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چکیده
Vaidya paper: A mutual exclusion algorithm for ad hoc mobile networks Recall, their network model, changing graph, with links coming and going at any time. Managed mutual exclusion using a token traveling through the changing network. Used Gafni-Bertsekas link reversal ideas to maintain a token-oriented DAG (rather than a destination-oriented DAG as in GB). A node that receives the token may lower its height (differs from GB, where nodes only raise their heights), to ensure that its new height is lower than that of the neighbor who sent the token. Nodes still raise their heights, as in GB, to maintain the token-directed DAG property. Last time I described the algorithm in some detail—how the nodes respond to various input events, including requests to obtain and release the critical section, message arrivals, and LinkUp and LinkDown notifications. I won't repeat this—refer to my notes or the paper. Highlights: Requesting the critical section: Enqueues its own identifier i on its queue. If it has the token, then calls GiveTokenToNext(). If not, calls ForwardRequest(). GiveTokenToNext(): Dequeues first element of queue. If it's i itself, it grants the resource to the local application. If not, it's a neighbor j; then i sends the Token to j, and resets next := j. To accommodate the movement of the token to j:
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