Chapter 7. Establishing VoIP SLAs
Uptime and bandwidth: ISP sells and you buy. Trust, but verify.
This chapter explains the service-level agreements that are needed for a VoIP implementation. SLAs have become a common means of defining how network performance is measured and guaranteed by service providers. The concept of SLA management was introduced in Chapter 6, "Ongoing VoIP Management," as part of network performance management. This chapter goes into more detail and discusses some typical SLAs for VoIP, the metrics these SLAs are based on, and how to implement a VoIP SLAwithin your organization or with a service provider.
An SLA is exactly what the name impliesan agreement between two parties about the delivery of a certain level of service. Why should you consider implementing an SLA? Because you are depending on a service provider, such as an ISP, to deliver a service, such as WAN access, that meets certain quality expectations. And when the delivered service does not meet those expectations, it costs youboth time and money. An SLA can help you recover some of the cost incurred during a period of degraded or unavailable service. Equally, an SLA can represent a promise you make to VoIP phone users for a guaranteed level of quality and availability. But in either case, to create an effective SLA, you need to consider what you want to measure when evaluating the service and what expectations you and your network's users have for the network service provided.