Padded-frame Based in-sequence Dispatching Scheme for Memory-Memory-Memory (MMM) Clos-network
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摘要: 与其它类型的Clos网络相比，各级带缓存的MMM(Memory-Memory-Memory)Clos网络使得交换网络的配置时间最小化，但是MMM交换中间级缓存的存在会引起输出端口的信元乱序。该文提出了一种满帧填补扩展算法(EPF)，采用逐帧转发的方式来避免MMM Clos网络中的乱序问题。新算法在输入级和输出级采用固定周期轮转方式，中间级采用最早信元优先输出调度，具有复杂度低，可分布式控制，以及不需要缓存加速的特点。分析和仿真结果表明该算法是稳定的，即输入输出为可允许业务时，算法可达100%吞吐率。Abstract: Compared with other types of Clos-netwok switch, the Memory-Memory-Memory (MMM) switch minimizes the time required to configure a Clos-network switch. However the use of buffers in the middle stage of an MMM switch can potentially cause the forwarding of cells to the outputs in out-of-sequence order. A novel scheduling algorithm, called Extended Padded Frame (EPF) scheme, is proposed, which provides in-sequence service for MMM Clos-network by adopting a frame-based approach. The new solution adopts a predetermined cyclic shift configuration at the first and third stages and the oldest-cell-first selection for arbitrations at the second stage. The algorithm is decentralized and requires no speedup. Analysis and simulation results show that the new algorithm is stable, that is to say, EPF can achieve 100% throughput under any admissible traffic patterns.
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Key words:
- Three-stage Clos networks /
- Packet switching /
- Load balancing /
- Maintaining packets order
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