October 1993 - Volume 10:2
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 itUbiquitous AppleTalk allows for dynamic file and print sharing. You can connect to any campus zone and change zones as needed. There are no on-campus geographic restrictions, so you can share files and printers with any cooperative partner anywhere on campus.
Some specific examples for faculty, staff, and students in ResNet rooms include:
How you do itWhen you select the Chooser from the Apple menu, you will notice that there are many AppleTalk zones, including a large number of default zones. When you first connect your Mac to Ethernet you will be in the ".default" zone for your PennNet "subnetwork." You can select which of your organization's zones your Mac will appear in when you start it each day. To do this:
You can, through your Chooser, select any file server or printer as your default. Remember, however, that it is bad net etiquette--at a minimum--to use other's printers or servers without permission. Gaining access to servers or printers that you are not explicitly authorized to access violates University policies and may even break some state or federal laws. The best guideline is if you don't have explicit permission, don't use it. (See the University's new Policy on Ethical Behavior with Respect to the Electronic Information Environment, promulgated by the Office of the President and published in the September 1993 Penn Printout.)
Different levels of access control and security can be established for your own printers and servers depending on your needs.
BILL RAWLES is a Program Manager for Network Services and Programs at the Office of Data Communications and Computing Services.
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.
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.