AppleTalk is a proprietary suite of protocols developed by Apple Inc for computer networking. It was included in the original Macintosh (1984) and is now deprecated by Apple in favor of TCP/IP networking. It has been suggested that this article or section be merged with communications protocol. ... Apple Inc. ... Computer networks may be classified according to the network layer at which they operate according to some basic reference models that are considered to be standards in the industry such as the seven layer OSI reference model and the four layer Internet Protocol Suite model. ... This article is about the year. ... The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. ...

Design

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The AppleTalk design rigorously followed the OSI model of protocol layering. Unlike most other early LAN systems, AppleTalk was not built on the archetypal Xerox XNS system, as the intended target was not Ethernet and did not have 48-bit addresses to route. Nevertheless many portions of the AppleTalk system have direct analogs in XNS. Image File history File links Question_book-3. ... Image File history File links Acap. ... The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection (OSI) initiative. ... “LAN” redirects here. ... Xerox network services (XNS) is a protocol stack which provided routing and packet delivery developed by Xerox at Xerox PARC in the later 1970s and early 1980s. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ...

One key differentiator for AppleTalk was that the system contained three protocols aimed at making the system completely self-configuring. The AppleTalk address resolution protocol (AARP) allowed AppleTalk hosts to automatically generate their own network addresses, and the Name Binding Protocol (NBP) was essentially a dynamic Domain Name System (DNS) system which mapped network addresses to user-readable names. Although systems similar to AARP existed in other systems, Banyan VINES for instance, nothing like NBP has existed until recently. It has been suggested that this article be split into multiple articles. ... Banyan VINES (for Virtual Integrated NEtwork Service) is a computer network operating system and the set of computer network protocols it uses to talk to client machines on the network. ...

Both AARP and NBP had defined ways to allow "controller" devices to override the default mechanisms. The concept here was to allow routers to provide all of this information, or additionally "hardware" the system to known addresses and names. On larger networks where AARP could cause problems as new nodes searched for free addresses, the addition of a router could dramatically reduce "chattiness."

Together AARP and NBP made AppleTalk an easy-to-use networking system (according to some, possibly the easiest yet developed). New machines were added to the network simply by plugging them in, and optionally giving them a name. The NBP lists were examined and displayed by a program known as the Chooser (originally because it allowed you to choose your default printer) which would display a list of machines on the local network, divided into classes such as fileservers and printers. All of this was completely automated. The Chooser was an application program for Macintosh systems using the original Mac OS. The Chooser started out as a desk accessory and became a standalone application program as of System 7. ...

One problem for AppleTalk is that it was originally intended to be part of a project known as Macintosh Office, which would consist of a host machine providing routing, printer sharing and file sharing. However this project was cancelled in 1986. Despite this, the LaserWriter included built-in AppleTalk. Apple did eventually release a File and Print Server known as the AppleShare File and Print Servers. The Apple LaserWriter was one of the first laser printers available to the mass market. ...

For some the old AppleTalk protocol was considered clunky and often called 'chatty', notably on larger networks and Wide area networks (WAN) where the naming services generated considerable unwanted traffic. AppleTalk Phase 2, included with System 7, reduced the chattiness significantly. Wide Area Network (WAN) is a computer network that covers a broad area (i. ... System 7 (codenamed Big Bang) was a version of Mac OS, the operating system of the Apple Macintosh computer. ...

Today AppleTalk support is provided for backward compatibility in many products, but the default networking on the Mac is TCP/IP. Starting with Mac OS X v10.2, Bonjour (originally named Rendezvous) provides similar discovery and configuration services for TCP/IP-based networks. Bonjour is Apple's implementation of ZeroConf, which was written specifically to bring NBP's ease-of-use to the TCP/IP world. The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet and most commercial networks run. ... Mac OS X version 10. ... Bonjour, formerly Rendezvous, is Apple Inc. ... Zeroconf or Zero Configuration Networking is a set of techniques that automatically create a usable IP network without configuration or special servers. ...

Addressing

An AppleTalk address was a 4-byte quantity. This consisted of a two-byte network number, a one-byte node number, and a one-byte socket number. Of these, only the network number required any configuration, being obtained from a router. Each node dynamically chose its own node number, according to a protocol which handled contention between different nodes accidentally choosing the same number. For socket numbers, a few well-known numbers were reserved for special purposes specific to the AppleTalk protocol itself. Apart from these, all application-level protocols were expected to use dynamically-assigned socket numbers at both the client and server end.

Because of this dynamism, users could not be expected to access services by specifying their address. Instead, all services had names which, being chosen by humans, could be expected to be meaningful to users, and also could be sufficiently long enough to minimize the chance of conflicts.

Note that, because a name translated to an address, which included a socket number as well as a node number, a name in AppleTalk mapped directly to a service being provided by a machine, which was entirely separate from the name of the machine itself. Thus, services could be moved to a different machine and, so long as they kept the same service name, there was no need for users to do anything different to continue accessing the service. And the same machine could host any number of instances of services of the same type, without any network connection conflicts.

