AppleTalk is a suite of network protocols introduced by Apple Computer in 1985.
AppleTalk is Apple’s proprietary protocol suite for Macintosh network communications. It provides a multilayer, peer-to-peer architecture that uses services built into the operating system. This gives every Macintosh networking capabilities. AppleTalk can run under any of several network operating systems, including Apple’s AppleShare, Novell’s NetWare for Macintosh, and Sun Microsystems’ TOPS. AppleTalk was developed in the mid-1980s with the goal of providing a simple, portable, easy-to-use, and open networking environment. To access such a network, a user just needs to “plug in, log in, and join in.” A newer version, Phase 2, was released in 1989. This version provided some new capabilities and extended others.
All AppleTalk networks use the DDP (Datagram Delivery Protocol) at the network layer, regardless of the architecture operating at the data-link layer. This protocol makes a best effort at packet delivery, but delivery is not guaranteed. Note also the AARP (AppleTalk Address Resolution Protocol) at this layer. The AARP maps AppleTalk (network) addresses to Ethernet or Token Ring (physical) addresses.
For reliable packet delivery, the ADSP (AppleTalk Data Stream Protocol) and ATP (AppleTalk Transaction Protocol) are available. Each of these protocols is appropriate under different conditions. The NBP (Name Binding Protocol) and ZIP (Zone Information Protocol) help make addressing easier. NBP associates easy-to-remember names (used by users) with the appropriate address. ZIP is used mainly on larger networks or internetworks, which are more likely to be divided into zones. A zone is a logical grouping of nodes that together make up a subnetwork. The concept of a zone was introduced to allow for larger networks with more than 255 nodes, and also to make addressing and routing tasks easier. Applications access an AppleTalk network through the AFP (AppleTalk Filing Protocol); they access printer services by shipping PostScript files through the PAP (Printer Access Protocol). A few protocols make use of services from more than one lower-level protocol. For example, ZIP relies on ATP and DDP services.