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42
Chapter 2
Protocol Attributes
F I G U R E 2 . 7
Connectionless data transfer
Connectionless protocols do not send data relative to any other data
units. The data included in the PDU must contain enough information for
the PDU to get to its destination and for the receiving system to properly pro-
cess it. Because there is no established connection, flow and error control
cannot be implemented. Without flow and error control, the originating sys-
tem has no way of knowing whether all of the transmitted data was received
by the destination system without errors. Table 2.2 shows examples of con-
nectionless protocols.
In this section, you learned the difference between connection-oriented
and connectionless protocols. These protocol characteristics may be found
at any level of the OSI model. The Transport layer, or Layer 4, of the OSI
T A B L E 2 . 2
Connectionless Protocols
Protocol Name
Protocol Description
UDP
UDP (User Datagram Protocol) is a connectionless pro-
tocol used by IP.
AppleTalk DDP
DDP (Datagram Delivery Protocol) is a connectionless
network protocol used for service between two net-
work sockets.
Novell IPX
Novell IPX (Internetwork Packet Exchange) is Novell's
Layer 3 protocol.
Computer A
Computer B
Simple data exchange
No flow or error control is used.
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