Variable-length Exchange Of The Key Technical Analysis And Design

Internet has two challenges, one is the more high speed, another is provide deterministic QoS. There are much technologies would be involved to meet the design, but the most important thing is the switching capability of switch/router.Many high-speed switch/routers we used today are based on the structure of link card and switch backplane, which have the characteristics of high throughput and flexible port configurations. In such a system, every input variable length packet are segmented into fixed length cells. Then the backplane switches the cells to their corresponding output ports based on the information carried by the cell headers. On the output ports, the cells are reassembled to the original packet, and sent out. The switch backplane can be constructed by bus, shared memory and crossbar. And the crossbars are used more commonly in large switching systems. But as explode increase of Internet, the segment and reassemble of packets in traditional switch and the scheduling based on cell limit the improvement of switch capability, and its scalability is rather worse. So we studied a special structure of crossbar in this thesis, which was called as the buffered-crossbar that can support the switching of variable length packets directly. In this structure, every node of crossbar had a small buffer in it, and the scheduler was running based on packet but not cell. With help of modern VLSI technology, this kind of crossbar can be realized economically, also simplified the design of switch/router.It is hard to implement large buffer at each crosspoint with the current technology of VLSI. In order to reflect the performance of CICQ in current situation, we set a small buffer in each crosspoint. But there is a problem: crosspoint can not storage a large packet. In this situation, we use VIQ technology to design a CICQ fabric with output queue which can solve the crosspoint block problem effectively.We research the CICQ switch which can deal with variable length packet directly. Then we built a 16*16 CICQ module in OPNET Moduler. The CICQ module can transfer variable length packet. We study the relationship of buffer size on crosspoints and system performance. At the last, we find the reasonable buffer size which can be used to implement the hardware design.