AppleTalk
AppleTalk is a discontinued proprietary suite of networking protocols developed by Apple Computer for their Macintosh computers. AppleTalk includes a number of features that allow local area networks to be connected with no prior setup or the need for a centralized router or server of any sort. Connected AppleTalk-equipped systems automatically assign addresses, update the distributed namespace, and configure any required inter-networking routing.
AppleTalk was released in 1985 and was the primary protocol used by Apple devices through the 1980s and 1990s. Versions were also released for the IBM PC and compatibles and the Apple IIGS. AppleTalk support was also available in most networked printers, some file servers, and a number of routers.
The rise of TCP/IP during the 1990s led to a reimplementation of most of these types of support on that protocol, and AppleTalk became unsupported as of the release of Mac OS X v10.6 in 2009. Many of AppleTalk's more advanced autoconfiguration features have since been introduced in Bonjour, while Universal Plug and Play serves similar needs.
History
AppleNet
After the release of the Apple Lisa computer in January 1983, Apple invested considerable effort in the development of a local area networking system for the machines. Known as AppleNet, it was based on the seminal Xerox XNS protocol stack but running on a custom coaxial cable system rather than Xerox's Ethernet. AppleNet was announced early in 1983 with a full introduction at the target price of $500 for plug-in AppleNet cards for the Lisa and the Apple II.At that time, early LAN systems were just coming to market, including Ethernet, Token Ring, Econet, and ARCNET. This was a topic of major commercial effort at the time, dominating shows like the National Computer Conference in Anaheim in May 1983. All of the systems were jockeying for position in the market, but even at this time, Ethernet's widespread acceptance suggested it was to become a de facto standard. It was at this show that Steve Jobs asked Gursharan Sidhu a seemingly innocuous question: "Why has networking not caught on?"
Four months later, in October, AppleNet was cancelled. At the time, they announced that "Apple realized that it's not in the business to create a networking system. We built and used AppleNet in-house, but we realized that if we had shipped it, we would have seen new standards coming up." In January, Jobs announced that they would instead be supporting IBM's Token Ring, which he expected to come out in a "few months".
AppleBus
Through this period, Apple was deep in development of the Macintosh computer. During development, engineers had made the decision to use the Zilog 8530 serial controller chip instead of the lower-cost and more common UART to provide serial port connections. The SCC cost about $5 more than a UART, but offered much higher speeds of up to 250 kilobits per second and internally supported a number of basic networking-like protocols like IBM's Bisync.The SCC was chosen because it would allow multiple devices to be attached to the port. Peripherals equipped with similar SCCs could communicate using the built-in protocols, interleaving their data with other peripherals on the same bus. This would eliminate the need for more ports on the back of the machine, and allowed for the elimination of expansion slots for supporting more complex devices. The initial concept was known as AppleBus, envisioning a system controlled by the host Macintosh polling "dumb" devices in a fashion similar to the modern Universal Serial Bus.
AppleBus networking
The Macintosh team had already begun work on what would become the LaserWriter and had considered a number of other options to answer the question of how to share these expensive machines and other resources. A series of memos from Bob Belleville clarified these concepts, outlining the Mac, LaserWriter, and a file server system which would become the Macintosh Office. By late 1983 it was clear that IBM's Token Ring would not be ready in time for the launch of the Mac, and might miss the launch of these other products as well. In the end, Token Ring would not ship until October 1985.Jobs' earlier question to Sidhu had already sparked a number of ideas. When AppleNet was cancelled in October, Sidhu led an effort to develop a new networking system based on the AppleBus hardware. This new system would not have to conform to any existing preconceptions, and was designed to be worthy of the Mac – a system that was user-installable and required no configuration or fixed network addresses – in short, a true plug-and-play network. Considerable effort was needed, but by the time the Mac was released, the basic concepts had been outlined, and some of the low-level protocols were on their way to completion. Sidhu mentioned the work to Belleville only two hours after the Mac was announced.
The "new" AppleBus was announced in early 1984, allowing direct connection from the Mac or Lisa through a small box that is plugged into the serial port and connected via cables to the next computer upstream and downstream. Adaptors for Apple II and Apple III were also announced. Apple also announced that an AppleBus network could be attached to, and would appear to be a single node within, a Token Ring system. Details of how this would work were sketchy.
AppleTalk Personal Network
Just prior to its release in early 1985, AppleBus was renamed AppleTalk. Initially marketed as AppleTalk Personal Network, it comprised a family of network protocols and a physical layer.The physical layer had a number of limitations, including a speed of only, a maximum distance of from end to end, and only 32 nodes per LAN. But as the basic hardware was built into the Mac, adding nodes only cost about $50 for the adaptor box. In comparison, Ethernet or Token Ring cards cost hundreds or thousands of dollars. Additionally, the entire networking stack required only about 6 kB of RAM, allowing it to run on any Mac.
The relatively slow speed of AppleTalk allowed further reductions in cost. Instead of using RS-422's balanced transmit and receive circuits, the AppleTalk cabling used a single common electrical ground, which limited speeds to about, but allowed one conductor to be removed. This meant that common three-conductor cables could be used for wiring. Additionally, the adaptors were designed to be "self-terminating", meaning that nodes at the end of the network could simply leave their last connector unconnected. There was no need for the wires to be connected back together into a loop, nor the need for hubs or other devices.
The system was designed for future expansion; the addressing system allowed for expansion to 255 nodes in a LAN, and by using "bridges" one could interconnect LANs into larger collections. "Zones" allowed devices to be addressed within a bridge-connected internet. Additionally, AppleTalk was designed from the start to allow use with any potential underlying physical link, and within a few years, the physical layer would be renamed LocalTalk, so as to differentiate it from the AppleTalk protocols.
One advantage of AppleTalk was that it was auto-configuring. To join a device to a network, a user simply plugged the adaptor into the machine, then connected a cable from it to any free port on any other adaptor. The AppleTalk network stack negotiated a network address, and compiled a list of names and types of other machines on the network so the user could browse the devices through the Chooser. AppleTalk was so easy to use that ad hoc networks tended to appear whenever multiple Macs were in the same room. Apple would later use this in an advertisement showing a network being created between two seats in an airplane. A disadvantage of AppleTalk Personal Network is that cable connectors easily separate, causing network failures.
PhoneNet and other adaptors
Slow but inexpensive, AppleTalk became widely popular. A thriving third-party market for AppleTalk devices developed over the next few years. One particularly notable example was an alternate adaptor designed by BMUG and commercialised by Farallon as PhoneNET in 1987. This was essentially a replacement for Apple's connector using conventional phone jacks instead of Apple's round connectors. PhoneNet allows AppleTalk networks to be connected together using normal telephone wires, and with very little extra work, can run analog phones and AppleTalk on a single four-conductor phone cable.Other companies took advantage of the SCC's ability to read external clocks in order to support higher transmission speeds, up to. In these systems, the external adaptor also included its own clock, and used that to signal the SCC's clock input pins. The best-known such system was Centram's FlashTalk, which ran at, and was intended to be used with their TOPS networking system. A similar solution was the DaynaTalk, which used a separate box that plugged in between the computer and a normal LocalTalk/PhoneNet box. Dayna also offered a PC expansion card that ran up to when talking to other Dayna PC cards. Several other systems also existed with even higher performance, but these often required special cabling that was incompatible with LocalTalk/PhoneNet, and also required patches to the networking stack that often caused problems.