Telecommunications Signaling
Highlights the conventions of signalling systems and provides a detailed assessment of their architecture.
TABLE OF CONTENTS Telecommunications Signaling
18.6: User Datagram Protocol (UDP)
18.6 User Datagram Protocol (UDP)
Like TCP, the User Datagram Protocol (UDP)5 provides a communications capability between hosts belonging to interconnected networks. However, UDP is designed to minimise signalling overheads by keeping the protocol simple and using connectionless procedures. As a result, the delivery of data using UDP is not guaranteed and duplication can occur.
18.6.1 Architecture
UDP fits within the host-to-host layer of the IP Model, as illustrated in Fig. 18.3. UDP makes use of the Internet Layer to provide network functions (typically the IP). It supplies services to the Application Layer and users.
18.6.2 Format
Data is transferred Between the UDP and the lower layer (IP in this example) in 'UDP Datagrams'. The UDP adds its header to the data transferred from the user, before passing the whole datagram to the lower layer (e.g. IP). Each datagram header contains address, length and checksum fields. The format of the Datagram is illustrated in Fig. 18.10.
| Source Port (16) | Destination Port (16) |
| Length (16) | Checksum (16) |
| Data |
Figure 18.10: User Datagram Format
The Source Port is an optional field and identifies the sending user. In connectionless communications, responses are often not required. If a response is given, the Source Port is the address within the host to which the response is delivered. The Destination Port identifies the destination user address within a host. The host itself is identified by the header of the lower layer, e.g. the Destination Address within the IP packet. The Length Field gives the total length...
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