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Building an expandable network; planning ahead will save you headaches later as your Mac network grows

Douglas E. Welch

Macworld, May 1993 v10 n5 p120(7)

COPYRIGHT Macworld Communications Inc. 1993


The design of most Macintosh networks belies their bootleg history. At many companies, Macs were brought in through the back door and were not supported by the company's technicians and computer managers. This meant that the average Macintosh network first consisted of a connection between one Mac and its printer. Frequently the next step was to connect a few more devices in a daisy chain so that people could share the printer, but little else was usually done. Although Apple has always had a LocalTalk wiring standard, most people opted to connect network devices with low-cost LocalTalk connectors (usually Farallon Computing's PhoneNet Connector) and standard phone wire. That cheap, ad hoc solution helped everyday users solve the basic problem of connecting Macintoshes and peripherals.

Macs are now an important part of corporate life, and LocalTalk is no longer sufficient for the large Mac networks in corporate environments. Still, a little planning can help anyone turn an ad hoc Mac network into a full-fledged, high-speed communications highway that everyone can use. The following tips for five basic areas of network design should put you well on your way to building that highway.

1. Upgrade the Wiring

AppleTalk, the built-in protocolused on LocalTalk networks, was designed to be used on a variety of wiring types, including the standard phone wires that run through most office walls. But such wiring can cause problems, such as lost data, and can severely limit expansion of the network.

Problem

In most cases, especially in a rented space, the wiring is owned by the landlord, not the tenant. Modifications to this wiring may be difficult to perform or even prohibited by the owner. Also, it is often difficult to find accurate wiring diagrams. Installation, maintenance, and troubleshooting can become a nightmare without basic information about where the wires are in the walls and how they are spliced and terminated.

The costs of maintaining a phone-line-based network are extremely high when you factor in the amount of wasted support time and lost productivity when the network fails.

Solution

When planning for new wiring in an office or building, consider future uses. Some unused areas may later become offices, printer stations, or cubicles--where you'll want to have nodes. Wire all areas at installation time so that you can extend the network to those areas as you convert them from unused space to someone's desk or printer space.

Problem

The line quality of internal phone wiring is an unknown. Poor-quality wire makes it difficult to expand a network to provide for higher-speed protocols like Ethernet or Token Ring. The AppleTalk protocol, partly because of its slow transfer rates and protocol design, works well over lines of uneven quality. But higher-speed protocols are more sensitive to line quality. If the wiring is poor, networks based on these protocols can experience unacceptable errors during data transmission or can even cease to function.

Existing phone wiring may work fine for 20 or 30 devices, but device number 31 might cause problems across the entire network. So, while phone wiring can be used to start a network, it is in everyone's best interest to develop plans for using dedicated network wiring to support future growth. By providing your data with the best possible path to follow, you will be creating a good foundation for the rest of the network.

Solution

Select the proper type of wire. United Laboratories (known best for the UL fire-prevention certification seen on many devices) provides a five-level standard for deciding which type of wire fits your present and future needs. Level 1 is for data rates below or equal to 200 kilobits per second (Kbps), which is the transfer rate of a standard LocalTalk connection; Level 2 is for 4 megabits per second (Mbps) and slower; Level 3 is for 20 Mbps and slower (Ethernet's 10-Mbps speed fits in this level); and Levels 4 and 5 are for speeds of up to 200 Mbps.

Tip

Wall jacks are rated by using the same system as wires use. Make certain that you match, for example, Level 3 wire with Level 3 wall jacks, or Level 2 wire with Level 2 jacks.

Tip

Put in more wire than you think you need. A good rule of thumb is to install 1 1/2 times the wiring needed to support the current usage. This gives you room to grow and offers flexibility in network setup. For example, LocalTalk cabling requires two wires (one pair), Ethernet requires four wires (two pairs), and voice/fax/modem lines require two wires (one pair). With 4-pair wiring (8 wires) you can use all these features in the same office at the same time. (No matter how many pairs are used, this cabling is called twisted-pair wiring.) And you can have multiple connections if offices will be shared or if they will contain more than one computer or peripheral device.

Expect to spend about $100 for every cable installed, including the cost of termination, testing, and installation of the wall jacks at each end.

Tip

Standardize on wall jacks that can support all future networking types. Equipping all wall jacks with the RJ-45 connectors ensures that LocalTalk, Ethernet, Token Ring, and voice lines can all use the same jack and the same wiring. That way, to move from one protocol to another you just change the connection in the wiring closet and add a new cable from the computer to the wall jack. No new wiring or wall jacks are required.

Tip

Consider phone service when planning a network installation. Perhaps you can have network wiring installed at the same time and thereby spare some contractor costs. This also ensures that everywhere a phone connection is made a network connection is also installed, and vice versa.

Tip

Install the wiring when you move into a new building or office. That's the easiest time to do it, since there are no worries about keeping an existing network operating, and you can decide on the placement of wiring and connections as the floor plan develops. By working with designers and contractors, you can create a network wiring plan that will meet your needs for many years to come.

