CATAO, V. S.; http://lattes.cnpq.br/9004848457100237; CATÃO, Vladimir Soares.
Resumo:
Replicated processing on independent processors is a common way to achieve faulttolerant
processing. It is the basis for the reliable processing service offered by the
Seljuk-Amoeba operating environment. In order to assure that the replicated
processes will achieve order and agreement on the input messages received by the
replicas, replicated processing normally uses atomic broadcast protocols. These
protocols assume that communication between any two operational processes is
synchronous, i.e. there is a known finite time bound for message transmission
between any two processes that are executing in accordance with their specification.
In this work, we study the dificulties involved in the development of a synchronous
communication service implemented in software, built on top of conventional
asynchronous networks. In order to overcome these dificulties, we propose a
simulation of a TDMA (Time Division Multiple Access) access method to the
communication media, by which a process can reserve a portion of a TDMA slot
exclusively for its use. The proposal also details the scheduling of the tasks in the
operating system, necessary to assure a time limit not only for the transmission delay
itself, but also to the end-to-end transmission delay for the message ordering
protocols under Seljuk-Amoeba, accounting for the transmission request at the
sending side until the proper delivery of the message at the destination. Besides, we
also suggest a flow control mechanism, in order to guarantee that the process'
transmission requests are compatible with the reservation made on the TDMA slot.