Group, the plan calls for multiple local networks, ranging from Ethernet networks that offer a wide array of shared resources and capabilities to relatively simple networks and simple switching devices that serve the needs of small work groups.

"These networks may use a variety of physcial media, from twisted pair to fiber optics, in addition to the coaxial cable and its variants presently in use on Ethernet networks," Adams says. "By integrating Xerox networks and software with those of other vendors," he adds, "we are responding to the long-range requirements of customers and offering them more freedom of choice--through compatibility--in their selection and usage of equipment."

One new network option is a thinner (0.2-inch versus 0.4-inch diameter) coaxial-cable alternative to Ethernet that offers the same 10-Mb/s performance but allows closer machine spacing than does standard Ethernet. Also, in contrast to the in-the-wall Ethernet installations, the thinner cable is designed to run over the carpet or along the baseboard. Adams says the user-intallable cable provides a low-cost means of networking a few machines for a start-up installation, or adding PCs to an existing network. And, since it is fully compatible with standard Ethernet, the new cable can be used for portions of a larger Ethernet network.

To provide another networking alternative, Xerox has reached an agreement with AT&T to market the hardware used in the low-cost AT&T Starlan Network, which uses the spare telephone wires already in place in many office buildings. This approach is designed for people in small work groups, enabling them to share laser printers and hard disks on the network. While the AT&T Starlan Network runs at 1 Mb/s over standard twisted-pair telephone wiring, it utilizes the same basic control procedures as the 10-Mb/s Ethernet. Xerox says it will also provide a tie-in from the AT&T network to its other networking products running on Ethernet.

Meanwhile, the number of vendors producing Ethernet-compatible products and network supplies continues to grow. Many of these companies are in the process of implementing various Xerox Network System protocols, Adams says. In February, a number of organizations using XNS protocols formed the Xerox Network Systems Implementary Group (XNSIG), and a subgroup of the organization is working on developing a protocol to provide interoperability at the application layer. The next XNSIG meeting will be held in Palo Alto, California, on October 31 and November 1.

Last year, Xerox announced the availibity of its Interpress Printing Architecture, a set of protocols and formats that enable office machines from different manufacturers to work together for the first time to produce and distribute complex, high-quality business documents on electronic printers. More than 25 vendors have announced plans to use the standard as a means of achieving device-independent operation with printers of different types, makes and models. With Interpress, this device-independent printing can be performed regardless of whether the document contains text only or includes line-graphics, halftones or scanned images. Also, the user can print text and graphics on virtually any type of microprocessor-based printing device, including laser electronic laser electronic printers, facsimile devices, phototypesetters and plotters.

Digital Adds Broadband Option

In its role as joint developer of the Ethernet, Digital equipment is also helping to mesh the local network with its DECnet architecture. As p art of its network architecture, DECnet phase IV, Digital offers a number of products to connect the VAX-11 superminis, Unibus-based PDP-11 minis and Professional 300 computer systems to Ethernet. These products include a communications controller and supporting software, a transceiver and associated cable, and a line of Ethernet cables. Digital claims to have delivered close to 16,000 Ethernet nodes.

Last November, Digital became the first computer manufacturer to extend Ethernet to the broadband local-network environment by offering a broadband transceiver and associated frequency translator that are fully compatible wiht Ethernet. Digital subsequently announced an agreement with Sytek of Mountain View, California, to market broadband networks incorporating their respective network products to customers. Since Digital's broadband Ethernet products utilize a frequency that conflicts with some of Sytek's current LAN products, the two companies have been developing ways for the two product sets to co-exist on the same network. As part of this efort, Sytek has added a new option to its LocalNet 20 product line, the Group E modem, whose channel frequency does not conflict with Digital's Ethernal channel.

Digital's new broadband Ethernet transceiver, Decom, supports up to 1,024 nodes, and is available for both dual and single-cable broadband installations. When used in conjunction with the Delni clustering device, Decom provides connection to as many as eight DECnet/Ethernet devices. The broadband Ethernet frequency translator is used in conjunction with Decom in single-cable installations, and it enables a Decom to transmit at one set of frequencies and receive on another. In dual-cable installations, the translator is not needed, since the Decom can transmit and receive at the same frequency using separate connection points for each cable. The Decom is priced at $4,250, and the frequency translator at $4,500.

Digital's broadband and baseband LANs can be interconnected via DECnet routers. Likewise, the two types of LANs can be conected to other network environments via Digital's X.25 and SNA gateways. In August, Digital announced a new set of integrated services for broadband networks to complement existing baseband services. Like the baseband services, the brfoadband versions cover planning, installation and maintenance. In addition, the new services include features such as cable plant and channel certification that address the more-complex broadband network environment.

