Local Area Networks in the Midrange Environment

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Brief: LANs allow users to expand their computing power beyond the desktop and to share resources with other users to reduce overall costs. With proper planning, LAN technology can be added to your AS/400 environment to give your users the best of both worlds. This article offers MIS managers a strategic overview of the planning process for this type of project.

A friend of mine-let's call him Q-is an MIS manager for a manufacturing organization that has a problem.

Q's computer environment has been segregated for about a year. Most users are attached to the AS/400 through twinax cable. Last year, about 20 rebels from the Engineering department snuck a local area network (LAN) into their budget. Now, they're happily running computer-aided design (CAD), word processing and spreadsheet applications from a networked file server. The AS/400 people have no use for a network, and the network people have no use for the AS/400. That scenario is about to change.

The president of the company is impressed with what the Engineering department can do with its E-mail package. He wants everyone to use networked E-mail to cut down on paper. He also wants Engineering to join the rest of the company in using the software on the AS/400. His question: Why can't we run both networked and AS/400 software from the same PC? The president appoints Q to tackle the project and to report what the company's next steps should be.

Are You Q?

Does this sound familiar? This scenario could describe any number of companies. Like many MIS managers, Q is an AS/400 expert. He's kept an eye on PC technology-he even has one on his desk-but he's never touched a network.

This article is written for all the Qs in the world: those AS/400 MIS managers who have to incorporate LAN technology into their MIS strategy. Too complex and costly to implement on a departmental basis, the coexistence of LAN and AS/400 technology has become a project for the MIS department.

But what is a LAN? A LAN is a communications network used to link computers and peripheral devices (e.g., printers, CD-ROMs and modems), within a small geographic area such as a building or a campus. (Definitions of network terminology used in this article are included in the Glossary on page 67.) LANs are used for three main reasons.

1. LANs let PCs share devices that may be too expensive to dedicate to one PC. (This was what LANs were originally designed to do.) For example, an expensive laser printer or CD-ROM drive can be accessed by anyone in the network.

2. LANs allow anyone in the network to access databases and programs that reside on what is known as a file server or client server. This is usually the fastest and highest-capacity PC in the network. A centralized database can reduce information redundancy and simplify the management of your information (e.g., administering security and performing file backups). Purchasing a single network version of your software can be less expensive than buying single-user copies for each computer on the network.

3. A LAN allows anyone in the network to send messages and work jointly with others on the LAN.

How do you prepare to include your AS/400 in a LAN? What hardware and software pieces need to be in place? And what's the role of PC Support in all of this? This article shows you the LAN-to-AS/400 landscape from 30,000 feet, as if you're flying over it in an airplane rather than crossing it on foot. This approach gives you the concepts for LAN-to-AS/400 connectivity without bogging you down in details.

So fasten your seatbelts and please stow all your carry-on luggage in the overhead bins or under the seat in front of you. The AS/400-to-LAN connectivity aerial tour is about to begin.

Let's Not Talk About Cabling Just Yet

In your current environment, the AS/400 may be the center of the universe. From a LAN perspective, the AS/400 acts as a file server-perhaps one of many. Q or any other AS/400 manager needs to ask three questions before implementing a network with an AS/400 as one of the file servers. Like a flight plan for a pilot, the answers to these questions determine the route to be taken and the types of equipment you will use.

1. Who will use the network and what information will the user need to access?

You can define the scope of the network by addressing this first question in detail. What file servers will it include? Will all users be located in the same building or campus, or will they be spread across the continent? What type of information will be accessed? The answer to this question is determined by your business needs and how you believe a network will solve them.

2. What kind of physical architecture is needed to make the proposed implementation work?

This question's subtopics include how to connect each location, identifying additional equipment that may be needed, accessing file servers over a large geographical area and designing the network for future growth. This question deals with the overall physical design of the network, the backbone system your users will plug into. It identifies the capital investment in equipment required to make your plan work. This is important because upper management will definitely scrutinize your capital requirements very closely.

