Apple Computers' workstations have always been known for their ease of use. The products have always been geared toward simplicity for the end user. Apple extended this philosophy to networking.

All Apple computers ship with a network interface. The initial products shipped with a proprietary-networking scheme called Local Talk. However,since the early 1990's the standard physical and data link interface has been Ethernet.

Apple's early commitment to networking is one of the characteristics that made their products popular for small workgroup applications. Consequently you will still find many Macintosh computers in the work place. This is particularly true in healthcare, education, and the graphics industry.

Local Talk uses a media access technique that is similar to Ethernet. While Ethernet uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD), Local Talk uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The data transmission rate for Local Talk is 230.4 Kbps, which may seem slow today, but when you consider that non-technical users could network their machines by simply "plugging them in". In many respects Apple was way ahead of its competitors.

The Apple Talk protocol suite was introduced in the mid 1980's, which is the same period of time that the industry was focusing on (and debating about) the need for standards. Apple was one of the early adopters of the OSI reference model.

The following is a brief overview of the Apple Talk protocol stack. You do not have to memorize this, but you should be aware of it. It is not uncommon to find modern networks that are still routing Apple Talk traffic.

Apple Talk Filing Protocol (AFP) - permits users to share data files and applications on a shared server. This could be an AppleShare server, or any NOS file server application that is compatible with the Apple Talk protocols.

PostScript Protocol - provides a standard way of describing graphics and text data for printers that understand this protocol, in particular the Apple LaserWriter.

The next four protocols are responsible for insuring the end to end deliver of data, since the lower layers of the Apple Talk stack operate on a "best effort" basis:

ASP - AppleTalk Session Protocol

PAP - Printer Access Protocol

ATP - AppleTalk Transaction Protocol

ADSP - AppleTalk Data Stream Protocol

RTMP - Routing Table Maintenance Protocol maintains a data table that facilitates routing datagrams through router ports to other networks. It permits routers to dynamically learn routes to other AppleTalk networks in an Internet.

AEP - Apple Talk Echo Protocol permits a node to send a datagram to another node and receive a copy, or "echo," of the transmitted datagram. This is used to determine whether another node is reachable and also the delay between the two nodes.

NBP - Name Binding Protocol is used for assigning names to printers.

DDP - Datagram Delivery Protocol uses RTMP and AEP as tools to devliver data across the network. DDP exchanges data packets called datagrams. The DDP permits running AppleTalk as a process-to-process, best-effort delivery system, in which the processes running in the nodes of an interconnected network can exchange packets with each other. (A process can be thought of as a program or program segment.) As mentioned above, higher layer protocols ensure that data is actually delivered. A key point about DDP is that it is a routable protocol.

Apple Talk supports various datalink protocols based on the network scheme that you are employing. For example if your network were Ethernet, then an Apple workstation or server would use the Ether Talk Link Access Procedure (ELAP). I have only shown three protocols in the table, however there are other protocols that were used to support older networking schemes, ArcNet being an example.

LLAP - Local Talk Link Access Protocol

ELAP - Ether Talk Link Access Protocol

TLAP - Token Talk Link Access Protocol

Physical Layer Connections - Physical layer connections are again based on the media access scheme employed. Local Talk, Ethernet and Token Ring are shown in the table.