Four versions of ISDN BRI network modules are available. Each 4- and 8-port module has the option of an S/T interface or an onboard NT1 for each port. Local static RAM (SRAM) is used for buffer descriptors and input queues. The 4-port module is not field upgradeable to the 8-port module. With all eight BRI ports running continuous data (144 kbps each) and 50-byte packets, the maximum performance possible is 5760 pps and an aggregate full-duplex data rate of 2.3 Mbps.