Tip

Most offices already have an ad hoc network, which needs to remain operational while being upgraded. The secret to dealing with this situation is to upgrade the network wiring slowly, one section (20 to 30 Macs) at a time.

If the Macs are connected via existing phone wiring, you can put new wiring in place without disturbing the current network. After the new network wiring is in place and has been tested, one evening or weekend is usually enough time to reconnect the Macs and confirm that everything is working properly.

How do you know the new network is working properly? First, have the wiring contractor check the wiring for electrical continuity and other errors to ensure that no damage occurred during installation. Then, using a portable Mac, if you have one, test each connection to confirm that all file servers and printers can be recognized and accessed (see "Testing Nodes"). Also, print a test page (from any node) to each printer to ensure that printing is also working.

2. Choose a Topology

The wires for each daisy-chained branch in a typical large LocalTalk network all converge in a central wiring closet. They are connected to each other, forming a passive star network topology (networking parlance for the network's layout).

Problem

The electrical signals that travel from one machine to another over the network can go only so far along a wire before fading out. The more wiring you have, the farther the electrical signals must travel; a signal on a passive star must travel through the entire network to get to its intended destination. A network can quickly grow to be so large that it exceeds the severe wire-length limitations of LocalTalk. Length limits depend on wire thickness; common limits are 4500 feet for 22-gauge wire, 3000 feet for 24-gauge wire, and 1800 feet for 26-gauge wire. (The higher the gauge number, the thinner the wire; and the thinner the wire, the greater its resistance.)

Solution

One way to overcome wire-length limits is to install a LocalTalk repeater, such as Farallon's PhoneNet StarController; repeaters typically cost about $1300. These repeaters amplify the LocalTalk signals so they can travel much longer distances. Repeaters also provide some management tools that can, for example, automatically remove a malfunctioning machine from the network and track network traffic (see "Monitoring Traffic"). You place repeaters where all network lines terminate, in the wiring closet. Doing so turns the network into an active star, in which a repeater actively amplifies the signals to ensure that they reach every machine on the network.

Manufacturers say that each repeater can support 10 network devices, printers, or Macs. But judging by my experience, you can connect as many as 30 devices to each repeater before problems arise.

Problem

Eventually, even an active star topology also proves insufficient for large or complex networks, particularly those that go between floors or buildings. One of the first symptoms of an overloaded network is slow printing. Repeaters can also begin showing high error rates on their status panels or in their monitoring software's log files. In a severely overloaded network, shared devices--such as printers and servers--will begin disappearing from the Chooser listing (see "Now You See It.").

Solution

An over-loaded LocalTalk network requires the next big step in expanding a network: the use of routers and a high-speed backbone to separate the traffic on the network so it is more manageable.

3. Move Past LocalTalk

As the number of Macs on a network increases, users require more services, such as electronic mail, online calendars, and file sharing. Most of those services recommend or require the installation of a dedicated file server to store all necessary data centrally.

Problem

The inclusion of a file server, the use of System 7's file sharing, and the sheer size of the network eventually slows down an AppleTalk network. The reason? Too much traffic is being sent over the network through the slow AppleTalk protocols, causing the common symptoms of an overloaded network: increased errors, disappearing services, and slow printing speeds.

Solution

Upgrade to the next network level: Ethernet, a high-speed data-linking protocol that transfers data at 10 Mbps. (LocalTalk transfers data at 230 Kbps, or about 1/40 the speed of Ethernet.) To connect Macs via Ethernet, you need an Ethernet board or external Ethernet box (either of which costs $200 to $300) on each Mac. While Quadras offer built-in Ethernet (thus needing no board), they do require a $175 transceiver.

Tip

Not everyone on the network needs to be connected via Ethernet--you can still connect many Macs via LocalTalk. All users could connect directly to the high-speed network using Ethernet boards (or the built-in Ethernet in the Quadras), or all users could connect to members of their own group via LocalTalk and the groups could connect to each other over an Ethernet backbone--essentially a mininetwork that connects network branches. You can also mix these two approaches so that, for example, graphic artists are linked directly to each other via Ethernet so they can send huge files of scanned images and page layouts relatively quickly, while accountants and administrative personnel are linked via LocalTalk, since their spreadsheet and text files are typically not large.

To connect LocalTalk-based groups to other LocalTalk-based groups via an Ethernet backbone, all you need is a LocalTalk-to-Ethernet router such as Shiva Corporation's $1999 FastPath/5 and the high-speed wiring you have already installed. A router lets LocalTalk protocols pass from the strictly LocalTalk environment of the original network to the Ethernet environment of the backbone and back again.

Tip

Similarly, attaching high-volume servers directly to a backbone lets you separate the majority of heavy traffic from the day-to-day traffic, which remains on the LocalTalk side of the router.

4. Add a Server

Servers are computers that typically have high storage capacity so you can put common data--whether files or applications--in one place for everyone to access. Servers can also make electronic mail and printing more efficient; for example, sending all print jobs to a print server keeps the user's Mac from being tied up in processing the file or waiting for a printer to be ready--the server does all the waiting.

