Traffic Types

Different types of traffic have different sensitivities to delay, jitter, and packet loss: there is no “one size fits all” recipe. Thus, the focus of this chapter is not to describe every single possible type of traffic but rather focus on three specific subjects: the Transport Control Protocol (TCP) protocol, real-time traffic, and the evolution of user session durations.

TCP is a widely deployed transport protocol used at Layer 4 in the OSI model. It is a popular transport protocol because it provides flow control and traffic retransmission in the case of packet loss. This chapter discusses how the features of TCP fit into the QOS realm. Real-time traffic encompasses a huge range of different applications and services and in this chapter, we will focus on the common dynamics and requirements shared by all of them in regards to QOS. Finally, this chapter examines the duration of the session, and here we examine what changes if the traffic flow lasts a few seconds, or a few hours, and compare the long-lasting session with the short session.

4.1 Anatomy of the TCP Protocol

Transport Control Protocol (TCP) is an extremely popular protocol used for transport at Layer 4 of the OSI model. Numerous papers and books describe the TCP protocol in detail, several of them referenced in the further reading section of this chapter. TCP is defined in RFC 793 [1]. The main goal of this chapter is to arm the reader with the knowledge to understand key terms such as “TCP slow start” ...

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