1. 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

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

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
Chapter 15
The Internal Operating System – Part 2 – Networking

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
Chapter 15
The Internal Operating System – Part 2 – Networking

5. OSI Reference Model Application Presentation Session Transport Network
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

6. Layers of the OSI Model Chapter 15
The Internal Operating System – Part 2 – Networking

7. OSI Physical Layer Responsible for transmission of bits
Implemented primarily through hardware
Encompasses signaling method, electrical and mechanical interfaces
Example: RS-232, 10Base5
Chapter 15
The Internal Operating System – Part 2 – Networking

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
Chapter 15
The Internal Operating System – Part 2 – Networking

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
Chapter 15
The Internal Operating System – Part 2 – Networking

10. 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

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
Chapter 15
The Internal Operating System – Part 2 – Networking

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 systems
Chapter 15
The Internal Operating System – Part 2 – Networking

13. OSI Application Layer
Provides utilities and tools for application programs and users
Chapter 15
The Internal Operating System – Part 2 – Networking

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
Chapter 15
The Internal Operating System – Part 2 – Networking

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
Chapter 15
The Internal Operating System – Part 2 – Networking

16. Comparison of OSI and TCP/IP
Chapter 15
The Internal Operating System – Part 2 – Networking

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
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The Internal Operating System – Part 2 – Networking

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
Chapter 15
The Internal Operating System – Part 2 – Networking

19. Access for a Networked Operating System
Chapter 15
The Internal Operating System – Part 2 – Networking

20. Network Systems Distributed system Client-Server 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

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
The Internal Operating System – Part 2 – Networking