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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

㈰〳


Wilson Wong, Bentley College

Linda Senne, Bentley College

Chapter 15

The Internal Operating System


Part 2


Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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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


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The Internal Operating System


Part 2


Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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OSI Reference Model


Open Systems
Interconnection

Model


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

Chapter 15

The Internal Operating System


Part 2


Networking

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Layers of the OSI Model

Chapter 15

The Internal Operating System


Part 2


Networking

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OSI Physical Layer


Responsible for transmission of bits


Implemented primarily through
hardware


Encompasses signaling method,
electrical and mechanical interfaces


Example: RS
-
232, 10Base5

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The Internal Operating System


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Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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OSI Transport Layer


Ultimate final address of destination is determined


All end
-
to
-
end communication including intermediate
nodes

Chapter 15

The Internal Operating System


Part 2


Networking

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OSI Session Layer


Establishes a dialogue between two
applications or processes between
systems


Terminates connection at end of
session


Manages logins, password
exchange, logoffs

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The Internal Operating System


Part 2


Networking

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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

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The Internal Operating System


Part 2


Networking

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OSI Application Layer


Provides utilities and tools for
application programs and users

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The Internal Operating System


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Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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Comparison of OSI and TCP/IP

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The Internal Operating System


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Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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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

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The Internal Operating System


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Networking

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Access for a Networked

Operating System

Chapter 15

The Internal Operating System


Part 2


Networking

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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

Chapter 15

The Internal Operating System


Part 2


Networking

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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
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Department, John Wiley & Songs, Inc. The purchaser
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-
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