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AppleTalk across Penn: Making the most of Apple's built in networking protocol

By Bill Rawles

AppleTalk is the built-in, proprietary protocol Macintosh computers use to communicate with each other and with peripheral devices, such as file servers and printers. Originally conceived as a local area network (LAN) scheme, AppleTalk takes on new significance in a campus-wide networking environment. Via PennNet, Mac users can share files and printers throughout the University (subject to password and courtesy restrictions, of course).

Changes made in August make campus-wide AppleTalk easier to use, easier to administer, and faster. (See the sidebar below for technical details.) The most visible change is a change in zone naming conventions. All networked Macintoshes and AppleTalk peripherals are grouped in zones, which appear in the Chooser. All zone names now follow a tiered structure. Each name begins with UPenn, followed by short forms of the major organization entity (e.g., SAS), and the department, separated by periods. This naming structure aids in finding a specific zone by grouping each organization's zones and by alphabetizing the major organizations and the zones within them.

What you can do with it

Some specific examples for faculty, staff, and students in ResNet rooms include:

Faculty

• You can set up a modem connection to the Macintosh in your campus office and, using AppleTalk Remote Access Protocol (ARAP), dial in from home and work as though you were directly connected to PennNet with all the resources you normally use readily available.
• If you have two offices with Macintoshes in each and you sometimes need to use data from one on the other, you can set up your Macs so that you can retrieve that data anytime.
• If you have assigned a research report that you want submitted on paper, you can make your printer available to your students and have them print their papers directly to it.

• If you have a printer you want to share with coworkers, simply define it to your AppleTalk zone and let people know where it is available. Use a descriptive name for your printer; now that users all over campus can see printers, default names like "Laser Writer II" do not provide adequate identification. "VPUL LW in FB210" lets people be confident they're printing to the correct device.
• If you have a newsletter article draft that needs to be reviewed and marked up by the editor, you can print it to her printer from any office on campus.
• If you want to share specific files with another person or group, you can (assuming you are using System 7) use built-in personal AppleShare to give them access.
• If your office is relocated for renovation, you can still use the department file server as the default server for your work, regardless of your new location and the intervening distance.

• If you have a printer you want to share with friends, simply define it to your AppleTalk zone and let people know where it is available. Use a descriptive name for your printer; now that users all over campus can see printers, default names like "Laser Writer II" do not provide adequate identification. "Joe'sLW in HRN 1310" lets people be confident they're printing to the correct device.
• Where available, you can access AppleShare file servers in campus computer labs to do homework assignments without leaving your dorm room (check with your particular school to find out if this applies to you).
• Should you forget a file you need to use in a computer lab, you can simply retrieve it electronically if you have configured the Mac in your room for personal AppleShare.

How you do it

• From the Apple menu select Control Panels.
• Double-click on the Network icon.
• In the Network control panel click on the EtherTalk icon.
• From the list of zones displayed (only zones in your subnetwork will be displayed here) select the zone you want to be your default.

Different levels of access control and security can be established for your own printers and servers depending on your needs.

Sidebar: Apple (Tech) Talk

PennNet and the overall amount of network traffic have grown significantly in recent years. To improve network reliability and performance, the Office of Data Communications and Computing Services found it necessary to segment PennNet into subnetworks. The only protocol used to communicate from one subnetwork to another was IP, the protocol used on the worldwide Internet. A protocol is a set of rules defining how networked devices communicate with each other.

PennNet's growth was paralleled by the growth on campus of networks based on the AppleTalk protocol. AppleTalk is the second major network transport protocol to become supported for campus-wide data communications at Penn. During the past two years, more and more organizations have needed the ability to communicate using AppleTalk across subnetworks. Until last August, the only way to do this was by tunneling.

Tunneling means sending AppleTalk data to a device that wraps or "encapsulates" it in IP packets and then sends it across subnetworks. When it reaches its destination subnetwork, a corresponding device is required to take AppleTalk out of IP and send it to the appropriate Macintosh or peripheral. Tunneling requires the purchase, installation, configuration, and management of special routers in any subnetwork where AppleTalk is used and must be sent to other subnetworks. Tunneling was practical when there were very few groups who needed this capability and few subnets were affected. As the number of groups grew, and the number of subnets to be spanned increased, tunneling became an expensive network management burden.

On August 20, Data Communications and Computing Services, with the assistance of AppleTalk network administrators across campus and Apple Computer, Inc. engineers, converted AppleTalk from a tunneled to a routed protocol. AppleTalk data is now routed directly by PennNet equipment.

Be prepared

Why do all the AppleTalk zone names that appear in your Chooser begin with UPenn? As networking technology has developed, some institutions have experimented with exchanging AppleTalk data across the Internet. These trials revealed many zone name conflicts among institutions. One way to avoid this problem is to use an institutional identifier--much like Internet addresses use. For us, that's UPenn.

AppleTalk across the Internet is not available at Penn now. Anticipating future developments, however, the AppleTalk community at Penn has chosen zone naming conventions that will prepare us to participate in a broader world of multiple-protocol communications.