tion. device that is to be used for this specific traffic. This traffic may be designated as that originating from one or more specific physical ports on the device, that origi- Voice packet prioritization nated from a UDP port within a specified range, or as Prioritization of network traffic is simple in concept: that tagged with specific 802.lp/Q and/or DiffServ code Give important network traffic precedence over un- point values. The assigned queue(s) is(are) then given important network traffic. One prioritization scheme priority over other queues that are used to forward la- assigns priority based on the UDP (User Datagram Pro- tency-insensitive traffic. Though all of these mechanisms tocol) port numbers that the voice packets use. This may be utilized under control of the policy-based man- scheme allows you to use network equipment that can agement system, only UDP port ranges and packet tag- mark the packets on these ports with a priority. UDP is ging via 802.1p/Q and DiffServ are flexible enough to be used to transport voice through the LAN because, unlike used entirely under software control interests and are the TCP, it is not connection-based. Because of the human services that provide low latency and constant delay as is ear's sensitivity to delay, it is better to drop packets required for good voice quality. rather than retransmit voice in a real-time environment. Prioritization is also called CoS (class of service) because traffic is classed into categories such as high, medium, Jitter and low (gold, silver, and bronze), and the lower the Perhaps the one aspect of IP networks that makes them priority, the more "drop eligible" is a packet. E-mail and fundamentally different from circuit-switched networks Web traffic is often placed in the lowest categories. When is variance in propagation delay, or jitter. Audio encoding/ the network gets busy, packets from the lowest cate- decoding is basically a synchronous process: The analog gories are dropped first. signal is sampled at prescribed intervals, the