All metrics in ALS must be measurable. These measures should be taken and recorded on a regular basis. In general, these measures cover hours of service and availability of services. SLAs are available for almost all types of service, from traditional T-carrier services to frame relays. Internet service providers (ISPs) also offer SLAs for ip-based virtual private networks (VPNs), intranets and ex-trannets. Some ISPs even guarantee a degree of accessibility to their DF Remote Access customers. IBM, for example, offers alS for its remote customers, which guarantees a 95% success rate for DF connections to IBM Global Network. At the same time, ALS is increasingly important to ensure the excellence of business networks. The objective of intracom-pany ALS is to specify, in mutually acceptable measures, what different end-user groups can expect from IT in terms of resource availability and systemic response. SLAs also define what end-users can expect from end-users in terms of using the system and collaborating to maintain and refine service levels over time. SLAs also provide a useful metric for measuring the performance of the IT department. How IT has fulfilled its obligations, as stated in ALS, can determine future human resources, budgets, increases and bonuses. Blake, S., Black, D., et al.
(1998): An architecture for differentiated services. IETF RFC 2475. COMPENSATION Ideally, a back-booking system should be put in place that charges end-users for the resources they consume to provide the service they expect. This encourages business entities to use management methods that optimize costs and performance. If this is not feasible, costs should nevertheless be determined and reported to business units to account for IT resources. The frequency and format of this information should also be described. Another important issue related to the selection of parameters to monitor is the granularity of surveillance. There are three main options: customer-oriented surveillance, virtual system monitoring and physical system monitoring.