Chapter 3 Internet Architecture

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Chapter 3Internet Architecture
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Overview

• What is a Network?
• IP Addresses
• Networks
• Information Transfer
• Cable Types
• Key Components of a Network
• Factors in Designing a Network
• Network Management System

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Introduction

• Building block of e-commerce is technology of
  www, protocols, standards, browsers, and servers
  
• Internet is a network of networks
• Network any to any communication between
  destinations (nodes) with unique address
• Node station or component linked as part of a
  network
• Intermediary nodes (normally special computers)
  forward traffic between network segments. These
  include routers and switches.

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Introduction

• Any computer of any size attached to the Internet
  is a host- servers as well as PCs.
• Each host has an assigned number to identify it
  to other hosts.
• This number is called IP address

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What is a Network?

• A connection between at least two computers for
  the purpose of sharing resources
• ALL networks are based on the concept of sharing
• Types
• Local Area Networks (LANs)
• Wide Area Networks (WANs)
• Metropolitan Area Networks (MANs)

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• Local Area Network (LAN)
• A clustered of networked computers
• Within a department, company or an office

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• Wide Area Network (WAN)
• Communication between network using third-party
  carrier to transmit between networks
• connects a company network a cross global
• Cover large geographical area

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• Metropolitan Area Network (MAN)
• Network in a specific geographic region
• Like city or county

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• LANs, WANs, and MANs can be
• Peer to peer networks
• Client/Server network

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Peer-to-Peer Network

• The linking of several PCs so that each acts as a
  peer, sharing and exchanging information without
  need for a centralized server
• Computers linked together as equals
• No centralized control
• Share resources on the same network in any way
  and any time
• Users are network administrator in its own
  computer
• lt 10 computers

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Peer-to-Peer Network
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Peer-to-Peer Network (Contd)

• Benefits
• Easy to install/configure
• Inexpensive
• User is able to control their own resources
• Independent from a dedicated server
• No need for a network administrator

• Drawbacks
• Security problems
• Performance suffers when a computer is accessed
• Difficult to have backup
• Decentralized logon passwords
• No centralized data management
• Status of information

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Client/Server Network

• Server
• Special purpose computer or specialized hardware
  and software designed for one function
• designed to address a clients request
• All programs or applications reside on the server
  
• Client any computer or workstation connected to
  a server within a network
• A cluster of computers (called clients) connected
  to one or more servers to form a network
• Allow authorized user to access any
  programs/application resided on the server

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Client/Server Network
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Client/Server Network

• All programs or application reside on the server
• Ex client send a request to use Word, the server
  allow client to download the executable portion
  of the word, when the work is finished, the
  program is uploaded onto the server for storage
  and future use
• Multi-user environment more than one authorized
  user can access any program or application that
  resides on the server

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Client/Server Network

• each computer or process on the network is either
  a client or a server
• Properties of a server
• Passive (Slave)
• Waiting for requests
• On requests serves them and send a reply
• Properties of a client
• Active (Master)
• Sending requests
• Waits until reply arrives

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Client/Server Network (Contd)

• Benefits
• Centralized security control
• Simpler network administration than peer-to-peer
  network
• Centralized password
• More scalable
• Ideal for computers are apart

• Drawbacks
• Network failure - clients are helpless
• Specialized staff are needed
• Higher costs

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IP Address

• An identifier for a computer or device on a
  TCP/IP network. Networks using the TCP/IP
  protocol route messages based on the IP address
  of the destination
• The format of an IP address is a 32-bits numeric
  address written as four numbers separated by
  periods.
• Each number can be zero to 255
• For example, 1.160.10.240 could be an IP address.
  

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IP Address

• A host number that identifies itself to other
  hosts
• Consists of strings of 32 bits
• E.g. 10111111010101010100000000001100
  191.170.64.12
• Host name Internet address consisting of text
  labels separated by dots
• Host Name
• Human-friendly internet addresses

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• Host number is divided into two parts
• Network part
• Represent organization unique IP address
• Local (node) part
• Assign by organization to computer within its Any
  organization is assign X.X.0.0
• X . X . Y . Z
• network node part
• part host

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• In order to specify a network with an IP address
  the node section is set to all 0's for example
  150.215.0.0 specifies the network for the above
  address.
• When the node section is set to all ones it
  specifies a broadcast that is sent to all hosts
  on a network. 150.215.255.255 specifies a
  broadcast address.