Contrast this with A records in the DNS, where a name translates only to a machine address, not including the port number that might be providing a service. Thus, if people are accustomed to using a particular machine name to access a particular service, their access will break when the service is moved to a different machine. This can be mitigated somewhat by insistence on using CNAME records indicating service rather than actual machine names to refer to the service, but there is no way of guaranteeing that users will follow such a convention. (Some newer protocols, such as Kerberos and Active Directory use DNS SRV records to identify services by name, which is much closer to the AppleTalk model.) It has been suggested that this article be split into multiple articles. ... Kerberos is the name of a computer network authentication protocol, which allows individuals communicating over an insecure network to prove their identity to one another in a secure manner. ... Typically Active Directory is managed using the graphical Microsoft Management Console. ...

Protocols

AppleTalk Address Resolution Protocol

AARP resolves AppleTalk addresses to physical layer, usually MAC, addresses. It is functionally equivalent to ARP. This article does not cite any references or sources. ... In computer networking a Media Access Control address (MAC address) or hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NICs). ... In computer networking, the Address Resolution Protocol (ARP) is the standard method for finding a hosts hardware address when only its network layer address is known. ...

AARP is a fairly simple system. When powered on, an AppleTalk machine broadcasts an AARP probe packet asking for a network address, intending to hear back from controllers such as routers. If no address is provided, one is picked at random from the "base subnet", 0. It then broadcasts another packet saying "I am selecting this address", and then waits to see if anyone else on the network complains. If another machine has that address, it will pick another address, and keep trying until it finds a free one. On a network with many machines it may take several tries before a free address is found, so for performance purposes the successful address is "written down" in NVRAM and used as the default address in the future. This means that in most real-world setups where machines are added a few at a time, only one or two tries are needed before the address effectively become constant. It has been suggested that this article or section be merged with Non-volatile memory. ...

AppleTalk Data System Protocol

This was a comparatively late addition to the AppleTalk protocol suite, done when it became clear that a TCP-style reliable connection-oriented transport was needed. Significant differences from TCP were: The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ...

• a connection attempt could be rejected
• there were no "half-open" connections; once one end initiated a tear-down of the connection, the whole connection would be closed (i.e., ADSP is full-duplex, not dual simplex).

A duplex communication system is a system composed of two connected parties or devices which can communicate with one another in both directions. ...

Apple Filing Protocol

The Apple Filing Protocol (AFP), formerly AppleTalk Filing Protocol, is the protocol for communicating with AppleShare file servers. Built on top of AppleTalk Session Protocol, it provides services for authenticating users (extensible to different authentication methods including two-way random-number exchange) and for performing operations specific to the Macintosh HFS filesystem. AFP is still in use in Mac OS X, even though most other AppleTalk protocols have been deprecated. The Apple Filing Protocol (AFP) is a layer 6 (presentation layer) network protocol that offers file services for Mac OS X and Classic Mac OS. In Mac OS X, AFP is one of several file services supported including Server Message Block (SMB), Network File System (NFS), File Transfer Protocol (FTP... The AppleShare protocol is a communications protocol from Apple Computer that allows client applications in a computer to exchange files with and request services from server programs in a computer network. ... Hierarchical File System (HFS), is a file system developed by Apple Computer for use on computers running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs. ...

AppleTalk Session Protocol

ASP was an intermediate protocol, built on top of ATP, which in turn was the foundation of AFP. It provided basic services for requesting responses to arbitrary commands and performing out-of-band status queries. It also allowed the server to send asynchronous attention messages to the client.

AppleTalk Transaction Protocol

ATP was the original reliable transport-level protocol for AppleTalk, built on top of DDP. At the time it was being developed, a full, reliable connection-oriented protocol like TCP was considered to be too expensive to implement for most of the intended uses of AppleTalk. Thus, ATP was a simple request/response exchange, with no need to set up or tear down connections.

An ATP request packet could be answered by up to eight response packets. The requestor then sent an acknowledgement packet containing a bit mask indicating which of the response packets it received, so the responder could retransmit the remainder.

ATP could operate in either "at-least-once" mode or "exactly-once" mode. Exactly-once mode was essential for operations which were not idempotent; in this mode, the responder kept a copy of the response buffers in memory until successful receipt of a release packet from the requestor, or until a timeout elapsed. This way, it could respond to duplicate requests with the same transaction ID by resending the same response data, without performing the actual operation again.** In mathematics, an idempotent element is an element which, intuitively, leaves something unchanged. ...

Datagram Delivery Protocol

DDP was the lowest-level data-link-independent transport protocol. It provided a datagram service with no guarantees of delivery. All application-level protocols, including the infrastructure protocols NBP, RTMP and ZIP, were built on top of DDP. A packet is the fundamental unit of information carriage in all modern computer networks. ...

Name Binding Protocol

NBP was a dynamic, distributed system for managing AppleTalk names. When a service started up on a machine, it registered a name for itself on that machine, as chosen by a human administrator. At this point, NBP provided a system for checking that no other machine had already registered the same name. Then later, when a client wanted to access that service, it used NBP to query machines to find that service. NBP provided browseability ("what are the names of all the services available?") as well as the ability to find a service with a particular name.

