Mechanisms for Dynamic Service Quality Control The means of dynamically controlling service quality in IP networks is our next topic. There are two primary uses for such methods: dynamic control of resources within an IP domain, and implementation of dynamic SLAs between domains. The generic element handling both of these tasks is often called the “bandwidth broker” (BB), and this convention is followed also within this book. Admission control or service quality instantiation control is not part of the basic DiffServ framework [RFC2475]. Subsequently, the need for IP service quality support mechanisms for DiffServ networks other than edge provisioning and per-hop. | 8 Mechanisms for Dynamic Service Quality Control The means of dynamically controlling service quality in IP networks is our next topic. There are two primary uses for such methods dynamic control of resources within an IP domain and implementation of dynamic SLAs between domains. The generic element handling both of these tasks is often called the bandwidth broker BB and this convention is followed also within this book. Admission control or service quality instantiation control is not part of the basic DiffServ framework RFC2475 . Subsequently the need for IP service quality support mechanisms for DiffServ networks other than edge provisioning and per-hop prioritization mechanisms in core networks has been widely acknowledged RFC2638 Sch98 THD 99 TAP 01 JC01 SAF 01 TIPHON-3 . The basic reason for the need of dynamic perdomain service quality control mechanism is the following up to a limit service quality for critical service types can be provided by mapping them to a proper service quality support aggregate such as EF. This works because of the prioritization mechanism of DiffServ. Alas when there is too much traffic within the EF PSC the flows sharing the PHB begin to suffer. The effect of EF PHB to other PSCs within the router can be controlled by using rate limiters but basic DiffServ framework does not provide tools for Implementing Service Quality in IP Networks Vilho Raisanen 2003 John Wiley Sons Ltd ISBN 0-470-84793-X 252 MECHANISMS FOR DYNAMIC SERVICE QUALITY CONTROL dynamic control within the aggregate. Similarly the quality in AF PSCs suffers from too many service instances trying to share them. The end-user SLAs at the edge of the network are imposed by policing of traffic at the edge of the DiffServ domain. As we saw in Chapter 3 policing requires that adequate DiffServ classifier be placed at the edge of the network. With statically configured DiffServ classifiers only it is not possible to perform dynamical resource control. Basically two techniques
