Xunet 2 Queue Module

The Xunet 1 queue module is designed to allow for experimentation in an operational wide-area network with buffer management strategies and cell service disciplines. The module contains memory to store 512 K cells and implements per-channel queues for up to 32 K virtual circuits. The queue control logic is implemented by table-driven hardware. Queueing policy is administered by an on-board processor called the queue manager. Operation of the module is programmed by downloading code into the queue manager and by downloading tables that are stored in static RAM. The format for an ATM cell used in Xunet reserves bits in the header for congestion signaling: each queue module along a path can read and modify the congestion bits associated with each virtual circuit. This paper summarizes the operation of the queue module and is intended to serve as a guide in programming the module.