AppleTalk is a multi-layered protocol of Apple Computers providing internetwork routing, transaction and data stream service, naming service, and comprehensive file and print sharing among Apple systems using the LocalTalk interface built into the Appl hardware. AppleTalk ports to other network media such as Ethernet by the use of LocalTalk to Ethernet bridges or by Ethernet add-in boards for Apple machines. Many third-party applications exist for the AppleTalk protocols.

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. At the physical level, AppleTalk is a network with a bus topology that uses a trunk cable between connection modules.

The LocalTalk Link Access Protocol (LLAP) must be common to all systems on the network bus and handles the node-to-node delivery of data between devices connected to a single AppleTalk network. Data link layer interfaces to Ethernet, Token ring and FDDI are defined.

The Datagram Delivery Protocol (DDP) is the AppleTalk protocol implemented at the network layer. DDP is a connectionless datagram protocol providing best-effort delivery, which is similar to IP in the TCP/IP suite.

At the Transport Layer, several protocols exist to add different types of functionality to the underlying services. The Routing Table Maintenance Protocol (RTMP) allows bridges and internet routers to dynamically discover routes to the different AppleTalk networks in an internet. The AppleTalk Transaction Protocol (ATP) is responsible for controlling the transactions between requestor and responder sockets.

The Name Binding Protocol (NBP) is for the translation of a character string name into the internet address of the corresponding client. The AppleTalk Echo Protocol (AEP) allows a node to send data to any other node on an AppleTalk internet and receive an echoed copy of that data in return. The AppleTalk Data Stream Protocol (ADSP) is designed to provide byte-stream data transmission in a full duplex mode between any two sockets on an AppleTalk internet. The Zone Information Protocol (ZIP) is used to maintain an internet-wide mapping of networks to zone names.

In the Session Layer, the AppleTalk Session Protocol (ASP) is designed to interact with AppleTalk Transaction Protocol (ATP) to provide for establishing, maintaining and closing sessions.

The AppleTalk Filing Protocol (AFP) is an application or presentation layer protocol designed to control access to remote file systems. A key application using this protocol is the AppleShare for file sharing among a variety of user computers.

Protocol Structure

AppleTalk protocols in the OSI layers:

AppleTalk protocols in the OSI layers

Related protocols: Ethernet, Token Ring, FDDI

Sponsor Source: AplleTalk protocols are defined by Apple Computer.

Reference: http://developer.apple.com/macos/opentransport/docs/dev/Inside_AppleTalk.pdf: Inside AppleTalk http://developer.apple.com/macos/opentransport/docs/dev/Inside_AppleTalk.pdf: Inside AppleTalk