a Terminal Interface Processor (TIP), which provided terminal server support for up to 63 ASCII serial terminals through a multi-line controller in place of one of the hosts. The 316 featured a greater degree of integration than the 516, which made it less expensive and easier to maintain. The 316 was configured with 40 kB of core memory for a TIP. The size of core memory was later increased, to 32 kB for the IMPs, and 56 kB for TIPs, in 1973. In 1975, BBN introduced IMP software running on the Pluribus multi-processor. These appeared in a few sites. In 1981, BBN introduced IMP software running on its own C/30 processor product. Network performance In 1968, Roberts contracted with Kleinrock to measure the performance of the network and find areas for improvement. Building on his earlier work on queueing theory, Kleinrock specified mathematical models of the performance of packet-switched networks, which underpinned the development of the ARPANET as it expanded rapidly in the early 1970s. Operation ARPA was intended to fund advanced research. The ARPANET was a research project that was communications-oriented, rather than user-oriented in design. Nonetheless, in the summer of 1975, operational control of the ARPANET passed to the Defense Communications Agency. At about this time, the first ARPANET encryption devices were deployed to support classified traffic. The transatlantic connectivity with NORSAR and UCL later evolved into the SATNET. The ARPANET, SATNET and PRNET were interconnected in 1977. The ARPANET Completion Report, published in 1981 jointly by BBN and DARPA, concludes that: CSNET, expansion Access to the ARPANET was expanded in 1981, when the National Science Foundation (NSF) funded the Computer Science Network (CSNET). Adoption of TCP/IP The DoD made TCP/IP the standard communication protocol for all military computer networking in 1980. NORSAR and University College London left the ARPANET and began using TCP/IP over SATNET in early 1982. On January 1, 1983, known as flag day, TCP/IP protocols became the standard for the ARPANET, replacing the earlier Network Control Protocol. MILNET, phasing out In September 1984 work was completed on restructuring the ARPANET giving U.S. military sites their own Military Network (MILNET) for unclassified defense department communications. Both networks carried unclassified information, and were connected at a small number of controlled gateways which would allow total separation in the event of an emergency. MILNET was part of the Defense Data Network (DDN). Separating the civil and military