in the new infrastructure, ircs were connected to the udc in a star network configuration, originally via leased line permanent (not packet switched) connections, based on the x25 protocol, operating at 2.4 kilobits per second (kbit/s). by mid 1981, these private circuit links had been replaced with dedicated 4-wire x25 circuits over the new public packet switch stream (pss) network operating at 4.8 kbit/s.