3. How does each user access the information he needs on the network?

This deals with network compatibility and machine configurations. How will each workstation and file server tap into the network? What types of workstations will be needed? What software and files will be shared between users? The question of user access is the most specific of the three, because it deals with how individuals relate to the network.

Although there is no detailed checklist you can follow for building a LAN-to- AS/400 network, these three questions offer a simple methodology for starting the network design process. You'll see that it really isn't much different than any other system you've designed in the past.

To build a network, you simply start with your basic business needs, survey the available technology, make decisions based on needs and available capital, and implement accordingly. It sounds easy from 30,000 feet, but many details must be resolved before you can design a solution. Once you have a firm grasp of the issues, one question will lead to another, which will lead to a plan and eventually an implementation.

Square One

To start with, our prototypical AS/400 manager, Q, needs to understand what he's implementing. AS/400 managers often encounter confusion in this area because it's hard to get a high-level overview of the problem at hand.

Technical documentation usually doesn't cover the big picture. Articles tend to be specific, working on the assumption that the budget for LAN and AS/400 coexistence has already been allocated and the project is underway. You usually don't find articles detailing why you want to accomplish this or even what a network of this type would look like.

The easiest way to begin understanding LAN and AS/400 connectivity issues is to define the differences between running the AS/400 over twinax and running it over a LAN.

One-to-One Versus One-to-Many

1 illustrates the differences between twinax and LAN workstation connections for the AS/400. When you access an AS/400 from a dumb terminal over twinax cable, you're establishing a one-to-one connection between the two machines.

Figure 1 illustrates the differences between twinax and LAN workstation connections for the AS/400. When you access an AS/400 from a dumb terminal over twinax cable, you're establishing a one-to-one connection between the two machines.

In contrast, when a PC is connected to a LAN, you're establishing a one-to- many connection. Like a commuter railway line, the AS/400 and your PC are considered to be separate stops on a common track. This track, also known as the network media, can take such diverse forms as Ethernet, token-ring, fiber- optic cable, or a number of other options. Rather than wiring your PC to the AS/400, you connect it to a central location in the network. This location is usually a hardware device called a concentrator. From the concentrator, you can send information to any other computer attached to the concentrator.

The capability to access several machines over the network media gives your users tremendous flexibility. For example, if you dedicate a specific machine to creating and sending faxes, your users can sign on to it and send faxes. They can also sign on to an AS/400 for access to your core business applications. PC modems and printers can be pooled for reduced costs and greater efficiency. Special equipment, such as high-speed computers which run stress testing or statistical analysis, can be accessed. The network allows your users to expand their computing power beyond the desktop to the resources they need to get their jobs done.

Networks can be as large or as small as you need them to be. LANs are not limited to a single building or location. They can be spread out to encompass an entire set of buildings, a campus or even a city. In this case, the network is referred to as a metropolitan area network (MAN). Networks with computers or file servers separated by greater distances-spanning different cities or states, for instance-are called wide area networks (WANs). When networks spread out to include distant locations, their network media may change. For MANs or WANs, media types may include radio waves, microwave links, high-speed telephone lines, fiber-optic cables and satellite links.

In a network scenario, the AS/400 becomes just another file server to be accessed as needed. The AS/400 will remain an important tool in your MIS strategy, but it's no longer the center of your users' universe.

How Do You Do It?

Now that we've reviewed some of the broader aspects of connecting an AS/400 to a LAN, let's talk about some of the specific work involved.

Even though you may be running several different types of devices over the same network media, all of them have one thing in common. Each one is attached to the network by virtue of network media (think of it as a wire) and a network interface card (NIC). Whether the machine is an intelligent workstation, a UNIX file server, a Novell NetWare file server, an AS/400, or an E-mail server, it always has these two elements.

1. The definition of the first element (network media) is very flexible. The media could be an Ethernet or token-ring cable. It can consist of telephone lines, radio waves, microwave links, or fiber-optic cable. The media is simply the vehicle which delivers the information that flows through your network. This information is what allows your workstations to access all of the attached file servers on the network, including the AS/400.

