Chapter 15 – Part 2 Networks The Internal Operating System The Architecture of Computer Hardware...

Chapter 15 – Part 2 Networks The Internal Operating System

The Architecture of Computer Hardware and Systems Software:

An Information Technology Approach

3rd Edition, Irv Englander

John Wiley and Sons 2003

Wilson Wong, Bentley College

Linda Senne, Bentley College

Chapter 15The Internal Operating System – Part 2 – Networking

15.2-2

Network Basics Communication paths Protocol standards Data transmission

By character or byte at a time By sending the entire message at a time By subdividing the messages into packets and

sending each packet at a time Frames are packets that have been further

subdivided to meet requirements of the media access control hardware protocol


15.2-3

Packet Header

Also known as the preamble Contains

Description of the packet Destination address of receiver Source address of sender Information about the data being sent


15.2-4

Advantages of Packets Reduces communication overhead Reasonable unit for routing of data Alternative to dedicating a channel for the entire length

of the message Packets from several sources can share a single

channel Each sender/receiver pair appears to have a channel to

itself Receiving computer can process an entire block of data

instead of a character or byte at a time Simplifies synchronization of the sending and receiving

systems by providing clear start and stop points


15.2-5

OSI Reference Model

Open Systems InterconnectionModel

Developed by International Standards Organization (ISO)

Contains seven layers

All People Seem To Need Data Processing

People Do Not Through Sausage Pizza Away

Application Presentation Session Transport Network Data Link Physical


15.2-6

Layers of the OSI Model


15.2-7

OSI Physical Layer

Responsible for transmission of bits Implemented primarily through

hardware Encompasses signaling method,

electrical and mechanical interfaces Example: RS-232, 10Base5


15.2-8

OSI Data Link Layer

Responsible for error-free, reliable transmission of data

Frames sized for compatibility with the MAC protocol

Flow control, error detection and correction, retransmission

Uses MAC addresses


15.2-9

OSI Network Layer Responsible for addressing and routing of

messages to final destination Breaks up messages into frames that meet

the requirements of intervening networks Local network – no routing

Physical address is appended to each packet Symbolic addresses are converted to physical

address through a lookup table External network – routing required

External tables are used to assist in routing message


15.2-10

OSI Transport Layer Ultimate final address of destination is determined All end-to-end communication including intermediate

nodes


15.2-11

OSI Session Layer

Establishes a dialogue between two applications or processes between systems

Terminates connection at end of session

Manages logins, password exchange, logoffs


15.2-12

OSI Presentation Layer

Provides format and code conversion services

Examples File conversion from ASCII to Unicode Encryption, decryption Data reformatting Conversion between data formats used by

different email systems


15.2-13

OSI Application Layer

• Provides utilities and tools for application programs and users


15.2-14

TCP/IP Transmission Control Protocol/Internet Protocol Physical and Data Link layers are not specified by

the TCP/IP protocol Internet Protocol

Implemented in workstations and routers Messages are segmented into packets and are re-

assembled at the other end Uses IP for addressing and routing between networks

Transport Reliable end-to-end connectivity Final delivery of packets

Application


15.2-15

TCP & UDP

Most TCP/IP applications use TCP for transport layer

TCP provides a connection (logical association) between two entities to regulate flow check errors

UDP (User Datagram Protocol) does not maintain a connection, and therefore does not guarantee delivery, preserve sequences, or protect against duplication


15.2-16

Comparison of OSI and TCP/IP


15.2-17

Network Services Protocol Stacks Sockets Network file transfers Print services Web services Messaging services Application program access to network services

RPC – remote procedure calls

Security and network management services Remote processing and login services


15.2-18

Network File Transfers

FTP Internet file transfer protocol

Logical names for machine or drive Windows

Network files can be accessed transparently by being mounted directly into the current file system Unix / Linux


15.2-19

Access for a Networked Operating System


15.2-20

Network Systems

Distributed system Collection of independent computers that appear

to the users of the systems as a single computer

Client-Server system Control is centralized in the server computer Client computers have network access limited to

services provided by the servers

Peer-to-Peer system Any two computers can communicate with one

another within security constraints


15.2-21

Copyright 2003 John Wiley & Sons

All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the permissions Department, John Wiley & Songs, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein.”

Chapter 15 – Part 2 Networks The Internal Operating System The Architecture of Computer Hardware...

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