Research Of Large Capacity Switching Network Based On Variable Length Packet

With the continuous expansion of users to internet and the diversification of business types,switching nodes in the core backbone network require more and more switching capacity.The routing switch equipment adopting the time division switch structure and the single stage space division switch structure can not meet the requirements of the switch node for the exchange capacity.Large-capacity routing and switching equipment usually uses multi-level switching fabric.The Clos switch fabric in multi-level switch fabric has good scalability and can be non-blocking.Therefore,in the construction of large-capacity switching network,Clos exchange structure is much favored by the industry.Because IP packet length is not fixed,the traditional large-capacity routing switch equipment usually cut a variable length packet into cells,variable length packets in the form of cells through the exchange of the structure.Although the cell-based switching technology has been very mature,but the cell-based switching system needs to cut the variable length packet and the cell reorganization,so the input port and output port to the switch fabric need to set the packet cutting module and cell reorganization module,increasing the complexity of system design.At the same time cutting the packet and reassembling cell will increase the system delay.Another is to encapsulate the cell,will increase the communication overhead.However,there are few researches on the variable length packet as the transmission unit directly in the large-capacity switching network using Clos structure in China.Therefore,this paper chooses to use variable-length switching as a breakthrough to enhance the switching performance of routing switching equipment.Based on the variable length packet directly as a transmission unit to achieve high-capacity switching network.The main work of this paper can be divided into four parts: basic research,design of exchange architecture,design of function of exchange architecture and simulation modeling.In this paper,the switching fabric and the scheduling algorithm for variable-length switching are studied firstly.Based on the MMM-type Clos structure(Memory-Memory-Memory),a design scheme of large capacity switching network based on variable length packet is proposed.In order to solve the problem of unfairness in the use of variable-length switching lines,this paper introduces a flow scheduling mechanism at the input stage of the MMM-type Clos architecture and a SOL schedulingalgorithm at the middle switching unit of the Clos architecture to schedule the variable-length packets.At the same time,in order to ensure that the switching network can be sustained and stable work,this paper also designed for the switching network token scheduling,traffic control and link failure load balancing and other functions.In the end,this paper simulates the design of large capacity switched network based on variable length packet,and tests the performance of switched network in different scenarios.