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Do thiếu của bất kỳ nỗ lực đặc biệt để cung cấp các gói tin một cách kịp thời, nó extermely vấn đề thách thức để phát triển thành công các ứng dụng mạng đa phương tiện cho mạng Internet. Cho đến nay, đa phương tiện trên Internet đã đạt được những thành công đáng kể nhưng bị hạn chế. | Differentiated Services manually i.e. the network administrator could load a table of source addresses that are to be marked in a given way into the edge routers or could be done under the control of some yet-to-be-specified signalling protocol. In Figure 6.9-3 all packets meeting a given header condition receive the same marking regardless of the packet arrival rate. In some scenarios it might also be desirable to limit the rate at which packets bearing a given marking are injected into the network. For example an end-user might negotiate a contract with its ISP to receive high priority service but at the same time agree to limit the maximum rate at which it would send packets into the network. That is the end user agrees that its packet sending rate would be within some declared traffic profile. The traffic profile might contain a limit on the peak rate as well as the burstiness of the packet flow as we saw in Section 6.6 with the leaky bucket mechanism. As long as the user sends packets into the network in a way that conforms to the negotiated traffic profile the packets receive their priority marking. On the other hand if the traffic profile is violated the out-of-profile packets might be marked differently might be shaped e.g. delayed so that a maximum rate constraint would be observed or might be dropped at the network edge. The role of the metering function shown in Figure 6.9-4 is to compare the incoming packet flow with the negotiated traffic profile and to determine whether a packet is within the negotiated traffic profile. The actual decision about whether to immediately re-mark forward delay or drop a packet is not specified in the diffserv architecture. The diffserv architecture only provides the framework for performing packet marking and shaping dropping it does not mandate any specific policy for what marking and conditioning shaping or dropping is actually to be done. The hope of course is that the diffserv architectural components are together .
