Distributed mutual exclusion token-permission based by prioritized groups

Sites with the same priority are gathered in the same group. Communication inside a group is organized in a logical rooted tree structure. The tree´s root is the site that last held the token. This organization is similar to that of Raymond´s algorithm (1989). For its external communications, a group resorts to an external supplementary element: a router. This router manages external communications. The communication protocol between routers is similar to that of Ricart-Agrawala (1981). Priority between routers is carried out by a comparison mechanism. When it receives a permission request from a router having priority, a router temporarily suspends the request execution of its global waiting queue