Component Firms target IBM, Apple

Component suppliers 3Com of Mountain View, California, and Interlan both began by targeting Digital systems and Ethernet, and both have since expanded their offerings to encompass IBM, Apple and other popular computers. Interlan expanded the services of its Net/Plus product line last november by introducing a network communications server/internet router that provides transparent data transmission between two physically separate Ethernets at speeds to 224 kb/s. It also introduced network-management utilities to run on an IBM and compatible Pcs, allowing network managers to control a large collection of network terminal servers and other Interlan servers on an Ethernet.

The Internet router lets users transparently initiate both interactive and file transfer sessions between nodes on two different Ethernets without having to know the overall network topology. Packets are routed across one or two dedicated synchronous data links using the Xerox Network Systems Internet Transport Protocols. The Internet router also allows Interlan's Ethernet Direct Connect for the IBM PC to access systems and resources on a remote Ethernet, and it supports file transfers between distributed PC, VAX/VMS and Unix systems. The Internet router is priced at $6,500; the $1,000 price for the network management utilities includes a PC-compatible Ethernet controller board and diagnostic software.

In March, Interlan merged with Micom Systems of Simi Valley, California. In the process, Interlan's Net/Plus LAN was integrated with Micom's Instanet data PBX to provide both low-cost terminal-to-computer communications and high-speed information exchange among otherwise incompatible personal computers, minis and mainframes. The combined product, known as Instanet/Plus, makes Micom one of the few vendors to offer PBX and LAN solutions to terminal access and inter-computer information exchange. The data PBX can support more than 1,500 terminals and computer ports, and the PBXs, can be interconnected for larger networks. In addition, it supports integral gateways to IBM SNA and bisync networks. Integral X.25 packet assembler/disassemblers provides access to and from packet-switched data networks. (Details on data PBXs will appear in the Datacomm Update on PBXs in the December issue of Communications News.)

Founded by Ethernet pioneer Robert M. Metcalfe, 3Com began by offering Ethernet transceivers and controllers to plug into Digital processors ranging from the low-end LSI-11 micros to the VAX-11 supermini. Today the firm's EtherSeries products interconnect personal computers and peripherals from a wide range of vendors, including IBM, Texas Instruments, Hewlett-Packard and AT&T, into Ethernet networks capable of supporting up to 1,024 personal computers with up to 2.5 km between the devices connected. In addition, 3Com offers network servers designed for different applications and numbers of users, along with network software that combines and extends the capabilities of network adapters and servers to provide functions that LAN users require. For instance, EtherShare software permits the sharing of a hard disk, while EtherPrint enables multiple users to simultaneously send data to a shared printer. Likewise, users can send and receive electronic mail through EtherMail.

For smaller networks, the company provides software that allows an IBM PC XT, or PC with a hard disk, to be used as both server and workstation. For higher performance, an IBM PC AT can be used. For even greater capability in larger networks, 3Com offers a multifunction 3Server network server, which combines an Intel 80186 microprocessor, 512K of random access memory and an Ethernet controller on a single board. The server is equipped with a 36-Mb formatter hard-disk drive, and can support six additional 36-Mb disks. As the 3Server's name indicates, the product is intended to support three networks: it currently serves both EtherSeries LANs and Apple computer's AppleTalk network, and it will support IBM's proposed token-passing LAN when the network becomes available.

In May, 3com introduced its Ether-3270 software to allow IBM PCs and compatible machines on EtherSeries networks to communicate with IBM mainframe computers using SNA protocols. The software transforms an IBM PC or 3Server into a communications gateway to the host computer. PCs on the network function as IBM 3278 or 3279 intelligent terminals, providing users with access to a variety of mainframe applications. The firm also announced a new line of software products, called EtherMac, that expand the networking capabilities of the Macintosh computer.

EtherSeries for Macintosh allows users on apple's appleTalk personal network to create and share files on the hard disk of a 3Server. The same 3Server can be connected to both an AppleTalk network and EtherSeries LAN, enabling Macintosh computers and IBM PCs to share information. Similarly, two AppleTalk networks can be linked to an EtherSeries network, which can then serve as a high-speed backbone LAN. A second EtherMac product, called EtherPrint for Macintosh, allows Macintosh users to perform spooled printing on an Apple LaserWriter and other printers through a 3Server. In July, 3Com doubled the disk storage on its network-server family with the introduction of the 3Server 70, which features a 70-Mb disk drive.