In any local, metropolitan or wide area network, it's possible to have mixed network media between different sections of your network. A network that includes file servers in Chicago, New York and Toronto could use token-ring as the network media in Chicago and Ethernet in New York and Toronto. The three locations could be attached through a combination of microwave and T1 telephone lines.

2. The second element (the NIC) functions as the workstation or file server's local passport to the network. Every machine must have a NIC to run on the network. Without it, network access is impossible. The network media must be "attached" to that card. Attachment can be direct, as in the case of Ethernet or token-ring cable; or it can be indirect, as in the case of a NIC that receives information through radio waves or microwaves.

The AS/400 is very flexible in the type of NICs that can attach to it. IBM and third-party vendors offer Ethernet, token-ring, FDDI and TCP/IP cards that allow your AS/400 to interface to a LAN. A NIC works in conjunction with a line description on your AS/400 that controllers and devices can make use of.

Network media is a smart alternative to standard twinax cabling because it allows users to access several file servers without sacrificing access to the AS/400.

Other Pieces of Equipment

Something that strikes you immediately when you plan a network is the number of hardware issues you must address. The network media and NICs covered so far are by no means the only additional pieces of equipment you'll need. A standard network configuration may also include concentrators, bridges, routers and brouters. Let's review each of these items in turn.

A concentrator, sometimes called a hub, acts as a wiring center for the network. By providing this central point, the concentrator allows different network segments or workstations to communicate with each other.

A bridge is a device that forwards data between networks. For example, a bridge may be used to provide translation of the data from token-ring format to Ethernet and vice versa.

A router controls the flow of information between different network segments. Routers can find the best route between any two networks, partition a network (to reduce unwanted network traffic) and more.

A brouter is what the name implies: a cross between a bridge and a router. A brouter combines the dynamic routing capability of a router with the interconnection capabilities of a bridge.

2 shows an example of how a network might be tied together using these various pieces of equipment. For more information on bridges, routers and brouters, see "Internetworking and the AS/400" in this issue.

Figure 2 shows an example of how a network might be tied together using these various pieces of equipment. For more information on bridges, routers and brouters, see "Internetworking and the AS/400" in this issue.

PC Support-The Final Piece?

At this point, Q is wondering when he'll be able to deal with the AS/400, which is closest to his heart. When you're working with a network, it's easy to forget the important role the AS/400 plays in all of this. For most companies, the AS/400 is the workhorse of the organization. It typically runs core business applications, such as accounts receivable, invoicing, shipping and manufacturing. It's vital that as many users as possible be able to access this file server.

Accessing the AS/400 (and other file servers) from a single PC can be frustrating. Although it is not always the final product selected, IBM's PC Support software usually constitutes the first choice for MIS departments combining AS/400 and network functions.

Earlier, we discussed connecting your workstations to a network for file-server access. We never discussed why you'd want to run PC Support over the network. If you only want to run AS/400 terminal emulation, there are much better ways to do it. So, how does networked PC Support benefit your LAN environment?

First, it allows you to run all your networked applications, including those on the AS/400, from a single device (your PC). PC Support brings other features to the table as well. It provides AS/400 printer support for your PC printers and virtual printer support that lets you print PC reports on your AS/400 printers. Additionally, it supports data queues, file transfer between the AS/400 and your PC, and shared folders to access AS/400 DASD as if it were a drive on your PC. Many third-party packages offer some of these features, but none offer the breadth of services IBM provides with PC Support.

In the Chicago-New York-Toronto example, the networks in each of the three cities ran either token-ring or Ethernet. These are two of the most common configurations for LAN media, and IBM has provided additional software to run PC Support over these networks.

PC Support by itself is unable to interface with most network operating systems (NOS). To do this, you may need to purchase an additional software package from IBM called LAN Support. Using LAN Support, you load additional network drivers on your PC to control the way data is transmitted through the NIC. LAN Support works hand in hand with PC Support to format information for network use. It takes control of your NIC and uses it to transmit information across the network. The LAN Support program will only work with specific IBM-tested NICs listed in the LAN Support manual.

