Office of the Manager National Communications System

C u r rently the IP version 4 (IPv4) header includes a field called “Type of Service” (TO S ) intended to indicate the quality of service (QOS) Internet packets should receive. QOS, a m e a s u rement for Internet traffic, quantifies d e l a y, throughput, and reliability that an Internet packet or packet stream is re c e i v i n g . D i ff e rent kinds of Internet traffic re q u i re d i ffering QOS levels. Some types of data (e.g., e l e c t ronic mail) can tolerate a lower QOS because packets can be buff e red and, if lost, resent with little impact on the user. For both voice and video, which are real-time services, even a small delay in communications p roduces a noticeable degradation of service for users.