On the Bridging of LANs and WANs

Bridge Communications of Mountain View, California, also provides communication servers that connect computers and peripherals to the Ethernet network, as well as gateway servers for communication between Ethernet and other Ethernet, broadband, proprietary and public data networks. Last fall, Bridge introduced the first communications server to combine protocol conversion to the IBM SNA environment with full local-network connectivity and services, allowing asynchronous ASCII terminals to look like IBM 3278 terminals on demand. According to Bridge, the CS/1-SNA makes an ideal micro-to-mainframe link when used with IBM PCs or PC-compatibles equipped with the EtherLink network interface card from 3Com. Also, 3Com's EtherTerm software, designed for compatibility with Bridge network service, lets PCs access the CS/1-SNA emulation services, thus becoming 3278 look-alikes.

Bridge was also the first to offer an Ethernet Terminal server implementing the TCP/IP network protocols standardized by the Department of Defense. The CS/1 server with TCP/IP software performs the function of a terminal or host server, allowing up to 32 asynchronous devices to access host computers supporting TCP/IP that are attached to an Ethernet LAN. In July, the firm added to this development by introducing the CS/100-TCP/IP, a low-cost terminal server that links as many as 14RS-232 devices to a TCP/IP-based hosts and Bridge server-interfaced products with access to IBM SNA hosts over Ethernet.

At the same time, the firm introduced the first gateway that permits interconnection of two remote TCP/IP-based Ethernets. The GS/3-IP permits interconnection of up to eight physically isolated TCP/IP-based Ethernets over multiple point-to-point connection media, including leased or dial-up lines, fiber-optic and microwave links. Line speeds support the range of 1.2 to 64 kb/s, with data transfer between Ethernets at up to 175 kb/s. Along with the increasing use of larger LAN configurations comes the need for network management. Bridge's answer is the NCS/150 network control server, which provides a complete on-going record of all activity on the Ethernet network at the individual session level, even alerting users to critical conditions on the network.

"As LANs are configured for hundreds of users, having precise information about the activity of those LANs becomes essential," says Willia Carrico, president of Bridge. "For example, it's desirable to know who's connecting to whom at the individual session level, for security or accounting purposes. And, to balance the network load properly, you need to know if an individual server unit is handling too many sessions." The NCS/150 compiles a complete real-time audit trail of network activity that can be viewed on a display console or in hard-copy. The network administrator can also set "alarms" to monitor critical network parameters.

Among other getaway servers, Bridge offers the GS/4, which connects multiple Ethernets to form a LAN up to 40 km long, and the GS/6, which connects multiple Ethernets over a single channel of a CATV-based broadband network. The GS/6 marks Bridge's entry into broadband LANs, which was reinforced last March by its acquisition of Coherent Systems of Bedford, Texas. The first product from the re-named Bridge RF Products Division is an intelligent broadband modem that connects SDLC, HDLC or bisync devices over CATV cable networks. Model 8316 supports point-to-point or multi-drop connections at 56 kb/s on two-way broadband coaxial cable systems. "Until recently, most CATV plants were used primarily for video transmiision, with telephone lines being used for any data communications functions," claims Carrico. "The 8316 answers a growing demand that the data communications function be handled in a less-expensive way, over existing broadband network installations."

Systems suppliers Stress Universally

Ungermann-Bass was the first to ship an Ethernet-compatible system in 1981, and last year introduced the first commercially available fiber-optic version of the Ethernet Lan. The Santa Clara, California, firm currently offers four version of its Net/One system: a 10-Mb/s Ethernet-compatible baseband system, a 10-Mb/s thin coaxial baseband system, a 5-Mb/s CATV-compatible broadband version, and an Ethernet-compatible fiber-optic system. The Personal Connection, an extension of NEt/One for networking IBM personal computers, allows IBM PCs to connect to any host or peripheral device on the network.

In July, Ungermann-Bass increased its support of IBM systems by introducing two high-performance network interface units that allow 3270 temrinals and printers to communicate with IBM cluster controllers via the Net/One LAN. Network interface units are distributed communications processors that provide the physical interfaces and intelligence needed to permit communications betweeen a wide range of devices attached to the network.

Ungermann-Bass has also reached agreement with Microsoft to develop and market products enabling the Net/One Personal Connection products to be compatible with the IBM PC Network. Under the agreement, Ungermann-Bass will makret several versions of its implementation of Microsoft Networks, a software module that is incorporated in the IBM PC network and allows application programs running under MS-DOS to be shared among multiple microcomputer systems. The first releases are for Net/One products based on Ethernet and those compatible with Intel's OpenNet, which is based on the ISO reference model. In the future, the company will also be introducing versions compatible with the IEEE 802.4 token-bus and 802.5 token-ring standards.