Using LAN Support and PC Support together allows you to access the AS/400 over network media and to run programs locally from your PC at the same time. This configuration will work equally well whether you are running straight DOS PC Support or PC Support under Microsoft Windows. If you are running Windows, you also need to run PC Support V2R2 or above. With V2R2, IBM made significant improvements in memory management. This corrected many of the problems earlier versions of PC Support had with Windows compatibility.

The LAN Support/PC Support configuration described here, however, does not allow you to access other network file servers along with the AS/400. Running PC Support and a NOS, such as Novell NetWare, from the same PC is called coexistence. To describe this concept further, we'll limit the discussion to Novell NetWare 3.11 since this is presently the most popular NOS.

PC Support and Coexistence

IBM's LAN Support program takes control of the NIC on your PC. When you try to log into a NetWare file server, the NetWare log-in software also tries to control the NIC on the PC. The NIC must be controlled by one set of PC drivers, and both programs cannot access it at the same time. An accommodation must be made so that NetWare information can run over the NIC while LAN Support controls it or vice versa. This is the coexistence problem.

IBM has come to the rescue for AS/400 and Novell NetWare coexistence. If you intend to access these servers concurrently, pick up IBM's redbook, Using DOS PC Support/400 with Novell NetWare 3.11 and Net-Ware for SAA 1.3 (GG24-4013). In this book, IBM gives several configurations for running PC Support alongside Novell NetWare 3.11 in both Ethernet and token-ring environments. If you are attempting this project, this book is mandatory reading.

Unfortunately, not much specific help is available for coexistance with NOSs other than NetWare 3.11. For example, Novell NetWare 4.0 presents an entirely different set of challenges than NetWare 3.11. If you have a NOS other than NetWare, such as Banyan VINES, you may have to do some research to get your coexistence answers.

Existing PCs present another concern with coexistence on a network. Q's situation began with a group of rebel users who started their own network and now need to add AS/400 connectivity to their workstations. These workstations present their own group of problems. As we discussed, LAN Support is recommended for use with a specific group of NICs. IBM does not officially support cards that are not listed in the LAN Support manual, and chances are good that the Engineering department didn't use a NIC from that list. When expanding a network or creating a new network that will include the Engineering department's machines, Q will also need to evaluate what changes need to be made to bring them in line (e.g., compatible NICs, upgrading hardware or memory, company software standards) with the new environment.

There is one final but very important note on coexistence. Depending on the configuration you are using, you might introduce some performance issues with LAN and AS/400 coexistence. 3 illustrates two different ways you can configure a workstation for AS/400 and Novell coexistence. In one configuration, Novell controls the NIC, resulting in good NetWare performance and a loss of PC Support shared folders performance. In the second configuration, LAN Support controls the NIC, yielding good shared folders performance. Yet, Novell NetWare performance may suffer a degradation of 10-15 percent because it is running under LAN Support. You need to be aware of the trade-offs as you design your network.

There is one final but very important note on coexistence. Depending on the configuration you are using, you might introduce some performance issues with LAN and AS/400 coexistence. Figure 3 illustrates two different ways you can configure a workstation for AS/400 and Novell coexistence. In one configuration, Novell controls the NIC, resulting in good NetWare performance and a loss of PC Support shared folders performance. In the second configuration, LAN Support controls the NIC, yielding good shared folders performance. Yet, Novell NetWare performance may suffer a degradation of 10-15 percent because it is running under LAN Support. You need to be aware of the trade-offs as you design your network.

Other Players

Ultimately, PC Support alone may not be your answer for AS/400 connection in a network. Other options include RUMBA, a Windows-based AS/400 connection product from IBM and Wall Data, and offerings from several other vendors that claim to solve many coexistence problems. Novell offers NetWare for SAA, which runs PC Support sessions through a NetWare file server without the need for the PC Support router.

