tailieunhanh - IP-Based Next-Generation Wireless Networks phần 10

để đạt được mục tiêu này. Sau khi MN là xác thực thành công và ủy quyền, máy chủ Đường kính nhà phân phối các phím phiên. Ba phím được tạo ra: MN-HA phím (K1), chính MN-FA (K2), và chính FA-HA (K3) 0,4 K1 được sử dụng giữa MN và HA. K2 được sử dụng giữa MN và FA. | 372 QUALITY OF SERVICE condition traffic according to the Service Level Specification SLS 30 . The DS field contains a DS Code Point DSCP a tag that specifies the forwarding Per-Hop Behavior PHB for that packet. A PHB might simply specify dropping precedence. It might also include other performance characteristics. When packets enter the DS domain they pass through a Diff-Serv edge router. They are then forwarded by Diff-Serv core routers. If a packet is not already classified the edge router performs classification. The edge router may also reclassify the packet if the classification by access router does not conform to the SLS. The edge router assigns packets to a Behavior Aggregate BA . A behavior aggregate is a collection of packets with the same DSCP and is associated with a specific PHB. Packets then are subject to the parameters described in a Traffic Conditioning Specification TCS between their Diff-Serv domain and the customer s access network. The edge router also performs important conditioning functions to keep PHBs in profile with the TCS. Conditioning functions include metering marking shaping and dropping policing. Ingress edge routers hence can assure traffic is conformed with the TCS. Inside the DS domain packets are forwarded aggregately rather than individually according to the PHB. Traffic may pass through multiple DS domains maintained by different service providers as shown in Figure . The egress edge router of a DS domain may perform traffic conditioning according to a TCS with the next DS domain. Packet Classification and Conditioning Based on the functional model illustrated in Figure and the discussion above traffic classification and conditioning are the foremost processes in Diff-Serv. The details of traffic classification and conditioning are furthered depicted in Figure . Fig. Packet classification and conditioning INTERNET QoS 373 Packet classifier is an entity that selects packets based on the content of .