networking basics

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Covers a small area Connects computers and workstations covering a

local area like, office or home

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Advantages of LAN: Improves productivity due to faster work Provides easy maintenance New systems can be installed and configured

easily Disadvantages of LAN:

Limited number of systems can only be connected Cannot cover large area Network performance degrades as number of

users exceeds

LAN Types

Ethernet Token Ring Token Bus FDDI

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LANs are classified depending on the techniques used for data sharing

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Made up of multiple LANs within limited area Connects different LANs in a campus

Interconnects networks within a city Supports data and voice transmission

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Covers a wide geographical area which includes multiple computers or LANs e.g. Internet

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Consists of two elements, Client and Server Server:

A centralized element which provides resources to client

Manages data, printers or network traffic Client:

Manages local resources used by users such as monitor, keyboard, CPU and peripherals

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Also known as ISO-OSI Reference Model Developed by International Organization for

Standardization (ISO) Describes flow of information from one computer to

another Consists of seven layers

Topology refers to physical or logical arrangement of network

Physical topologies are◦ Single Node◦ Bus◦ Star◦ Ring◦ Mesh◦ Tree◦ Hybrid

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Single device, at times device called dumb terminal is connected to the server

Devices operates on files from server and returns them back after completing task

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Disadvantages:◦ Network consists of

single device

◦ Dumb terminal is dependent on server

Advantages:◦ Easy to install,

configure and manage

◦ Least expensive

◦ Single cable is required

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All devices are connected to a common cable called trunk

Maximum segment length of cable is 200 m Maximum of 30 devices per segment

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Server is at one end and devices are at different positions

50 ohm terminator is used Devices are not responsible for data

transmission Number of collisions are more Usually uses Thinnet or Thicknet Performance degrades as more computers

are added to the bus.

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Advantages:◦ Installation of

devices is easy

◦ Requires less cable compared to star topology

◦ Less expensive and works better for smaller networks

Disadvantages:◦ If backbone breaks,

entire network gets down

◦ Difficult to isolate problems

◦ Limited number of devices

Each device is connected to a central device called hub through cable Data passes through hub before reaching destination If a computer goes down, the network

functions normally.

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Advantages:◦ Easy to install,

configure, manage and expand

◦ Centralized management

◦ Addition or removal of device does not affect the whole network

Disadvantages:◦ Requires more cable

◦ Failure of hub affects entire network

◦ More Expensive

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Devices are connected in a closed loop

All devices have equal access to media

Most common type is Token Ring

Each computer acts as a repeater and keeps the signal strong

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Advantages:

◦ Data travels at greater speed

◦ No collisions

◦ Handles large volume of traffic

Disadvantages:

◦ More cabling is required compared to bus

◦ One faulty device affects the entire network

◦ Addition of devices affect network

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Consists of two independent primary and secondary rings

Secondary ring is redundant, used only when primary stops functioning

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Used in WANs to interconnect LANs

Every device is connected to every other device

Use routers to determine the best path of communication

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Full mesh topology – All devices are connected to each other

Partial mesh topology - Some devices are connected to only those with whom they exchange most of the data

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Types

Full mesh Partial mesh

Advantages:

◦ Improves fault tolerance

◦ Failure of one link does not affect entire network

◦ Centralized management is not required

Disadvantages:

◦ Difficult to install and manage

◦ Each link from one device to other requires individual NIC

◦ Very much expensive

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Connects groups of star networks

Devices are wired to root hub

Root hub is connected to second level devices

Lowest level devices are smaller computers

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Advantages:◦ Easy to add new

devices◦ Point-to-point wiring

for each device◦ Fault detection is

easy

Disadvantages:◦ Difficult to configure◦ If backbone breaks,

entire network goes down

◦ More expensive

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Combines two or more different physical topologies

Commonly Star-Bus or Star-Ring Star-Ring uses Multistation Access Unit (MAU)

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Advantages:

◦ Used for creating larger networks

◦ Handles large volume of traffic

◦ Fault detection is easy

Disadvantages:

◦ Installation and configuration is difficult

◦ More expensive than other topologies

◦ More cabling is required

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Segment Length – Length of single wire Attenuation – Indicates loss of signal Bandwidth – Amount of data carried by cable Number of Segments – Maximum number of

segments in network Cost – Copper cables are cheapest, fiber optic

cables are expensive Interference susceptibility and crosstalk –

Defines concept of electronic interference on cables

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Copper medium is the cheapest mode of data transfer

Types of cables

Coaxial cable Twisted pair cables

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Consist of a solid copper core surrounded by an insulator mainly made up of Poly Vinyl Chloride (PVC) or Teflon

Coaxial cables are less prone to interference (both internal and external)

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Coaxial cables are mainly divided into four categories

Types of Coaxial cables

RG58 RG8 RG6 RG59

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Maximum segment length is 200 (185) meters

Interference protection is better than twisted pair cables

BNC-T connector is used to connect this cable Used in thinnet (10BASE2) network Mostly used in changing environments

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Maximum segment length is 500 meters Interference protection is good compared to

any copper cable BNC-T or Vampire Tap connector is used to

connect this cable Used in 10BASE5 network

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Broadband quad-shielded cable

Provides lower attenuation characteristics

Useful in cable TV, CCTV and satellite dish antenna

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Solid conductor is surrounded by a foam polyethylene dielectric

Useful in security camera, cable TV and home theatre

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A pair of cables twisted around each other forms a twisted pair cable.