The marketplace is big and solutions are many. A little bit of research may yield one that is right for you.

In addition to the information listed here, a new software package may have an impact on LAN-to-AS/400 connectivity. IBM's recently announced LANRES/400 package allows you to manage network files, including Novell NetWare files and directories, directly from the AS/400. This is a part of the network picture that has been missing, and its appearance may alter some thinking on how to manage a network. (For more information on LANRES, see this month's Client/Server Spotlight.)

So, is Q Finished?

At this point, Q should have a basic feel for what's involved in setting up his network. He's gained some 30,000-foot knowledge in defining the scope, architecture and connection needs of the project he's been assigned. Obviously, this isn't the same as knowing what to do in his particular situation, but it's a start.

Q's task at this point is to build on this knowledge base and apply it to his environment. For specific information, the public library or his local bookstore is a good place to start. Hardware and software vendors present seminars and offer advice on building a network. This advice can be obtained for a fee or, in certain instances, for free. If Q is willing to sit through a few sales pitches, he can pick up some valuable information for getting through this process. Other seminars may cost a little more but are definitely worth the price.

The job now is one of education and implementation. After flying through the basics, it's time for Q to put his feet back on the ground and build his network. For Q and a number of other AS/400 managers, the job is just beginning. It's an exciting challenge and it's time to get started.

Joe Hertvik is an AS/400-LAN system administrator and freelance writer working outside of Chicago.

Editor's Note: For more specific information on how to configure Novell NetWare and AS/400 coexistence, you can also read Joe Hertvik's article in this month's PC Support Expert newsletter, "PC Support and NetWare on the LAN."

REFERENCES

Local Area Network Guide (SC41-0004, CD-ROM QBKA1G02).

PCS/400 Coexistence with NetWare and Windows (GG24-3637, CD-ROM GG243637).

Using DOS PC Support/400 with Novell NetWare 3.11 and NetWare for SAA 1.3 (GG24-4013, CD-ROM GG244013).

Glossary

Bridge: Device that connects LANs using similar or dissimilar media and signaling systems (e.g., Ethernet, token-ring and X.25).

Brouter: A device that combines the dynamic routing capability of a router with the ability of a bridge to connect dissimilar local area networks.

Coexistence: The ability of PC Support and a local area network operating system such as NetWare to run simultaneously on the same PC.

Concentrator: An access unit (hub) that allows network devices to be connected through a central point.

Ethernet: The most commonly used protocol for establishing local area networks.

FDDI (Fiber Distributed Data Interface): An ANSI-standard, 100Mbps, fiber-optic local area network. It is also capable of running on twisted-pair copper wire.

File server: A device on a local area network that allows users to access files.

Local area network (LAN): A data communications network made up of computers and devices confined to a limited geographic area.

Network driver: PC software that controls the flow of information between the PC and the local area network.

Network interface card (NIC): A printed circuit board that connects a device to a network.

Network media: The medium over which network information travels.

Network operating system (NOS): The software that controls network operations.

Metropolitan area network (MAN): A network that covers a larger geographic area (typically within a city) than a local area network.

Router: An interface between two networks that provides network-management capabilities such as load balancing and finding the best route between the networks.

TCP/IP (Transmission Control Protocol/Internet Program): A set of protocols developed by the Department of Defense for the purpose of linking dissimilar computers across many kinds of networks.

T1 telephone line: A digital telephone line with a capacity of 1.544Mbps.

Token-ring: A protocol in which an attached workstation must receive a token before data can begin transmitting.

Wide area network (WAN): A network that covers a larger geographic area than a local area network or metropolitan area network. WANs typically span cities, states and countries.


Local Area Networks in the Midrange Environment

Figure 1 Twinax Versus LAN Implementation for the AS/400

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Local Area Networks in the Midrange Environment

Figure 2 How Two LANs Can Be Linked to Form a WAN

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Local Area Networks in the Midrange Environment

Figure 3 Two Approaches to Providing AS/400-Novell NetWare

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