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Networks

• Networks are classified by three sizes

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IP Address

• There are 3 different address classes. The first
  byte determines the class of the address.
• Class A addresses start with 0.
• Class B addresses start with 10.
• Class C addresses start with 110.
• Classes can also be distinguished in decimal
  notation.
• 1 and 126 it is a Class A address.
• 128 and 191 it is a Class B address
• 192 and 223 it is a Class C address
• 127 is reserved for loopback and is used for
  internal testing on the local machine.

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IP Address

• Class D networks
• Class D addresses begin with 1110
• Used for multicasting
• Unlike unicasting where the packet goes to only
  one host IP address
• In this packet is broadcast to all the hosts on
  the subnet

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Zones and Domain name

• Zone name
• The last (right-most) part of a domain name
  preceded by a dot. It specify type of domain name
• Domain name
• A web address that contain two or more word
  groups separated by periods

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Networks (Contd)

• Zone
• Three-letter kind (com, gov, edu)
• Two-letter kind (ca, uk, jp)
• New general-purpose zones (firm, store)
• Last (rightmost) part of a domain name preceded
  by a dot

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Information Transfer

• In the internet all data sent through the
  internet is sent as Packets
• Packet is a sequence of bits that carries
  identifying information for transmitting the data
  as the data itself
• Packet consist of
• Header
• Data
• Typical size 100-2000 bytes
• Messages that are larger than packet size are
  split into a series of packets

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Information Transfer

• Packet
• Grouping of data for transmission on a network
• Large messages are split into a series of packets
  for transmission
• Protocol
• A rule governing how communication should be
  conducted between two parties, two computers, or
  a sources and a destination
• Pieces of software that run on every node or
  computer
• Internet Protocol (IP)
• Set of rules used to pass packets from one host
  to another

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Information Transfer (Contd)

• Internet Protocol (OSI)
• Open Systems Interconnection (OSI)
• Created by (ISO) in1978
• Seven layers model define basic network function
• A layered approach to networking
• Each layer handles a different portion of the
  communication process
• All People Seem To Need Data Processing
• Any Person Studying This Needs Desperate
  Psychotherapy

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OSI Reference Model
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OSI Reference Model (Contd)

• 1- Application Layer
• Defines requests and response formats
• Specify how two application program should
  communicate
• Standard HTTP
• Governs requests and response between browser and
  Web server application program
• Other standards SMTP
• HTML-compatible
• File Transfer Protocol (FTP), Simple Network
  Management Protocol (SNMP), Domain Name Service
  (DNS)
• SNMP protocol that control network devices at
  the application layers

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OSI Reference Model (Contd)

• 1- Application Layer
• Where the user begin to do something useful
• Send email
• Transfer a file
• Browse web site
• Domain name service (DNS)
• TCP/IP protocol
• Software that convert IP address into easy to
  remember names for users

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OSI Reference Model (Contd)

• 2- Presentation Layer
• AQ? what do the data look like
• Converts data into a format the receiving
  application can understand
• Called network translator

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OSI Reference Model (Contd)

• 3- Session Layer
• AQ? who is my partner
• Exchanges data for the duration of session
• Keeps track of the status of exchange
• Ensures only designated parties are allowed to
  participate in the session
• Enforces security protocols for controlling
  access

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OSI Reference Model (Contd)

• 4- Transport Layer
• AQ? where is my partner
• Manages the transmission of data across a network
• Ensure that two hosts receive and send
  information accurately.
• Transmission Control Protocol (TCP)
• Specifies how two host computers will work
  together
• Flow control
• Sequence assurance
• Reliability and integrity
• Allow 2 computers to communicate, regardless of
  being made of different vendor

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OSI Reference Model (Contd)

• 5- Internet Layer (network)
• AQ? which route do I use to get there
• Routes messages across multiple nodes for
  delivery
• Handles network congestion to minimize
  performance problems
• Internet Protocol (IP)
• Standard for routing packets

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OSI Reference Model (Contd)

• 5- Internet Layer
• At this layer the message is splits into packets
• Standard for routing packet is IP
• If the packets get lost they are resent
  automatically .

