Networking and Internet
1. Network Fundamentals
- Network Classifications: Scope:
o Personal Area Network (PAN)
o Local Area Network (LAN)
o Metropolitan area (MAN)
o Wide Area Network (WAN)
o Internet
- Network topology: bus and star
- Protocols: A set of rules that defines how data is formatted and processed on a network:
CSMA/CD ( Used in Ethernet); CSMA/CA (Used in Wifi)
- Open system: A system that based on a common model of network architecture and an
accompanying suite of protocols
- Proprietary system: A system that uses technologies kept private by a particular commercial
vendor.
-  Interoperability: The ability of software and hardware on multiple machines and from
multiple commercial vendors to communicate.
Client/Server: One server + many clients, Serve must execute continuously, Client initiates
communication.
Server: be prepared to serve multiple clinets at any time
(P2P): Peers communicate as equals on a one-to-one basis: two processes communicating as
equals. Peer processes can be short-lived.
- Connecting Networks
o Repeater: Extends a network
o Bridge: Connect two compatible networks
o Switch: Connect several compartible networks
o Router: Connect two incompartible networks resulting in a network of networks called
an Internet.
- Wireless and mobile connection:
Bluetooth, Zigbee, RFID, 3G/4G/5G
2. The Internet: An internet that spans the world.
- Original goal: to develop a means of connecting networks that would not be disrupted by
local disaster.
- Today: A commercial undertaking that links a worldwide combination of PANs, LANs, MANs
and WANs involving millions of computers.
- Test with tracert, ping commands
- Internet Architecture:
o Internet Service Provider (ISP): Tier-1, Tier-2
o Acess or Tier-3 ISP: Provides connectivity to the Internet: Hotpot (Wireless), Telephone
lines, Cable/Satellite systems DSL, Fiber optics.
-
Internet Addressing: IP Address: (32bits or 128 bits): represented in dotted decimal
notation.
o Mnemonic address: Domain names + Top-Level Domains
o Domain name system (DNS): Name servers + DNS lookup
- Internet Corporation for Assigned Names & Numbers (ICANN):
o Allocates IP Addresses to ISPs who then assign those addresses within their region.
o Oversees the registration of domains and domain names
- Early Internet Applications
o Network News Transfer Protocol (NNTP)
o File Transfer Protocol (FTP)
o Telnet and SSH
o Hypertext Transfer Protocol (HTTP)
o Electronic Mail (email):
 Domain mail server collects incoming mail and transmits outing mail.
 Mail server delivers collected incoming mail to clients via POP3 or IMAP.
- More Recent Applications
o Voice Over IP (VoIP)
o Internet Multimedia Streaming: Unicast, Multicast, On-demand streaming, Content
delivery networks (CDNs)
3. The World Wide Web
Hypertext: Combines internet technology with concept of linked-documents. (Embeds
Hyperlinks to other documents)
Browsers: present materials to the user
Webservers: provide access to documents ( identified by URLs and transferred using HTTP)
Hypertext Markup Language (HTML)
Encoded as text file
Contains tags to communicate with browser
o Appearance:
 <h1> to start a level one heading
 <p> to start a new paragraph
o Links to other documents and content
 <a href = …>
o Insert images
 <img src = …>
- A simple webpage:
Extensible Markup Language (XML)
XML: A language for constructing markup languages for similar to HTML
A descendant of SGML
Opens door to a World Wide Semantic Web
4. Internet Protocols
Internet Software Layers
Application: Constructs message with address
Transport: Chops message into packets
Network: Handles routing through the Internet
Link: Handles actual transmission of packets
TCP/IP Protocol Suite
Transport Layer
Transmission Control Protocol (TCP): More ‘reliable’ but less efficient
User Datagram Protocol (UDP): More ‘efficient’ but less ‘reliable’
Network Layer
Internet Protocol: IPv4, IPv5
5. Security
a. Attack:
o Malware (viruses, worms, Trojan horses, spyware, phishing software)
o Deniel of service (DoS)
o Spam
b. Protection:
o Firewalls
o Spam Filters
o Proxy Servers
o Antivirus software
Encryption
HTTPS and SSL
Public – Key Encryption:
Public Key: Used to encrypt messages
Private Key: Used to decrypt messages
Certificates and Digital Signatures
OPERATING SYSTEM
1. Operating System
Roles: Application Software: solve real-world problems
System software: manage a computer system and interact with Hardware
Operating system: System software that manages computer resources and provides and
interface for system interaction.
