Serv per-hop behaviors: Default-The Default behavior provides for best-effort service. Expedited Forwarding-Expedited Forwarding, specified under RFC 2598, defines low latency, or delay, and controlled jitter service. It is tar- geted at VoIP and virtual leased lines. Expedited Forwarding is roughly equivalent to priority queuing, with a safety measure to prevent starvation, and no more than 50% of the link can use Expedited Forwarding. Ingress Interior Egress TCC = traffic classification and conditioning (classification, marking, and policing) PHB = per-hop behavior (queuing and dropping) Figure 8.28 The DiffServ architecture IP QoS Assured Forwarding-Assured Forwarding is specified under RFC 2597. It supports four relative classes of service, and within each class are three lev- els of drop precedents. A congested Assured Forwarding node discards packets with a higher drop preference first. Packets with the lowest drop preference must be within the subscribed profile. Class Selectors-Class Selectors is backward capable with IP precedence. IntServ IntServ, which is specified in RFC 1633, extends the Internet model to support real- time and best-effort services. It provides extensions to the best-effort service model to allow control over end-to-end packet delays, and its key building blocks are resource reservation and admission control. IntServ, a per-flow, resource reservation model, requires Resource Reservation Protocol (RSVP). RSVP allows applications to reserve router bandwidth. Its service provides a bandwidth guarantee and a reliable upper bound to packet delay. RSVP is therefore a resource reservation setup proto- col for the Internet. Its major features include the use of soft state in the routers, receiver-controlled reservation requests, flexible control over sharing of reservations and forwarding of subflows, and the use of IP Multicast for data distribution. Unfortunately, using RSVP on the public Internet is impractical. The resource requirements for running RSVP on a router increase proportionall