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Distributed Systems (Communication Protocols (Physical Layer (It is…
Distributed Systems
Communication Protocols
The International Standards Organization created the OSI model for describing the various layers of networking which are described below.
Physical Layer
It is responsible for handling both the mechanical and the electrical details of the physical transmission of a bit stream
Data-Link Layer
The data-link layer is responsible for handling frames, or fixed-length parts of packets
Network Layer
Responsible for breaking messages into packets, providing connections between logical addresses, and routing packets in the communication network
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Session Layer
Responsible for implementing sessions, or process-to-process communication protocols.
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Advantages
Resource Sharing
Provides mechanisms for sharing files at remote sites, processing information in a distributed database, printing files at remote sites, using remote specialized hardware devices, and performing other operations.
Computation Speedup
If a particular computation can be partitioned into subcomputations that can run concurrently, then a distributed system allows us to distribute the subcomputations among the various sites and speeding up the computation time.
Reliability
If one site fails in a distributed system, the remaining sites can continue operating, giving the system better reliability.
Communication
By transferring the files of the project, logging in to each other’s remote systems to run programs, and exchanging mail to coordinate the work, users minimize the limitations inherent in longdistance work.
Communication Structure
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Routing Strategies
What Is?
When a process at site A wants to communicate with a process at site B, how is the message sent?
If there is only one physical path from A to B, the message must be sent through that path.
If there are multiple physical paths then each site has a routing table indicating the alternative paths that can be used to send a message to other sites
Connection Strategies
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Pairs of processes that want to communicate over the network can be connected via circuit switching, message switching, or packet switching.
Packet Strategies
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If a message is too long to fit within one packet, or if the packets need to flow back and forth between the two communicators.
Network-bases OS
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Network Structure
Local Area Network (LAN)
Designed to cover a small geographical area, and they are generally used in an office environment
The communication links tend to have a higher speed and lower error rate than do their counterparts in wide-area networks.
A typical LAN may consist of a number of different computers, various shared peripheral devices, and one or more routers that provide access to other networks
Wide Area Network
Physically distributed over a large geographical area, the communication links are, by default, relatively slow and unreliable.
Communication links are controlled by special communication processors, commonly known as gateway routers or simply routers.
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TEC, Sede Central Cartago, Escuela de Computacion, Sistemas Operativos Reporte #13 - Operating System Concepts - Capitulo 17 - Distributed Systems Guilliano Dambrosio Soza, 2017158561 28/10/2019, II Semestre, Esteban Arias