As would be expected from Apple, names were truly human readable, containing spaces, upper and lower case letters, and including support for searching.

Printer Access Protocol

PAP was the standard way of communicating with PostScript printers. It was built on top of ATP. When a PAP connection was opened, each end sent the other an ATP request which basically meant "send me more data". The client's response to the server was to send a block of PostScript code, while the server could respond with any diagnostic messages that might be generated as a result, after which another "send-more-data" request was sent. This use of ATP provided automatic flow control; each end could only send data to the other end if there was an outstanding ATP request to respond to. For the literary term, see Postscript. ... The flow control mechanism is used for controlling the flow of data in a network under well-defined conditions, while congestion control is used for controlling the flow of data when congestion has actually occurred . ...

PAP also provided for out-of-band status queries, handled by separate ATP transactions. Even while it was busy servicing a print job from one client, a PAP server could continue to respond to status requests from any number of other clients. This allowed other Macintoshes on the LAN that were waiting to print to display status messages indicating that the printer was busy, and what the job was that it was busy with.

Routing Table Maintenance Protocol

RTMP was the protocol by which routers kept each other informed about the topology of the network. This was the only part of AppleTalk that required periodic unsolicited broadcasts: every 10 seconds, each router had to send out a list of all the network numbers it knew about and how far away it thought they were.

Zone Information Protocol

ZIP was the protocol by which AppleTalk network numbers were associated with zone names. A zone was a subdivision of the network that made sense to humans (for example, "Accounting Department"); but while a network number had to be assigned to a topologically-contiguous section of the network, a zone could include several different discontiguous portions of the network.

Physical implementation

The initial default hardware implementation for AppleTalk was a high-speed serial protocol known as LocalTalk that used the Macintosh's built-in RS-422 ports at 230.4 kbit/s. LocalTalk used a splitter box in the RS-422 port to provide an upstream and downstream cable from a single port. The system was slow by today's standards, but at the time the additional cost and complexity of networking on PC machines was such that it was common that Macs were the only networked machines in the office. LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. ... The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ... EIA-422 (formerly RS-422) is a serial data communication protocol which specifies 4-wire, full-duplex, differential line, multi-drop communications. ...

Other physical implementations were also available. One common replacement for LocalTalk was PhoneNet, a 3rd party solution (from a company called Farallon) that also used the RS-422 port and was indistinguishable from LocalTalk as far as Apple's LocalTalk port drivers were concerned, but ran over two unused wires in existing phone cabling. PhoneNet was considerably less expensive to install and maintain. Ethernet and TokenRing was also supported, known as EtherTalk and TokenTalk respectively. EtherTalk in particular gradually became the dominant implementation method for AppleTalk as Ethernet became generally popular in the PC industry throughout the 1990s. PhoneNet is an implementation of the LocalTalk network physical layer created by Farallon Computing (now Netopia). ...

Networking model

The application layer is the seventh level of the seven-layer OSI model. ... The presentation layer is the sixth level of the seven layer OSI model. ... The session layer is level five of the seven level OSI model. ... AppleTalk is a proprietary suite of protocols developed by Apple Computer for computer networking. ... The Name Binding Protocol (NBP) is the AppleTalk protocol used for translating network device names to addresses. ... The network layer is third layer out of seven in OSI model and it is the third layer out of five in TCP/IP model. ... Datagram Delivery Protocol (DDP) is a member of the AppleTalk networking protocol suite. ... This article does not cite any references or sources. ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ... This article does not cite any references or sources. ... LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... IBM token ring refers to IBMs implementation of token ring technology for linking personal computers in a local area network (LAN). ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ...

Cross platform solutions

The BSD and Linux operating systems support AppleTalk through an open source project called Netatalk, which implements the complete protocol suite and allows them to both act as native file or print servers for Macintoshes, and print to LocalTalk printers over the network. BSD redirects here; for other uses see BSD (disambiguation). ... This article is about operating systems that use the Linux kernel. ... Netatalk is an open-source implementation of the AppleTalk suite of protocols. ...

In addition, Columbia University released the Columbia AppleTalk Package (CAP) which implemented the protocol suite for various Unix flavors including Ultrix, SunOS, *BSD and IRIX. This package is no longer actively maintained. Ultrix (officially all-caps ULTRIX) was the brand name of Digital Equipment Corporations (DEC) native Unix systems. ... SunOS was the version of the UNIX operating system developed by Sun Microsystems for their workstations and server systems until the early 1990s. ... BSD redirects here; for other uses see BSD (disambiguation). ... IRIX is a computer operating system developed by Silicon Graphics, Inc. ...

References

• Inside AppleTalk - original specification for the AppleTalk suite of protocols

See also

• Network File System
• Remote File System
• Samba
• Server Message Block

Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network as easily as if the network devices were attached to its local disks. ... The Remote File System (RFS) was a file access protocol developed by AT&T in the 1980s. ... Samba logo. ... Server Message Block (SMB) is an application-level network protocol mainly applied to shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. ...

External links

• AppleTalk - Directory & Informational Resource