he IPv6 The Next-Generation Network Infrastructure Real-Time Application RTP and RTCP Real-Time Server Router Router RTP RTP RTCP Control Information Control Info RTP and RSVP Real-Time Recipient Application Figure 10.13 RSVP and related protocols Traffic Class octet, is used to mark a packet to receive a particular forwarding treat- ment or per-hop behavior at each network node. For this reason, DiffServ is really a CoS model: It differentiates traffic by prioritizing the streams, but it does not allow the specification and control of traffic parameters. DiffServ differentiates traffic by user, service requirement, and other criteria. It then marks the packets so that the network nodes can provide different levels of service via priority queuing or band- width allocation, or by choosing dedicated routes for specific traffic flows. DiffServ scheduling and queue management allow routers to act on the IP datagram. Service allocation is controlled by a policy management system. Routers can do four things after receiving an IP datagram: manage a queue, schedule interfaces, select which datagram is the logical choice for discard, and select an outbound interface. Router How much bandwidth? Delay? Drop? CoS maps multiple flows to a few service levels, reducing network burdens while increasing service quality Figure 10.14 DiffServ Chapter 10 Next-Generation Networks DiffServ is a prioritization model with preferential allocation of resources based on traffic classification. As discussed in Chapter 8, DiffServ uses a DiffServ Code Point (DSCP) to select the service-that is, the per-hop behavior-that the packet will receive at each DiffServ-capable node. Queues then get different treat- ment in terms of priority, share of bandwidth, or probability of discard. Class-Based Queuing (CBQ) is a QoS tactic based on traffic management algo- rithms deployed at the WAN edge. CBQ is a fully open, nonproprietary technology that brings bandwidth-controlled CoS to IP network infrastructures. It allows traf- fic to be prioritized accor