42 service characteristics cont figure 123 example

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42Service Characteristics (Cont…)FIGURE 1.23 Example Demarcations Points to Describe End-to-End within a NetworkFor services to be useful and effective, they must be described and provisionedend-to-end at all network components between well-defined demarcation points.“End-to-end” does not necessarily mean only from one user’s device to anotheruser’s device. It may be defined between networks, from users to servers, or between specialized devices (Figure 1.23).
43Service Characteristics (Cont…)Services also need to be configurable, measurable, and verifiable within the system.This is necessary to ensure that end users, applications, and devices are getting the services they have requested (and possibly have been paying for), and this leads to accounting and billing for system (including network) resources. Service metrics can be used to measure and verify services and their characteristics.Services are also likely to be hierarchical within the system, with different service types and mechanisms applied at each layer in the hierarchy.
44Service Characteristics (Cont…)FIGURE 1.24 An Example of Service Hierarchy within a Network
45Service LevelsService characteristics can be grouped together to form one or more service levels for the network.There are many ways to describe service levels, includingframe relay committed information rates (CIRs), which are levels of capacity; classes of service (CoSs), which combine delay and capacity characteristics; and IP types of service (ToSs) and qualities of service (QoSs), which prioritize traffic for traffic conditioning functions.Service Characteristics (Cont…)
46Service Characteristics (Cont…)In this example a demarcation of services is shown between the device and network components. Depending on the service requirement or characteristic, however, demarcation may also be between the device and application components.FIGURE 1.25 Service Requests, Offerings, and Metrics
47Service Characteristics (Cont…)System Components and Network ServicesNetwork services are derived from requirements at each of the components in the system. They are end-to-end (between end points that you define) within the system, describing what is expected at each component. Service requirements for the network we are building are derived from each component. There can be user requirements, application requirements, device requirements, and (existing) network requirements. Because we are building the network
48Service Characteristics (Cont…)FIGURE 1.26 Requirements Flow Down Components, from User to Networkservice characteristics are configured and managed within each element and at interfaces between elements. These services are the most specific of all and have the smallest scope (typically a single network device).
49Service Requests and RequirementsService requests and requirements are, in part, distinguished by the degree of predictability needed from the service by the user, application, or device making the request.

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