Tip

For more moderate server needs, you can enable users to share files among themselves by using file sharing, which comes bundled with System 7. File sharing lets you make any or all of the folders on a Macintosh's hard drive accessible to other users on the network. File-sharing options let you add password protection and determine which groups of users have which types of access (such as read/write or read-only) to shared data. Such a collection of Macs is called a distributed server.

Problem

When your network requires major services like electronic mail, you will want to dedicate a Mac to providing that service. While it could run on a user's Mac, the service would slow down that Mac, and the mail system would be unavailable during any restarts and whenever that user turned off the Mac.

Solution

To avoid this problem, dedicate one Mac to be an AppleShare server. Dedicated servers make the most sense for storing large files such as color scans and customer databases, since these require more processing power than any user can spare and still use his or her Mac. If you decide to use an existing Mac as a distributed server, expect significant slowdown when other nodes access large files or applications.

Tip

While any type of Mac can work as a file server, it is best to use the fastest machine possible--a Mac IIci at the least (you don't want the server to be a speed bottleneck). Make sure any high-volume servers are connected to frequent users via a high-speed connection like Ethernet. (This prevents another bottleneck.)

Tip

One way to reduce costs is to not purchase a monitor or keyboard for the server--they will rarely be used. Instead, borrow a keyboard and monitor from another machine to set up the server, and from then on use Farallon's Timbuktu ($199) to operate the server from another Mac or even a Windows PC.

Tip

Large networks (more than 100 nodes) or high-volume servers should use a network operating system like NetWare (which costs $12,495 for a 250-user license, including NetWare for Macintosh software) from Novell (801/429-5540). While AppleShare requires only a Macintosh on either LocalTalk or Ethernet, NetWare requires one DOS-based system for the server and another DOS system for configuration and management. This second DOS machine runs Novell utilities that configure and manage the server. Client software that lets both DOS PCs and Macs talk to the server is included with NetWare.

For the NetWare server, you should use a machine based on the Intel 80386 or 80486 processor, because of its processing power. An inexpensive 80286-based DOS PC is usually fine for the NetWare manager. Together, the two DOS PCs cost about $3000, plus the cost of the high-capacity storage (perhaps $800 to $2000) you should have on the NetWare server.

5. Standardize Node Names

A well-designed network includes some planning for standard Macintosh, zone, printer, and server names. Names like Mac-n-stein are cute, but they tell very little about the owner of the Mac or its location.

Tip

You create zones when you divide a network into different segments, usually through the use of a LocalTalk-to-Ethernet router. The names of the zones should reflect this segmentation--typically by including the building names, locations, or departments that are attached to that network segment. Users are usually most comfortable with geographical or department names that provide them with some indication of how the network is divided.

Tip

Printer names should include some geographical designation such as North or East.

Tip

Because servers are usually located in one central area, geographic clues are not needed, so their names can be more friendly. Some companies name them after cartoon characters or personalities from popular fiction. You can have fun with server names, but make sure they bear some relation to the services they provide--for example, Balance Sheet for the financial users' server and Post Office for an electronic-mail server.

Tip

Changing zone names is easy, but doing so can cause users difficulties: automatic log-ons, mail programs, and printer selections, for example, might be disabled when a zone or server name changes.

Tip

Plan your naming structure to accommodate growth and minimize renaming later. When names do change, make sure that users are informed of how to recover and reset the services they use, like electronic-mail and file-server connections. Although this doesn't usually require reinstalling the products, the setup of both hardware and software often must be altered to point to the newly renamed servers or zones.

Strategies for Growth

With networks, as in many other endeavors, planning is the secret of success. Whether you are installing a new network in new offices or upgrading an existing one, planning goes a long way toward making the installation cheaper and better while disrupting current work as little as possible.

Allow as much time as possible for configuring and testing the various components. Put together a sample network in one room and test it with current software and any software that the company plans to use in the future to ensure that the network meets the company's needs. Also, make sure that all the pieces work together. Try attaching files to mail messages to see if they get through, and try using dedicated servers at the same time as distributed ones. This type of planning results in the best possible network for both the users and the company.

Douglas E. Welch is a free-lance writer and a microcomputer analyst for a major entertainment corporation in Southern California.


Sidebar

Testing Nodes

A program like Apple's InterPoll lets you monitor the network's status by sending test data to a device on the network and tracking whether it arrives. A properly functioning network (left) shows no lost packets (at the Packets Sent section of the screen) and lists the status of the target device (at the Status section). An improperly functioning network (right) shows lost packets and does not list the target device's status. Send test packets to each device to see if there are any trouble spots at a particular device or a particular section of the network.

Now You See It

A network whose size exceeds its wiring capacity often begins intermittently dropping devices and zones from the Chooser's AppleTalk zone and device lists. At left, the screen shows the full network; at right, the screen shows the same network after some zones and devices have disappeared. This symptom indicates it's time to change topologies, such as from passive star to active star, or to add routers and a backbone.

Monitoring Traffic

Star controllers, such as those from Farallon Computing, come with software to monitor the controller's ports. The screen at left shows a report on network traffic; here, traffic is light for all ports, and there have been no errors. The screen at right shows the details for one port.


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