3G Handset and Network Design

CHAPTER 18

Service Level Agreements

Service Level Agreements (SLAs) are used in private and public networks to define an agreed set of performance metrics being delivered from one party to another or between multiple parties. This chapter addresses all the variables, the specialized needs, quality billing models, and consequent challenges implicit in current and future SLA implementations.

Managing the Variables

If we are to implement a quality-based billing model, an escalating complex of variables must be managed, within prescribed limits, so we can prove we have delivered the quality of service requested and required.

Wireline circuit-switched networks. These SLAs are really simple, specifying how much bandwidth is available, the bit error rate of the bandwidth (typically 1 in 10¹⁰), and network availability (typically 99.999 percent).

Wireless circuit-switched networks. These SLAs are reasonably simple but need to comprehend physical/geographic coverage and dropped call rates. Note that physical/geographic coverage can vary on a day-to-day basis either because of changing propagation conditions or changes in offered traffic loading (creating noise rise at the base station receiver). Wireless circuit-switched performance is therefore less predictable than wireline circuit-switched performance because of the unpredictability introduced by the radio physical layer.

Wireline packet-routed networks. These SLAs need to comprehend a number of additional—and largely unpredictable—variables, ...