Under the terms of another agreement, Wang Labs will integrate the Net/One broadband LAN products into its WangNet and FastLan local-area networks. In addition, Ungermann-Bass has formed an independent joint-venture company with General Electric to develop, manufacture adn market LAN systems for industrial applications. The new company, Industrial Networking, headquartered in Santa Clara, California, has been selected as a supporting communications contractor by General Motors/Electric Data Systems for an automation program within the GM Truck and Bus Division.

The project involves many robots, programmable controllers and computers that will communicate over a broadband LAN using the Manufacturing Application Protocol. In June, Industrial Networking announced it has successfully developed and produced the first VLSI chip set to implement the MAP specifications for factory communications. The two-chip set will provide the foundation of the company's product line, which is scheduled for introduction later this year, according to Joseph P. Schoendorf, president and chief and executive officer of INI.

Codex also supplies a general-purpose LAN available in baseband and broadband versions. The Codex 4000 Series Ethernet-compatible baseband LAN consists of transceivers, entryways, networking software and appropriate cabling, along with a Codex LAN manager. Entryways serve as intelligent nodes for interconnecting devices on the cable; the Codex 4001 entryway can accommodate up to four processor boards, each supporting its own I/O module, while the 4002 is a lower-cost version supporting a single I/O module. For the broadband LAN, the transceivers are replaced by RF modems, but since the entryways are media-independent, they can be used for broadband networks as well. In addition, the Codex LAN manager can be used on the broadband LAN with the addition of an internal RF modem card.

In January, Codex introduced several LAN products, providing a broad range of personal computer communications, resource sharing and internetworking on the Codex 4000 Series LAN. The new products offer:

* PC-to-PC communications, permitting the sharing of information and network resources with other PCs on the Codex LAN;

* PC-to-host communications, providing a micro-to-mainframe link that allows PCs to access corporate information-processing resources;

* Communications between PCs and one LAN and PCs, terminals and hosts on another LAN, when used in conjunction with local and remote bridges;

* PC-to-wide-area network communications, allowing PCs to access resources distributed throughout the corporate wide-area networks; and

* Management of the entire network from a single point of control.

For PC-based information and resource sharing in the local environment, Codex introduced two PC entryways, the Codex 4010 and 4011, which permit members of the IBM PC family and compatible units to connect to the network resources of the Codex LAN. The Mansfield, Massachusetts, firm also introduced PC software, called DiskTalk and PrintTalk, that provide PC workstations with the productivity benefits of sharing common data files, application programs and printers.

The Codex 4810 LAN manager provides the central point of control, allowing both local and remote management of the Codex LAN. It works with the firm's Network Operating Sysems Software Release 2.0, a menu-driven program that enables the network administrator to manage the network and allows IBM PCs and PC XTs to emulate dumb ASCII terminals and access others hosts on the network. In addition, Codex introduced an RF modem card to equip the manager for control of its 4000 Series LAN.

for internetworking between local and wide-area networks, the firm now offers the 4210 LAN SNA gateway, enabling non-SNA terminals and PCs on the Codex LAN to connect to an IBM SNA wide-area network. They also offer a more-general 4110 Muxport Gateway, which permits the internetworking of local and wide-are networks by enabling PC-to-host, terminal-to-host and terminal-to-terminal communications between a Codex 4000 Series LAN and a Codex 6000 Intelligent Network Processor-based wide-area network.

Net Uses Unique Access Method

Applitek of Wakefield, Massachusetts, offers a universal LAN that can provide both guaranteed and contention network access simultaneously on the same channel. Called Unilan, the network operates at 10 Mb/s and uses a unique access method called Unilink. When traffic on the network is light and the active devices are primarily asynchronous, non-intelligent terminals sending short, bursty messages, the network access is similar to Ethernet's. However, when synchronous devices or computers with regular, frequent traffic are added to the network, network operation dynamically adapts to provide token-passing-type guaranteed access, with bounded transmission delays to those devices. Also, in Ethernet-style operation, if traffic load increases collisions, then all devices on the network get guaranteed access.

Another aspect of Unilan's universality is its independence from the transmission medium. With the appropriate media access device, Unilan's network interface units can connect user devices to any of the commonly used networking cables, including optical-fiber, broadband or baseband coaxial cable. Similarly, the physical organization of cable, user devices and network interface units can be a bus or tree arrangement, whichever is most suitable for the environment.

