module 01 - introduction to network security

7/30/2019 Module 01 - Introduction to Network Security

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Network SecurityAdministrator

Module I:

Introduction to NetworkSecurity


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All Rights reserved. Reproduction is strictly prohibited

Module Objectives

~ Introduction to NetworkTopologies

~ Types of Networks

~ OSI Model

~ Networking Devices

~ Transmission Modes


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Module Flow

Network Topology Types of network

OSI ModelNetworking Devices

Transmission Modes


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Network Topology: Star

~ All devices are connected to a controller located centrallycalled hub as a point-to-point connection

~ The devices communicate with each other through thecentral hub




Network Topology: Bus

~A multi-point design consisting of a long cablecalled bus that connects all devices

~All devices are connected to the bus usingconnections like drop lines and tabs




Network Topology: Ring

~All devices have a point-to-point connection withdevices located on both sides

~ Communication between the devices isunidirectional




Network Topology: Mesh

~ Every device has a point-to-point connection withevery other devices

~ Unidirectional communication exists betweenany two devices




Network Topology: Tree

~ Majority of devices are connected to a controller locatedcentrally called hub

~ Other devices are connected to a derivative of the hubcalled a secondary hub

hubhub

hub

hub




Network Type: LAN

~ Features

Extends over a small area within a kilometer

Connects workstations and PCs of private property~ Design

Shares information between PCs or workstations

~ Technologies of LAN

Ethernet

Token Ring

FDDI (Fiber Distributed Data Interface)


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Network Type: LAN

Single Building LAN


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Network Type: WAN

~ Features

WAN facilitates communication over vast physical areas usingpublic, leased or private devices

Length of a WAN can extend over some miles

~ Technologies of WAN

Packet Switched WANs

ATM

B-ISDN (Broadband ISDN)


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Network Type: WAN


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Network Type: MAN

~ Features

MAN provides communication for physical areas such as an entirecity

Wireless infrastructure is used in a MAN communication

MAN can be owned by a private organization or a facility of apublic organization

~ Technologies of MAN

Ethernet based MANs (Metro Ethernet)

DQDB (Distributed Queue Dual Bus)

SMDS (Switched Multi-megabit Data Services)


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Network Type: MAN


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OSI Model

Host A

Application Layer

Presentation Layer

Transport Layer

Network Layer

Data Link Layer

Session Layer

Physical Layer

Host B

Application Layer

Presentation Layer

Transport Layer

Network Layer

Data Link Layer

Session Layer

Physical Layer

Messages

Packets/Data gram

Frames/Cells

Frames/Cells

Segments

Messages

Messages


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Physical Layer

~ First layer of the OSI model

~ Responsibilities

Communicating data streams over physical medium

Mechanical and electrical requirements of

transmission media Organization of bits of data

Data encoding


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Physical Layer


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Data Link Layer

~ Second layer of the OSI model

~ Responsibilities

Physical layer security

Segregation of data into frames

Transmission control Fault control

Access control


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Data Link Layer


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Network Layer

~ Third layer of the OSI model

~ Responsibilities

Source to destination delivery of data packets

The global addressing of the data packets

Routing data packets to final destination Network traffic control

Fault handling

k


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Network Layer


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Transport Layer

~ Fourth layer of the OSI model

~ Responsibilities

Addressing using service points

Segregation and Re-gathering

Link control Transmission control

Fault handling

T L


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Transport Layer

S i L


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Session Layer

~ Fifth layer of the OSI model

~ Responsibilities

Establishing communication between processes

Organization of data using check points

S i L


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Session Layer

P t ti L


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Presentation Layer

~ Sixth layer of the OSI model

~ Responsibilities

Deals with syntax and semantics of data exchange

Encryption of data for security

Data compression to reduce rate of data transmission

P t ti L


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Presentation Layer

Application La er


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Application Layer

~ Seventh layer of OSI model

~ Responsibilities

Permits users access to the network

Provides mail services

Provides directory services Provides network virtual terminal services for

communicating with remote hosts

Application Layer


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Application Layer

Network Device: Repeater


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~ Electronic device that extends physical lengthof network

Function: Restores the signals before theybecome weak

Operates in OSI model at:

Physical layer

~ Advantages Links segments of network of different

medium

~ Disadvantages

Improper monitoring compromises entirenetwork

Enhances traffic on the segments

No traffic segregation



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N t k D i M lti l


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Network Device: Multiplexer

~ Device that merges multiple electric signals into a single signal

~ Function

Combines several inputs into a single output Combines digital and analog signals



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~Advantages

Multiplexer allows several digital signals to be

transmitted using a single physical channel

~ Disadvantages

Denial-of-Service weakness is present in someMultiplexer

Two streams of data competing for a single channelcause delay in transmission

Network Device: Routers


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~ Hardware device that determinesthe best path for data transmission

