3G Handset and Network Design

CHAPTER 17

Traffic Shaping Protocols

In the previous chapter, we discussed the fact that circuit switching was designed to move essentially constant rate traffic from users at one side of the network to users at the other side of the network (or networks). In this chapter we look at how session value is developed on the basis of session persistency and how this, in turn, has an impact on traffic shaping protocols. We examine the hardware and software performance constraints in a typical router—how router hardware and software introduces delay and delay variability when presented with highly asynchronous traffic. We also identify the important issue of policy complexity. How policy complexity is increasing over time and why this presents a challenge to Internet Protocol performance.

An Overview of Circuit Switching

Circuit switching works on a number of well-defined and relatively constant rule sets. A call request comes in with a destination (a telephone number), and a path is established between sender and receiver (actually two paths: an uplink and downlink); the path is then maintained for the duration of the call and then cleared down and billed. There is no buffering involved, so the end-to-end performance is deterministic and consistent over time. The queuing behavior of voice traffic is well understood, so circuit-switched capacity can be provisioned to reduce blocking to an effectively unnoticeable level—that is, five niness availability, meaning it is available 99.999 ...