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AppleTalk is a set of local area network communication protocols originally created for Apple computers.
A D V E R T I S E M E N T
An AppleTalk network can support up to 32 devices and data can be exchanged at a speed of 230.4 kilobits per second (Kbps). Devices can be as much as 1,000 feet apart. AppleTalk's Datagram Delivery Protocol corresponds closely to the Network layer of the Open Systems Interconnection (OSI) communication model.
AppleTalk, a protocol suite developed by Apple Computer in the early 1980s, was developed in conjunction with the Macintosh computer. AppleTalk's purpose was to allow multiple users to share resources, such as files and printers. The devices that supply these resources are called servers, while the devices that make use of these resources (such as a user's Macintosh computer) are referred to as clients. Hence, AppleTalk is one of the early implementations of a distributed client/server networking system. This chapter provides a summary of AppleTalk's network architecture.
AppleTalk Phase 1, which is the first AppleTalk specification, was developed in the early 1980s strictly for use in local workgroups. Phase 1 therefore has two key limitations: Its network segments can contain no more than 135 hosts and 135 servers, and it can support only nonextended networks. Extended and nonextended networks will be discussed in detail later in the sections "Extended Networks" and "Nonextended Networks."
Addressing
Addressing is dynamic with each computer, when powered on, choosing its last
used address or a random address. The computer broadcasts that address to
determine if the address is used. If it is used, it will broadcast another
random address until it finds an unused address.
EtherTalk and TokenTalk provide for use of AppleTalk network protocols on top
of ethernet and token ring architectures respectively.
LocalTalk
LocalTalk uses STP cable and bus topology. Using CSMA/CA for media access,
computers will first determine if any other computers are transmitting, before
they transmit. A packet is transmitted prior to transmitting that alerts other
computers that a transmission will be sent. Usually LocalTalk is only used in
small environments.
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