On firm pioneering the use of fiber optics in LANs is FiberCom of Roanoke, Virginia. Its first product, WhisperNet, is an enhanced version of Ethernet implemented in fiber optics that reportedly meets or exceeds every specification in Ethernet and IEEE 802.3 standards. Whisper/Net allows the user to get an enhanced-distance Ethernet capability with all the benefits of secure optical-fiber cable, yet it costs on $490 per port. The linear topology is implemented as a rign with active nodes. Incorporating an optical bypass switch, a total of three consecutive nodes can be bypassed without affecting the network.

In August, the firm introduced WhisperRing, a fiber-optic network capable of extending a high-speed RS-422 twisted-pair LAN as far as 32 km, as compared to the 200-foot limit of wire systems. Again, WhisperRing employs an active ring topology with automatic optical bypass of a failed node. The active nodes convert lightwaves to electricity, then back to lightwaves. Their use is made possible by bypass switches that shut off a failed node, rather than the entire network.

AT&T, IBM Chart LAN Strategies

AT&T introduced its packet-switched local-area, the Information Systems Network (ISN) in June 1984. ISN uses AT&T's Premises Distribution system (PDS), a fiber-optic and twisted-pair premises wiring scheme, along with a collision-free architecture to provide high data throughput. At last May's ICA show in Dallas, AT&T unveiled several enhancements to ISN, which it says will be available for delivery in the second and third quarters of 1986. It also announced the general availability of its multifunctional Premises Distribution System and reported that three computer vendors, Hewlett-Packard, Wang and Xerox, have chosen PDS to support their voice, data, video and graphics communications.

Enhancements to ISN include synchronous support for IBM's Systems Network Architecture and other industry-standard protocols--including 3270-type terminals and cluster controllers--interfaces to Ethernet and the 1-Mb/s AT&T Starlan network, and a high-speed interpremises trunk to connect ISN packet controllers in a wide-area network. AT&T also provides an access-security feature that requires users to log on to ISN before they can use network resources. The Closed User Group feature allows the network manager to determine who can call whom on the ISN system. The manager can assign each network resource or endpoint on the network to one or more Closed User Groups.

AT&T's Starlan permits the interconnection of DOS and Unix-based machines, including the AT&T Personal Computer 6300, the AT&T Unix PC and the AT&T 3B2 computer. Starlan will support future AT&T MS-DOS and Unix workstations, and connections will be provided between Starlan and SNA, Ethernet and X.25 networks, as well as ISN, the firm states. To ensure the availability of applications software from independent software vendors, Starlan will also be made compatible with Microsoft's networks software.

Meanwhile, rumors abound of IBM's "imminent" announcement of its long-awaited token-ring local-area network. In a statement of intention issued in May 1984, IBM confirmed that the network would be based on the token-ring architecture it promoted at meetings of the IEEE 802 committee on local-area network standards. IBM also announced a cabling system designed t reduce the cost and complexity of installing or moving computer devices within a building. IBM explained that its token-ring LAN would be composed of the cabling system and "components planned for announcement at a future date."

In August 1984, IBM added a second statement of direction, saying that it will interconnect its token-ring LAN to two others, the IBM PC Network for communications between personal computers communicating on plant floors. Each network will have the ability to communicate with IBM's System/370 host computers and applications. The IBM PC Network is a low-cost broadband, peer-to-peer local-area network supplied by Sytek that enables IBM PCs, to share data and peripheral equipment, supporting distributed multi-user applications. For industrial applications, IBM intends to implement a broadband token-bus network that will connect the IBM Industrial Computer and other members of the IBM PC family on CATV coaxial cable.

The IBM Cabling System is permanently wired, with connections made to outlet plates in office walls. IBM estimates the cabling can pay for itself in a few years by eliminating most of the expense of moving workstations. The single cabling system can be used instead of coaxial, twinaxial, twisted-pair and other special cabling. Using a star topology, the system connects each office wall outlet to a distribution panel in a wiring closet. Wiring closets in the same building or different buildings on a campus can then be connected with either twisted-pair or optical-fiber cable.

