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Ví dụ như mạng Lật Bat76 topo là giống hệt với mạng Omega đảo ngược và thao túng dữ liệu thay đổi [Wu80a là topo giống hệt với một đảo ngược SW-đa. Kể từ khi mỗi chuyển đổchuyển mạch tối thiểu, tìm hiểu Networks Chặni | 160 The ATM Switch Model are unbuffered IN queueing . In this last case input and output queueing whenever adopted take place at IPC and OPC respectively whereas shared queueing is accomplished by means of additional hardware associated with the IN. Figure 5.2. Model of ATM switch In general two types of conflict characterize the switching operation in the interconnection network in each slot the internal conflicts and the external conflicts. The former occur when two I O paths compete for the same internal resource that is the same interstage link in a multistage arrangement whereas the latter take place when more than K packets are switched in the same slot to the same OPC we are assuming for simplicity K. 1 . An ATM interconnection network N X N with speed-up K K N is said to be non-blocking K-rearrangeable according to the definition given in Section 3.2.3 if it guarantees absence of internal conflicts for any arbitrary switching configuration free from external conflicts for the given network speed-up value K. That is a non-blocking IN is able to transfer to the OPCs up to N packets per slot in which at most K of them address the same switch output. Note that the adoption of output queues either in an SE or in the IN is strictly related to a full exploitation of the speed-up in fact a structure with K 1 does not require output queues since the output interface is able to transmit downstream one packet per slot. Whenever queues are placed in different elements of the ATM switch e.g. SE queueing as well as input or shared queueing coupled with output queueing in IN queueing two different internal transfer modes can be adopted backpressure BP in which by means of a suitable backward signalling the number of packets actually switched to each downstream queue is limited to the current storage capability of the queue in this case all the other head-of-line HOL cells remain stored in their respective upstream queue queue loss QL in which cell loss takes place in the
