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Type: TESE
Title: Implementação do protocolo X-25 num concentrador de comunicações baseado no 8088
Author: Madeira, Edmundo Roberto Mauro, 1958-
Advisor: Guimarães, Célio Cardoso, 1942-
Abstract: Resumo: Não informado.

Abstract: This work presents an implementation of the X-25 communication protocol, which is defined for the: CCITT Recommendation (Committee Consultative International Telegraph and Telephone),on an Intel 8088 microprocessador [201, [231 and [36]. The proposed system is based on message exchange. The microprocessor has the function of a concentrator linked to a packet switching network. It will communicate on one side with a network node and on other side with several terminals. The configuration mode between the concentrator and the network node is balanced asynchronous. As an objective, the levels 1 and 2 change through hardware and software a not very reliable point-to-point link into a reliable link. As an second objective, participants in the network exchange traffic information to avoid congestion. The level 3 executes multiplexing to change a single level 2 logical circuit into several independent logical channels. At the level 4 (transport level) some end-to-end control functions are implemented. The levels 2, 3 and 4, in addition to a Manager (Supervisor) and the X-25 line reception and transmission interrupt routines are all treated as concurrent processes. In this work, we also use a formal technique analyse to protocols in such a way as to prevent them against deadlock, unspecified receptions, nonexecutable interactions and state ambiguities as proposed by P. Zafiropulo [19]. We made an analysis of the several levels specifications. An HDLC 8273 interface is used to implement physical the link between the microprocessor and the network. The prototype developed for this thesis possesses two HDLC 8273 interfaces and 32K RAM memory. The programs executed on the 8088 are remotely loaded from the DEC-10 system of the Computing Center. In Chapter I, we describe the ISO architecture and the X-25 protocol. We specify the level 4 used for the purpose of this the sis. State diagram were produced for level 2, from the X-25 protocol specification text for level 3, extracted from the X-25 specification, and for level 4, from the specification of this thesis. In Chapter 11, we formally analyse the X-25 protocol guarantee that it is an error-free protocol. The analysis considers the state diagrams defined in Chapter 1. In Chapter III, we present a brief discussion about concurrent processing languages. where appropriate, comments on Módula 2, the chosen language for the implementation, were included. Communication and synchronization between concurrent processes using monitors and message exchange are presented. Examples. of the X-25 protocol implementation using this two models are shown [3], [81] and [16]. In Chapter IV, which is the thesis body, we treat the implementation on the 8088 microprocessor. The system is .described as a whole and analysed with respect to the following important details: data structures, process communication, non-interrupt modules, dynamic memory allocation, timers, HDLC 8273 interface, etc. In Chapter V, we describe the debugging tests made on the system in a stepwise manner and the conclusion of thesis along with several suggestions were presented in Chapter VI. The main contributions of this thesis were: - Use of formal protocol analysis in a practical implementation of the X-25 protocol. An implementation methodology using message exchange between processes representing the protocol levels and explicit process control transference using the tools implemented in Modula 2.
Subject: Serviços de comunicações
Sistemas telefônicos
Language: Português
Editor: [s.n.]
Date Issue: 1985
Appears in Collections:IC - Tese e Dissertação

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