For users unwilling to wait for IBM's LAN, Proteon of Natick, Massachusetts, offers a similar star-shaped token-ring network called ProNet. According to President Paul Rosenbaum, ProNet is already operating over the IBM Cabling System at Carnegie Mellon and a number of other installations. He adds that the firm is committed to making ProNet compatible with IBM's LAN when announced. ProNet operates at 10 Mb/s over a variety of media, including fiber-optic cable and twisted-pair, coaxial and twinaxial cable. Proteon offers host interface controller boards for Unibus, Q-bus and Multibus systems, as well as for the IBM PC. It also supplies boards for other computers from companies such as Gould, Harris and Perkin-Elmer. Up to 16 nodes can be connected to each wire center, allowing ProNet to operate as a star-shaped ring, increasing reliability and maintainability and simplifying the cabling. In addition, wire centers can be conneted to each other, forming a string of stars supporting up to 255 host nodes and 4,000 RS-232 connections.

In March, Proteon introduced ProNet-80, the first commercially availably token-passing, star-shaped ring network to transmit data at 80 Mb/s. Besides the high speed, the network reportedly offers a powerful error-detection mechanism and flexible host addressing system. ProNet-80 connects up to 240 Unibus or Multibus workstations using any combination of shielded twisted-pair or fiber-optic cabling. Since the new LAN is software-compatible with the firm's original 10-Mb/s network, now called ProNet-10, current customers can easily upgrade to the new ProNet-80 by replacing the original controller board and using the Unibus and Multibus host-specific boards.

Because of its 80-Mb/s operation, rosenbaum anticipates a variety of applications for ProNet-80, ranging from its use as a backbone network for several LANs, to a high-speed transmitter of complex high-resolution graphic data or as a super-fast host-to-host network. ProNet-80's error-detection technique not only detects errors, but also identifies their location. In addition, the system has the capability to perform group, subgroup and broadcast addressing, and it allows the user to change network addresses via software control.

Mini Suppliers Adapt to Multi-Vendor Nets

Token passing is also used by Prime Computer for its Primenet local network and by Apollo Computer for its domain system, both of which employ a ring topology, and by Datapoint for its Attached Resource Computer (ARC) local network. Up to eight Prime systems can be interconnected on Primenet, which operates a 8 Mb/s and permits a separation between adjacent systems of up to 750 feet.

Apollo's Domain system operates at 12 Mb/s. In July, the Chelmsford, Massachusetts, firm introduced a hardware/software package, called Domain/Bridge, that extends the functionality of the Domain system over long distances and allows users to connect multiple Domain systems into an integrated network. At the same time, the firm officially launched its open-architecture program with an initial set of products aimed at users of IBM and Digital host computers and IBM PC and compatible units. The firm also announced its commitment to the adoption of industry standards, including support for the ISO reference model and the extension of Domain architecture's data and resource access to mixed-vendor environments.

Apollo also plans to interconnect multiple Domain networks to one another over a variety of industry-standard networks such as Ethernet. Among the initial set of products in the program are domain/SNA, which provides communications links with IBM computers operating under SNA; Domain/PCI, for communications with IBM and compatible PCs; and Domain/Vaccess-1, which provides communications links with Digital VAX/VMS computers.

Datapoint's ARCnet employs baseband transmission over coaxial cable at 2.5 Mb/s. While it operates logically as a bus, any physical topology can be used as long as no loops are formed. Last year, Datapoint made a major change in its marketing and development philosophy by announcing its intention to open the proprietary ARCnet to industry-standard technology. The first manifestation of the new philosophy was the introduction of a networking package for the IBM PC and a software package enabling ARCnet to support CP/M software applications.

The package for the IBM PC and PC XT consists of networking components, software, file servers and a new adapter card designed to fit in an expansion slot of the IBM PC. Depending on user requirements, the package can alos include Datapoint file servers, print servers and communications servers. Datapoint has also introduced a direct network interfacefor its Vista-PC color professional computer.

In August, the San Antonio, Texas, firm added to its Pro-Vista line of office automation software a package called Vista-Telex that allows users at workstations in ARCnet networks to perform telex functions as well as word processing, electronic mail and business applications. Datapoint has also introduced a 32-bit computer with a Unix-like operating system, called Unos, that will be marketed as a stand-alone system as well as an additional resource on ARCnet. The Datapoint 3200 supports a relational data-base management system and the Databus development language.

Among other minicomputer vendors, both Hewlett-Packard and Data General support the General Motors Manufacturing Automation Protocol. HP's local-area network is based on, and is compatible with, the IEEE 802.3 standard. The HP LAN 3000 uses a bus topology with CSMA/CD access method to interconnect HP 3000 computers with a transmission rate of 10 Mb/s over the coaxial cable.

