DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

the response are very short. There is no need to divide the query or response between multiple packets, so the complexity of TCP is not required. If there is no response to the query after a period of time, the query can simply be resent.

The User Datagram Protocol (UDP) is designed for communications that do not require division among multiple packets and subsequent reassembly. UDP does not keep track of what is sent.

UDP uses port numbers in a way that is directly analogous to TCP. There are well-known UDP port numbers for servers that use UDP.

Figure 5-13. Ethernet Packet Header

The UDP header is shorter than a TCP header. UDP also uses a checksum to verify that data is received uncorrupted.

The Internet Control Message Protocol (ICMP) is also a simplified protocol used for error messages and messages used by TCP/IP. ICMP, like UDP, processes messages that will fit into a single packet. ICMP does not, however use ports because its messages are processed by the network software.

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Switch Management and Operating Concepts

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D-Link DES-3326S manual Ethernet Packet Header, 104