AppleTalk

AppleTalk protocol layers in relation to the OSI computer communication model.

Appletalk is a set of protocols developed by Apple Inc. for the interconnection of local networks. It was shipped on an Apple Macintosh in 1984 and is currently deprecated on Macintoshes in favor of TCP/IP networks.

History

• 1984: Development and inclusion in a Macintosh
• 1985: At that time only printers were shared using the Selector or Chooser concept.
• 1986: The routers are introduced, their function is to separate networks into small portions to avoid saturation and traffic.
• 1987: EtherTalk and a file server are introduced. Until this year, files are shared and a server is as such.
• 1988: VAXes and PCs are introduced to the network. At this time the first connections of Macintosh are given with other environments.
• 1989: There are already thousands of EtherTalk nodes. The first interconnections are introduced to Internet networks.

Phases

We can divide Appletalk into two phases in terms of its features:

Phase 1 (1985)

• Speed of 230.4kbit/s.
• Maximum distance of 305 meters.
• 32 maximum nodes per LAN network.

Phase 2 (1989)

• Network organization in areas.
• More than 255 nodes per LAN network.
• Introduction of EtherTalk, TokenTalk and LocalTalk for IBM PC.
• The appearance of a simpler to use connector (AppleAUI).

Versions

• For IBM PC and compatible.
• For Apple IIGS.

Available for most:

• Network printers (especially in laser printers).
• Some file servers.
• A certain series of routers.

Design

Appletalk's design is based on the OSI model but unlike other LAN systems it was not built on the Xerox XNS system, it did not have Ethernet and it did not have 48-bit addresses for routing.

Addressing

This protocol included a series of features that allowed local networks to connect without prior configuration or the need for a router or server. Appletalk is equipped to assign addresses and configure any routing automatically.

Protocols

Appletalk protocols in the OSI model

Level 1

• LocalTalk → It is based on a braided pair cable system and a transceiver running at a speed of 230.4 kbit/s.
• Ethernet → Network connection standard that uses a physical card.
• Token Ring → Network architecture with physical topology in ring.
• FDDI → Data interface distributed by fiber.

Level 2

• AARP (AppleTalk Address Resolution Protocol) → A package is issued asking for a network address (which needs the device to connect), until there is an address that does not have any equipment, when it is found it will be used for the team.

Level 3

• DDP (Datagram Delivery Protocol) → Carry out low-level data transport.

Level 4

• ATP (AppleTalk Transaction Protocol) → Read the request and return an answer.
• AEP (AppleTalk Echo Protocol) → Generates packages that are sent to the node, the package is copied, and a field in the package is altered to create a response package, which is returned to the node of origin (the one that generated the first message).
• NBP (Name Binding Protocol) → It is registered under a name. In case you want a service, NBP consults to find that service.
• RTMP (Routing Table Maintenance Protocol) → The routers keep each other informed at all times about the topology of the network.

Level 5

• ZIP (Zone Information Protocol) → Partners Appletalk network numbers with zone names.
• ASP (AppleTalk Session Protocol) → Request answers to orders, and conducts state out-of-band queries.
• ADSP (AppleTalk Data Stream Protocol) → Connection attempt can be rejected. Once the connection of one of the parts is cut, it will be closed.

Level 6 and 7

• AFP (Apple Filling Protocol) → It communicates with AppleShare file servers.
• PAP (Printer Access Protocol) → Allows communication with PostScrip printers.

Hardware

The initial default hardware for Appletalk was a high-speed protocol known as LocalTalk that used the Macintosh's RS-422 ports at 230.4 kbit/s. LocalTalk split the RS-422 port to provide uplink and downlink cable on a single port. The system would be slow these days, but thanks to its cost/complexity ratio, Macs used to be the only networked machines in many businesses.

A common replacement for LocalTalk was PhoneNet, an alternative solution (from a company called Farallon) that also used the RS-422 port and was less expensive to install and maintain. Ethernet and token ring were also used, known as EtherTalk and TokenTalk respectively. EtherTalk gradually became the dominant method for Appletalk as Ethernet caught on in the PC industry through the 1990s.