In January, Data General announced its support for the Xerox Network System Internet Transport Protocol under its AOS/VS operating system, along with support for the Transmission Control Protocol/Internet Protocol (TCP/IP). It also announced an intelligent LAN controller for its Eclipse MV/Family systems using an IEEE 802.3-standard interface. Data General also offers an Ethernet segment repeater and an intelligent broadband controller manufactured by Ungermann-Bass and designed to connect DG's Eclipse MV/Family computers with U-B's Net/One broadban LAN.

Under an agreement between the two companies, Ungermann-Bass sells to Data General customers the components of the Net/One broadband local-area network and provides network design and documentation for Data General customers. In turn, Data General is free to market the intelligent broadband controller.

"With this arrangement, Data General can now offer customers both broadband and baseband local-area networking solutions," notes Joseph Forgione, product marketing manager of Data General's Information Systems Division.

In contrast to most of the other computer vendors, Wang Labs employs broadband technology in its WangNet local network. Last year, the Lowell, Massachusetts, firm introduced a user-installable version of WangNet geared to small and medium-sized organizations. Called WangNet FastLan, the cable system implements the full communications capabilities of WangNet on fixed lengths of cable that provide consistent RF signal levels. This eliminates the lengthy decision and certification procedures of WangNet, which uses a different type of cable, shortening the installation time and reducing the cost. As with the custom-designed WangNet, FastLan uses a dual-cable broadband medium and CATV components for the concurrent exchange of data, text, image and video information.

In April, Wang Labs introduced the WangNet Shared Interconnect Modem Service (SIMS) as an inexpensive means for connecting groups of standard asynchronous terminals, PCs and printers to each other and host processors via WangNet. It allows as many as 2,000 devices to attach to WangNet at costs as low as $500 per port. SIMS provides switching capabilities that allow users to og on to any compatible system on the network. It supports data rates to 19.2 kb/s and uses the Carrier Sense Multiple Access scheme to resolve contention.

Wang was scheduled to introduce two further services in September: the PC-Net Service, for running the IBM PC network on WangNet and FastLan, and the 802.3 System Service, which allows up to five 802.3-compatible networks to run on WangNet and FastLan. For the PC-Net Service, a user buys an adapter for each IBM PC to be attached to the network; the adapter plugs directly into the IBM PC and the WangNet or FastLan wall outlet. Similarly, any device with an 802.3 controller can be attached to the firm's new 802.3 adapter, which in turn plugs into the WangNet or FastLan wall outlet. A single adapter allows up to five 802.3-compatible networks to run on WangNet/FastLan.

Broadband Systems Gear Up for Growth

One of the leaders in broadband technology is Sytek, which has an installed base of more than 800 LocalNet 20 networks serving more than 160,000 user devices worldwide. LocalNet 20 is an open access LAN, which allows users to interconnect any combination of computers, terminals and other devices that support RS-232 interfaces. The LocalNet 50 products implement optional higher-level functions, such as access control, monitoring, failure-isolation and security. These products also handle inter-network linking functions and long-distance gateways.

In June, Sytek introduced the 5101 Network Control Center as an upwardly compatible replacement for its LocalNet 50/100 NCC. Intended for use in moderate to large Sytek LAN installations, the 5101 automates and enhances network management by centralizing network information, control and monitoring in a single unit. Its new hardware base and software capabilities enable a variety of broadband devices, including printers, terminals and hosts, to be managed as a unified communications system.

S ytek also designed and currently manufactures key components for IBM's PC Network, which is based on the LocalNet open system architecture. In July, the firm announced the Sytek 6050 network trnaslator as the first member of its planned 6000 family of IBM PC

Network-compatible products for large PC networks. Serving as an enhanced functional replacement for IBM's Translator Unit, the 6050 reportedly eliminates the device and distance limitatons imposed by the IBM PC network. IBM's Network Translator, in conjunction with the IBM Cable Kit, is designed to support PC communications on a network of up to 72 nodes and distances of up to 1,000 feet; the Sytek 6050 can support PC communications on a network of up to 1,000 nodes and distances of up to a three-mile radius. In addition, the 6050 can co-exist on a cable system that supports many services, such as voice, video and data.

Since, the 6000 family is an extension of the LocalNet open architecture, LocalNet 20 networks and Sytek's PC networks can co-exist on the same cable system. "This is a big plus for managers who are looking for ways to manage the growth of personal computers while taking networking investments," states Duane Bowman, product line manager for the 6000 family. Also, the 6050 offers adjustable gain, which allows PC networks to co-exist on non-Sytek broadband systems. The 6050 is compatible with single and dual-cable systems and connects to a brandishing-tree topology so that failure of a single node has no effect on the rest of the network.