Software Classification:
Software : Application
System: Unity
Operating System: User Interface + Kernel
Operating System Components
User Interface: Communicates with users
Text based (Shell) (Bourne shell, Bash shell, C shell, Korn shell)
Graphical User Interface (GUI) (GNOME, KDE, Unity)
Kernel : Performs baic function: File manager, Device drivers, Memory manager, Scheduler and
dispatcher.
Memory, Process and CPU Management
Multiprogramming: The technique of keeping multiple programs in main memory at the same
time, competing for the CPU
Memory management: The act of keeping track of how and where programs are loaded in main
memory.
Process: The dynamic representation of a program during execution
Process management: The act of keeping track of information for active process
CPU scheduling: The act of determining which process in memory is given access to the CPU so
that it may execute.
2. Memory Management
Logical Address: A reference to a stored value relative to the program making the reference
Physical Address: An actual address in the main memory device.
Process Management – Process states
 In the new state, a process is being created.
 A process that has no barries to its execution is in the ready state.
 A process in the running state is currently being executed by the CPU. Its instructions are
being processed in the fetch – execute cycle.
 A process in the waiting state is currently waiting for resources (other than the CPU)
 A process in the terminated state has completed its execution and is no longer active.
CPU Scheduling: The act of determining which process in the ready state should be moved
to the running state.
First Come, First Served (FCFS): non-preemptive
Shortest Job Next: Non- preemptive
Round Robin: time slice, preemptive scheduling.
2. File System Directory
File System:
Main memory is where active programs and data are held while in use. A volatile
memory.
Secondary memory is nonvolatile – the date stored on it is maintained even when power
is not on.
File: Collection of data, used for organizing secondary memory.
File system: The operating system ‘s logical view of the files it manage
Directory: A named group of files.
Directory Trees
Directory tree: A structure showing the nested directory organization of the file system
Root directory: The topmost directory, in which all others are contained.
Path name: absolute vs relative
File Operation:
myFile = open(“new.txt”, “w+”): Open
myFile.close() : Close
import os
os.remove(‘….’) : Delete
os.rename(‘..’,’…’)
Application Layer
1. Information Systems
Managing Information:
Information system: Software that helps the user organize and analyze date
Three most popular applications of information systems: Electronic spreadsheets,
Database management systems, E-commerce
Spreadsheets: A program that allows the user to organize and analyze data using a grid of
cells
Cell: An element of a spreadsheet that can contain data or a formula
Spreadsheet Formulas: A computation provided by the spreadsheet software that can be
incorporated into formulas
Spreadsheet Analysis: Track sales, Analyze sport statistic, Maintain student grades, Keep a
car maintenance log, Record and summarize travel expenses, Track project activites and
schedules, Plan stock purchases.
Database Management Systems:
Database: A structured set of data
Database Management System (DBMS): A combination of software and data made up of
Physical database: Collection of files that contain the data.
Database engine: a software that supports access to and modification of the data
contents.
Database schema: a specification of the logical structure of the date stored in the
database.
Relational – Model DBMS:
Relational model: A database model in which data and the relationships among them are
organized into tables
Table: A collection of database records
Record (or object, or entity): A collection of related fields that make
up a single database entry (rows)
Field (or attribute): A single value in a database record (columns)
Each movie record has: a MovieId,a Title, a Genre, and a Rating
Key field: One or more fields of a database record that uniquely identifies it among all other
records in the table, e.g., MovieId.
Schema: Movie (MovieId:key,Title, Genre, Rating)
Structured Query Language (SQL):
A comprehensive relational database language for data management and queries
2. Artificial intelligence
3. Simulation, graphics, gaming and other applications.
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