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OSI Reference Model (Contd)

• 6- Data Link Layer
• It deal with actual transfer of data between two
  computers located on the same network
• Packages data into frames for delivery
• Message at DLL is called data frames
• Point-to-point (PPP)
• Framing mark boundary between packets
• Error detection
• Ethernet

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OSI Reference Model (Contd)

• 7- Physical Layer
• Converts bits into signals for outgoing messages
  and signals into bits for incoming messages

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Cable Types

• Twisted-Pair Cable
• Unshielded Twisted Pair (UTP)
• Shielded Twisted Pair (STP)
• Optical Fiber
• Coaxial Cable
• Wireless Technology

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Twisted-Pair Cable

• Consists of two pairs of insulated copper wires
  twisted around each other
• Data transfer rate up to 100mbps
• Advantages
• Protect against cross talk and interference
• Easy to add computers to network
• Well understood technology
• Less expensive
• Disadvantages
• Susceptibility to noise
• Least secure
• Distance limitations
• Requires more expensive hubs

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Unshielded Twisted Pair (UTP)

• Pair of wires do not have the shielding against
  electrical interference
• Advantages
• Less expensive
• Easy to install
• Disadvantages
• Vulnerable to electromagnetic interference and
  crosstalk
• Subject to attenuation

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Shielded Twisted Pair (STP)

• An electrically grounded woven copper mesh
  wrapped around each twisted pair
• Advantage
• Reduces electromagnetic interference (EMI)
• Disadvantage
• Makes the wiring thick and is difficult to
  maintain

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Optical Fiber

• Uses light rather than voltage to indicate one
  and zeros
• Data transfer rate up to 2 Gbps
• Advantages
• High speed transmission
• High security
• Smallest in size
• Supports voice and video data
• Disadvantages
• Expensive
• Difficult to install
• Require two cables to transmit receive data
• Require special connections

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Coaxial Cable

• Copper center shielded by a plastic insulating
  material
• Advantages
• Transmits up to 10Mbps over 500m
• Easy to install
• Low maintenance
• Good resistance to noise over long distances
• Disadvantages
• Inflexible
• Low security
• Limited distance

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Wireless Technology

• Data transmission without physical attachments
• Microwave
• Connect LANs in separate buildings
• Radio waves
• No distance limitations
• Susceptible to atmospheric and electronic
  interference
• Subject to government regulations
• Infrared transmissions
• Interference from bright light

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Key Components of A Network

• Network Interface Card (NIC)
• Modem
• Hubs and Switches
• Routers
• Gateways

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Network Interface Card (NIC)

• A card installed in a slot in a computer to allow
  communication between the Pc and other PCs in the
  LAN .
• Installed in a slot with a cable plugged into the
  back
• Plugged into a wall jack connection or into the
  hub/switch directly

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Network Interface Card

• Modem
• To communicate over telephone line
• Converts digital signals into analog form for
  transmission and incoming analog signals into
  digital signal across the telephone line

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Hubs

• Hub
• A piece of hardware
• Operates at Physical Layer
• Acts as a connecting point
• 3 types of hubs
• Passive require no power ,
• Active require power to strengthen signals
• intelligent hubs

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Hubs and Switches

• Switch
• Offers direct connection to a particular PC
• no traffic congestion
• Available for almost every OSI level

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Routers

• Pieces of hardware
• Operate at Internet Layer
• Linking network to other network
• Evaluate network traffic and stop local traffic
  from causing congestion
• Filter out packets that need not be received
• Expensive and difficult to operate
• Can select alternative path for packet

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Gateways

• Special-purpose computer allowing communications
  between dissimilar systems on the network
• Operate at Application Layer primarily
• Difficult to install and configure
• Expensive

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Factors in Designing a Network

• Location
• Capacity
• Distance limitations
• Cost
• Potential growth
• Security

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Factors in Selecting Network Architecture

• Hardware requirements
• Software requirements
• Disaster recovery and fault-tolerance
  requirements
• Corporate culture and organizational factors

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Network Management System

• Manager
• Monitor various parts of the network
• Management protocol (SNMP)
• Managed Nodes
• Objects
• Management Information Base (MIB)
• Software that defines the objects that can exist
  based in the initial design of network
• Requests and responses

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Large-Scale E-commerce Issues

• Financial exposure
• IP exposure
• The ease in identifying IP addresses increases
  network computers vulnerability to hacking
• Legal security
• Companies are responsible for providing security
  for the protection information
• Packet sniffing
• Outsider use program to steal information
  traveling through a company network

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Ensuring Corporate and Information Security

• Firewalls
• Serves as intermediary between an internal
  network and internet
• Control which packets can be pass to network
• Proxy firewalls
• IP Security
• Packet filtering
• Intrusion detection systems
• Serves as a watch dog for unauthorized activates

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Chapter 3Internet Architecture