Information Technology Reference
In-Depth Information
As defined by Apple Computer, AURP converts RTMP and ZIP packets into AURP packets
and vice versa. As implemented by Cisco, AURP converts Enhanced IGRP packets as well
as RTMP and ZIP packets.
Note
AEP
AEP is an extremely simple protocol which generates packets that can be used to test the reachability of
various network nodes.
ATP
ATP is suitable for transaction-based applications such as those found in banks or retail stores. ATP
transactions consist of requests (from clients) and replies (from servers). Each request/reply pair has a
particular transaction ID. Transactions occur between two socket clients. ATP uses exactly once (XO)
and at-least-once (ALO) transactions. XO transactions are used in situations where performing the
transaction more than once would be unacceptable. Banking transactions are examples of transactions
that, if performed more than once, result in invalid data.
ATP is capable of most important transport-layer functions, including data acknowledgment and
retransmission, packet sequencing, and fragmentation and reassembly. ATP limits message
segmentation to eight packets, and ATP packets cannot contain more than 578 data bytes.
Upper-Layer Protocols
AppleTalk supports several upper-layer protocols:
AppleTalk Data Stream Protocol (ADSP) establishes and maintains full-duplex data streams
between two sockets in an AppleTalk internetwork. ADSP is a reliable protocol in that it guarantees
that data bytes are delivered in the same order as sent and that they are not duplicated. ADSP
numbers each data byte to keep track of the individual elements of the data stream. ADSP also
specifies a flow-control mechanism. The destination can essentially slow source transmissions by
reducing the size of its advertised receive window. ADSP also provides an out-of-band control
message mechanism. Attention packets are used as the vehicle for moving out-of-band control
messages between two AppleTalk entities. These packets use a separate sequence number stream to
differentiate them from normal ADSP data packets.
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The AppleTalk Session Protocol (ASP) establishes and maintains sessions (logical conversations)
between an AppleTalk client and a server.
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AppleTalk's Printer Access Protocol (PAP) is a connection-oriented protocol that establishes and
maintains connections between clients and servers. (Use of the term
printer
in this protocol's title
is purely historical.)
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The AppleTalk Filing Protocol (AFP) helps clients share server files across a network.
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