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AppleTalk Address Resolution Protocol (AARP) maps the AppleTalk node address used by the datagram delivery protocol to the underlying data link layer addresses. AppleTalk is a protocol suite with an open peer-to-peer architecture running on a variety of transmission media. The AARP resolves AppleTalk addresses to the physical layer, such as the mandatory address control (MAC).
The AARP maps computers' physical hardware addresses to their temporarily assigned AppleTalk network addresses. AARP is functionally equivalent to Address Resolution Protocol (ARP). The AARP table permits management of the address mapping table on the managed device. This protocol allows Apple computers' AppleTalk hosts to generate their own network addresses. It was included in the initial Macintosh version released in 1984.
an AppleTalk machine broadcasts AARP probe packets. It asks for a network address and waits to hear from controllers, such as routers. If addresses are not provided, a single one is picked at random from base subnet 0. To enhance performance, successful addresses are written in non-volitile RAM and used as default addresses in the future.
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 the corresponding AARP. The AARP then supplies the hardware address associated with the network address and checks the active management technology (AMT) to see whether the network address is mapped to any other hardware address. If it is already mapped, the address is passed to the inquiring AppleTalk protocol, which uses it to communicate with the destination. If the address is not mapped, AARP transmits a broadcast, requesting the node using the network address to supply its respective hardware address. When the request reaches the node, it responds with the hardware address. At the same time, if no node exists with the specified network address, no response is transmitted. After trying several times, AARP assumes that the protocol address is not in use and returns an error to the inquiring AppleTalk protocol. If responses are received, the hardware address is associated with the network address in the AMT and is passed to the AppleTalk Protocol, which then uses it to communicate with the destination node.
AARP has well-defined ways to allow the controller devices to override default mechanisms. The concept allows routers to provide information to known addresses and names. On large networks, where AARP causes problems with the introduction of new nodes searching addresses, a router inclusion reduces chattiness. The implementation of AARP into AppleTalk makes it easy to use the networking system.