~ Function Sends packets across several

interconnected networks

~ Operates in OSI model at

Physical layer Data link layer

Network layer

~ Types Backbone routers

Broadband Routers

IP Routers

Remote Access Routers



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~Advantages

Routers can link diversemedia such as LAN, WANand can transmit data

Routers avoid datacollisions duringtransmission

~ Disadvantages

The sent packets cannot besort out causing additional

transmission that increasescost

Routers do not haverestricted access controls

Network Device: Brouter


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Network Device: Brouter

~ Device that works as router and bridge

~ Operates like a bridge and forwards the data tothe next segment

~ Functions

Routes TCP/IP packets Bridges data it cannot route

~Advantages

Uses physical address Used for mixed-protocol traffic

Network Device: Hub


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Network Device: Hub

~ Device to connect devices in a network

Function: Groups devices into a single network segment

Performance: Provides optimized and preset remote IP servicesto medium sized networks

~ Types

Passive Hub

Active Hub

Network Device: Hub


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Network Device: Hub

~Advantages

Computers and broadbandmodems connect to the

network through the Hub Prevents network crashes

Allows mixing of slow (10Mb/sec) and fast (100Mb/sec) Ethernet devices

~ Disadvantage

Computers that areconnected to isolated

hubs, are isolated from thenetwork

Network Device: Switch


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Network Device: Switch

~ Device which directsincoming data to a singleoutput port from numberof input ports

~ Function Directs data flow through

specific path

Forwards data using MAC

address embedded ineach data packet

~ Advantages andDisadvantages

Works efficiently thanHub

Packet sniffing is possible

Network Device: Bridge


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Netwo ev ce: dge

~ Logical devices that segments LANs to decrease the trafficflow in the network

~ Function Segregates traffic by dividing the network into segments

~ Operates in OSI Model at Physical layer

Data link layer

Bridg e


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Network Device: Modem


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~ Device that acts as both modulatorand demodulator

~ Function: Provides serial communication

capabilities across phone lines

~ Speed of modem depends on thespeed of Universal AsynchronousReceiver/Transmitter (UART) chipin the Computer

~ Disadvantage: Transmission of data is slow

Network Device: Cables


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~ Wires that connect network devices with eachother across the network

~ Function

Transfers raw data between networkdevices

~ Types of cable

Twisted pair Coaxial

Optical fiber

~ Advantages and Disadvantages

Less problems with networking during badweather

To take backup, there is a necessity of

extra cables makes it expensive

Network Device: ISDN Terminal Adapter


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p

~ Interfacing device

~ Function

Translates the signal between twodigital adapters

~ Advantages

Allows non-ISDN terminal atphysical layer to communicate withISDN network

Available as add-in expansion cardswhich are installed into computers

Network Device: Network Card


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~ Device that joins computers inLANs

~ Function Enables systems to connect to the

network

Provides connectivity between nodes~ Advantages

Used in server clusters

NICs need not be fixed with physicalcable

Used to both send and receive data

Data Transmission Modes


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~Half -Duplex:

Data is transmitted in LANsonly one direction at a time

Broadband networksupports half-duplexcommunication

~ Full- Duplex:

Data is transmitted inLANs simultaneously in

both directions

Using suitable equipmentfull duplex communicationcan be obtained in some

LANs and Ethernet

Broadband and Baseband


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~ Broadband

Used in LANs

Transmits single signal through single cablesimultaneously

Data transmitted is divided into distinct units called

frames

~ Baseband

Used in WANs

Transmits multiple signals through a single cablesimultaneously

Segments and Backbone


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~ Segments

LANs comprising of networkedterminals and user equipment

Used for large organization networks

~ Backbones

Collection of LANs thatanother LAN called Backbone

Acts like a channel fbetween segments

are are interconnected to

acilitating communication

Client/Server and Peer-to-Peer Networking


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~ Client/Server Network In a network, some

computers function asclients and some asservers

Client:

A computer that gains fromthe services provided byserver

Server:

A computer that offers

services to a client

~ Peer-to-Peer Network

Individual computers

function as both clientsand servers

Confined to small groupsof computers and networks

smaller than single LANs

Summary


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~ Network Topology is the arrangement of networkdevices

~ Different types of topologies are Star Topology,BusTopology,Ring Topology,Mesh Topology,Tree Topology

~ The different types of networks are LAN,MAN,WAN

~

OSI model covers all the features of networkcommunications

~ Networking devices are used for sharing the data orresources in a network

~ Transmission mode is the path of the signal flowbetween two connected devices.It can of types Half-Duplex and Full- Duplex

module 01 - introduction to network security

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