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Introduction:
AppleTalk, a protocol suite developed by Apple Computer in the early 1980â„¢s.
 AppleTalk's purpose was to allow multiple users to share resources, such as files and printers. The devices that
supply these resources are called servers.
 AppleTalk was designed with a transparent network interfaceâ€that is, the interaction between client computers and
network servers requires little interaction from the user.
 Two versions of AppleTalk exist:
AppleTalk Phase 1
AppleTalk Phase 2
link layer.
2.AppleTalk Network Components
Sockets
Networks
Non-extended Networks
Extended Networks
Nodes
Zones
The AppleTalk Internetwork Consists of a Hierarchy of Components
Socket:
An AppleTalk socket is a unique, addressable location in an AppleTalk node.
Sockets can be assigned statically or dynamically.
Socket Clients Use Sockets to Send and Receive Datagrams
Zones: An AppleTalk zone is a logical group of nodes or networks that is defined when the network
administrator configures the network.
Networks
AppleTalk network consists of a single logical cable and multiple attached nodes.
The logical cable is comprised of either a single physical cable or multiple physiÂÂcal cables interconnected by
using bridges or routers.
AppleTalk networks can be classified into two types
Non extended network
Extended network.
AppleTalk Physical and Data link LayersEtherTalk EtherTalk Link Access Protocol LocalTalk
LocalTalk Link Access Protocol TokenTalk TokenTalk Link Access Protocol
Local TalkLocalTalk networks are organized in a bus topology, which means that devices are connected to each other
in series.Local Talk Link Access Protocol: The LocalTalk Link Access Protocol (LLAP) is the media-access
protocol used in LocalTalk networks to provide best-effort, error-free delivery of frames between AppleTalk nodes
Token Talk: supporting the same speeds and the same number of active network nodes. Token Talk Link Access
Protocol: The Token Talk Link Access Protocol (TLAP) handles the interaction between the proprietary
AppleTalk protocols and the standard data link layer.
Network Addresses
Network number†A 16-bit value that identifies a specific AppleTalk network (either non extended or extended)
Node number†An 8-bit value that identifies a particular AppleTalk node attached to the specified network
Socket number†An 8-bit number that identifies a specific socket running on a network node
AppleTalk Address Resolution
Address Mapping Table
Each AppleTalk node contains an Address Mapping Table (AMT), where hardware addresses are associated with
network addresses.
Address Gleaning
This process of obtaining address mappings from incoming packets is known as address gleaning.
AARP Operation
The AppleTalk Address Resolution Protocol (AARP) maps hardware addresses to network addresses. When an
AppleTalk protocol has data to send, it passes the network address of the destination node to AARP.
Figure : The AppleTalk Network Address Consists of Three Distinct Numbers
D D P Overview:
DDP TransmissionProcess
The Datagram Delivery Protocol (DDP) is the primary network layer routing protocol in the AppleTalk protocol suite
that provides a best-effort connectionless datagram service between AppleTalk sockets.
AppleTalk Protocol Suite
DDP Packet Format
The following descriptions summarize the fields associated with the DDP packets. This packet has two forms:
Short DDP packetâ€The short format is used for transmissions between two nodes on the same network segment in a non
extended network only. This format is seldom used in new networks.
Extended DDP packetâ€The extended format is used for transmissions between nodes with different network numbers (in
a no extended network) and for any transmissions in an extended network.
An Extended DDP Packet Consists of 13 Fields: