Router Switch GigE UNI FR UNI Figure 10.11 Migrating to a multiservice network The Next-Generation Network Infrastructure and pseudo-wire emulation edge to edge, along with interworking standards for Frame Relay and ATM. Support for a wide variety of interfaces-The multiservice edge must sup- port various protocols, such as Frame Relay, ATM, GigE, and PoS. Support for both network and service interworking-The multiservice edge must support both network and service interworking. Multiservice switches support interworking of Frame Relay and ATM services today. Multiservice edge devices must also support network interworking, such as the ATM-MPLS network interworking specification, allowing them to act as gateways between Layer 2 and Layer 3 networks. (For detailed informa- tion and updates on the various service and network interworking specifi- cations available for Frame Relay, ATM, and MPLS, consult the MFA Forum site, at www.mfaforum.org.) Quality of Service As mentioned throughout this chapter and others, QoS issues play a very impor- tant role in next-generation networks. It is becoming increasingly important to provide for very granulated levels of service, thereby allowing very high perfor- mance and at the same time creating platforms for multitudes of new revenue- generating services. QoS is the ability to provide different levels of service to differently character- ize traffic or traffic flows. It constitutes the basis for offering various classes of ser- vice to different applications or segments of end users. This then allows the creation of different pricing tiers that correspond to the different CoS and QoS lev- els. QoS is essential to the deployment of real-time traffic, such as voice or video services, as well as to the deployment of tiered data services. QoS includes definitions of the network bandwidth requirements, the user pri- ority control, control of packet or cell loss, and control of delay-both transit delay (which is end to end) and traffic delay variations (i.e., jitter). Traffic chara