scales better than RSVP, and it keeps QoS control local. It pushes the work to the edges of the boundaries and can provide QoS by either customer or network. However, it has no admission control, so too much high-precedence traffic can still swamp the network. DiffServ-DiffServ employs a small, well-defined set of building blocks from which a variety of services can be built. Although DiffServ evolved from the IntServ architecture, DiffServ is a prioritization model with prefer- ential allocation of resources based on traffic classification. DiffServ uses the DSCP to carry information about IP packet service requirements. It classifies traffic by marking IP headers at ingress to the network with flags corresponding to a small number of per-hop behaviors. In other words, queues get different treatments in terms of priority, share of bandwidth, and probability of discard. The DiffServ architecture assumes a relatively small number of feasible queue-scheduling algorithms for high link speeds. It also assumes a large number of individual flows, with many different rules, often being policy driven. The nodes at the edge of the boundaries do the hard work: They group packets explicitly by the per-hop behavior they are to receive (the queue service, the classification, and the conditioning and Chapter 9 IP Services policing of those packets). The nodes in the middle of a cloud only have to deal with traffic aggregates. QoS is managed by local rules within the cloud, and QoS information exchange is limited to boundaries. It is bilateral, not multilateral, and it is not necessarily symmetric. Inter-service provider DiffServ and end-to-end Internet QoS need further standardization and commercial arrangements. Compressed Real-Time Transport Protocol (CRTP)-CRTP is basically RTP compression. Normally, the IP header is 20 bytes, the UDP header is another 8 bytes, and the RTP header is 12 bytes, resulting in a 40-byte header. CRTP can reduce the header to 2 to 4 bytes, which is really useful on slow links. Multi-Class Multi-Li