voice call server configures media instance, basic PCM audio encoding is, by definition, processor resources and the terminals involved in the call a synchronous process; IP network transport is, by to use the appropriate values for the (sub)network(s) to design, an asynchronous process. Traditional circuit which they are attached. Typically, these values will be switching provides dedicated, clocked resources for uniform throughout the network, but allowances are lockstep transmission; packet transmission is subject to made for different parts of the network to utilize dif- unpredictable delays and losses. The network admin- ferent Diff-Serv and/or 802. 1p/Q values to designate istrator's job is to use the QoS features to minimize the the same service. effects of IP network "unpredictability." In order for voice traffic to receive excellent quality in In a converged network, the voice call/feature server a converged network, the network infrastructure equip- plays a central role in ensuring that the available QoS ment, i.e., industry standard IP switches and routers, and mechanisms are appropriately utilized SO that voice the voice endpoints, which include the telephones, traffic receives appropriate treatment in the network softphones, and gateways, must be configured in a con- consistent with business policies regarding network uti- sistent manner SO that voice packets are appropriately lization. This section describes the QoS mechanisms tagged and, consequently, properly identified and available in a converged network and how the call server forwarded expeditiously. QoS architecture employs controls their use. IP-based QoS mechanisms can be a policy-based network management system to consis- utilized to provide the best possible end-to-end audio tently configure the network and the voice call/feature experience when all or part of the audio path is carried server with QoS parameter values. The voice call/feature over packet-switched networks. "Best," in this context, is server is, in turn, responsible for con