One of the newcomers to the commercial broadband LAN scene is TRW, whose Information Network Division was established in April to market the firm's Concept 2000 line of broadband LAN products to the commercial marketplace. In fact, TRW, through its Electronics and Defense Sector, has been in the LAN business for more than a decade, creating and delivering turnkey systems chiefly to the government.

The Concept 2000 line comprises hardware and software components that permit the interconnection of asynchronous and synchronous devices, baseband and broadband networks, and networks with different protocols. Utilizing broadband coaxial cable bus technology and a CSMA scheme, the systems can link virtually any combination of terminals, computers and peripherals used in business and institutional settings, the Torance, California, firm claims.

The building block of the Concept 2000 line is the Intelligent Connector Unit (ICU). A modular interface unit, the ICU can link together different transmission media, access methods and higher-level protocols, and can be configured for dual-cable non-translated or single-cable translated systems. The ICU connects to standard CATV cable with a bus topology that can be expanded to accomodate as many as 20,000 users. It is available in both dual and four-port configurations and accomodates a variety of interfaces, including RS-232 and current loop.

Networked PCs Get IBM Blessing

IBM's PC Network may have "legitimized" the concept of networking micros, but outside of Ethernet and the PC Network, there is little standardization yet in this aspect of local-area networking. Major players include Corvus Systems of San Jose, Nestar Systems of Palo Alto, and Novell of Orem, Utah.

Corvus claims to have the largest installed base of networks in the world, with more than 150,000 nodes connected on over 18,000 of its Omninet networks. Omninet is a baseband network that operates at 1 Mb/s over a twisted-pair bus with a Carrier Sense Multiple Access/Collision Avoidance scheme. It can accommodate 64 nodes and a maximum network length of 4,000 feet. Omninet supports IBM PC and compatible models, as well as micros from Apple, Digital Equipment, Texas Instruments, Zenith and Sony. In addition, the network accommodates the firm's own Concept personal workstation and all other Corvus products. Further, a number of major suppliers, including NCR, Sperry, Honeywell, Radio Shack, olivetti, NEC and Sony, have licensed Omninet for use with their systems.

Corvus also supplies bridges to other networks and gateways to mainframe computers. Its SNA Gateway, for instance, links an IBM PC-based LAN to a remote IBM mainframe. Unlike other schemes where the networked PCs emulate 3278 terminals, Corvus SNA gateway allows the PC to retain its ability to perform local processing functions, as well as acting as a terminal to access files, electronic mail, host applications and data bases. Corvus has also licensed Microsoft Networks for use on Omninet, allowing Omnineted micros running MS/DOS 3.1 to share application software.

Second Vendor Supports Microsoft

Nestar also supports Microsoft Networks and offers an IBM SNA gateway as part of its Plan series of local-area networks. The gateway allows a dedicated IBM PC on the network to emulate a remote IBM 3274, supporting up to 16 user stations per gateway. Plan employs a baseband token-passing architecture using ARCnet protocols for the physical and data-link layers, combined with the Xerox XNS protocols for the network and transport layers. The network medium may be 3270-compatible coaxial, fiber-optic or the IBM Cabling System cable. Data is transmitted at 2.5 Mb/s.

With the March release of its NetWare Netbios Emulator, Novell also supports the IBM PC network and Microsoft Networks. The IBM PC Network program uses the Netbios protocol for communications across the network. When Novell's Netbios Emulator is resident either in software or firmware in a local-area network, all the Netbios commands are fully supported. Said to "serve all LANkind" by its creators, the Novell NetWare operating system brings file-server flexibility and multi-user functionality to 26 LANs.

For Research targets the IBM PC family with its 10-Net Ethernet-compatible local-area network. IN May, the Dayton, Ohio, firm announced an enhanced 3270 SNA gateway that allows the networked PC to act as a 3274 cluster controller. Up to 64 active SNA sessions can be supported on a single 10-Net LAN, and a PC communicating through the gateway can have between one and four simultaneous active SNA sessions.

Compared with the considerable hardware effort, relatively little development work has been done to date with network PC software. Besides Novell, one of the software pioneers is Software Connections of San Jose, which claims to have been the first company to market a relational data-base management systems specifically designed for the PC-based LAN market. Datastore: Lan allows several users on the network to share the same data-base file at the same time.
COPYRIGHT 1985 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1985 Gale, Cengage Learning. All rights reserved.

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Author:Edwards, M.
Publication:Communications News
Date:Oct 1, 1985
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