Chapter 3

Transport Protocols

3.1. Introduction

Transport protocols are end-to-end protocols. They are usually included and interpreted by the terminal stations in the network (workstations, servers, telephone sets). Network nodes are usually transparent to such protocols, apart from specific cases where some functions require certain fields to be analyzed (flow classification, Internet Protocol (IP) address and port number translation). Transport protocols can enhance end-to-end performance.

Several transport protocols have been specified (Figure 3.1):

– TCP (Transmission Control Protocol) is a protocol that ensures the delivery to the application layer of error-free data. It provides flow control mechanisms in order to avoid network congestion;

– UDP (User Datagram Protocol) does not respond to variations in the rates provided by the network. It allows error detection only on received data;

– RTP (Real-time Transport Protocol) is used as a complement to the UDP for real-time streams (e.g. voice or video). It carries timing information that allows for the network jitter to be corrected. It enables the detection of segment losses. Like the TCP, it delivers segments to the application sequentially;

– DCCP (Datagram Congestion Control Protocol) is similar to the UDP, upon which it improves, for example with network congestion monitoring;

– SCTP (Stream Control Transmission Protocol) is similar to the TCP. It is mainly employed for server-to-server communications. It supports the ...

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