Twisted Pair cables

Unshielded Twisted Pair

Shielded Twisted pair

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Pair of unshielded wires wound around each other

Easily gets affected by EMI, RFI and crosstalk

Maximum segment length is 100 meters

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Cat 7

Cat 6

Cat 5eCat 5

Cat 4

Cat 3

Cat 2Cat 1

UTP

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Pair of wires wound around each other is placed inside shield

Better protection from EMI, RFI and crosstalk as compared to UTP

Maximum segment length of 100 meters

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Consists of centre glass core surrounded by cladding

Electrical signals are converted into light signals

LED or laser is used to transmit signal

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Bandwidth – Carries large amount of data ranging from 100 Mbps to 1 Gbps

Segment Length – Transmits data signals over larger distance

Interference – No electric signals pass through these types of cables thus providing security

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Fiber optic cables can carry signals in a single direction.

Fiber Optic Cable Types

Single Mode Multi mode

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A type of cable that has only a single strand of glass fiber with a thin diameter.

Fiber optic cables that use lasers are known as single mode cable.

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A type of cable that contains a glass fiber with a larger diameter.

It is a 62.5/125 micrometer fiber cable.

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Straight Tip (ST) – Joins individual fibers to optical devices

Subscriber Connector (SC) – Attaches two fibers to send and receive signals

Medium Interface Connector (MIC) – Joins fiber to FDDI controller

Sub Miniature Type A (SMA) – Uses individual connectors for each fiber stand

Fiber Jack – Attaches two fibers in snap lock connector

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Characteristics UTP STP Coaxial Cables Fiber Optic Cables

Bandwidth 10 Mbps – 100 Mbps

10 Mbps – 100 Mbps

10 Mbps 100 Mbps - 1 Gbps

Maximum cable segment

100 meters 100 meters 200 – 500 meters 2 k.m. – 100 k.m.

Interference rating Poor Better than UTP Better than twisted pair wires

Very good as compared to any other cable

Installation cost Cheap Costly than UTP Costly than twisted pair wires

Most costly to install

Bend radius 360 degrees / feet 360 degrees / feet 360 degrees / feet or 30 degrees / feet

30 degrees / feet

Security Low Low Low High

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Networking devices interconnects networks Manage data flow and network traffic

NetworkingDevices

Repeaters Hubs Bridges Switches Routers Gateways Other Devices

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Operate at Physical Layer of the OSI model

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Reshape the weak signal Connect two segments of the same LAN

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Simplest and low cost device Also known as Multi-port Repeater Operate at Physical Layer like Repeater Data transfer to all the ports Hub types:

Active hub – Provides signal regeneration Passive hub – No signal regeneration Intelligent hub – Provides management of each port

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Layer 2 devices as works at Data Link Layer of the OSI model

Interconnect multiple LANs and manages data flow

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Working of a bridge

Capable of passing a frame Check Physical address Pass frame to the specified segment Perform error checking on the frame

Bridges

Transparent Bridge

Translational Bridge

Source-route Bridge

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Features◦ Easy to use as just plug in device ◦ Helps in network expansion◦ Divides large network into small segments◦ Used for increasing network reliabilityDisadvantages◦ Frames are buffered so provides network delay ◦ During high traffic may overload network◦ Does not filter broadcast packets◦ Expensive than Repeaters

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SwitchingMethods

Cut-throughMethod

Store & ForwardMethod

Fragment-FreeMethod

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Provide signal flow management Replace slower hub Being a Data Link Layer device uses MAC address

for data transfer Data transfer to specific port

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Operate at Network Layer of the OSI model Can connect nearer or far network segments

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Decide the best route with the help of network layer address

Responsible for Source to Destination delivery of packet

Route types: Static route – Routing tables are manually configured Dynamic route – Routing tables are automatically

configured

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Helps routers to learn network topology and network changes

Routing algorithms are used by routing protocols for deciding the path

GatewayTypes

AddressGateway

ProtocolGateway

ApplicationGateway

TransportGateway

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Operate at all layers of the OSI model Act as gate to other networks A default gateway is on the same subnet as your

computer

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Address Gateway – Interconnects same protocol networks

Protocol Gateway – Interconnects different protocol networks

Application Gateway – Connects two parts of applications

Transport Gateway – Connects networks at transport layer

OtherDevices

Multi-ProtocolRouters Brouters Layer 3

Switches

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Multi-protocol router supports multiple communication protocols

Like router, it operates at Network Layer

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Brouter provides combined functions of Bridge and Router

Works at two layers, Data Link and Network Can operate only as bridge or only as router High performance switch operating at network layer

is Layer 3 Switch

Set of predefined rules used by devices in network for data transfer

Network Protocols:◦ TCP/IP◦ ARP/RARP◦ ICMP/IGMP◦ UDP◦ IPX/SPX◦ HDLC/SDLC

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Two layer communication protocol used by Internet

TCP provides connection-oriented reliable transport service

Divides the message into smaller packets called segments

IP is a connectionless and unreliable datagram protocol and provides no error checking

IP transfers data in the form of packets called datagrams

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Designed before OSI model

Consists of five layers

Provides independent protocols at each layer

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To deliver packet both physical and logical addresses are necessary

Address Resolution Protocol (ARP) provides physical address when logical address is known

Reverse Address Resolution Protocol (RARP) maps logical address to physical address

RARP is useful when device is booted for first time

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Internet Control Message Protocol (ICMP) provides error reporting and query management mechanism

ICMP handles problems occurring while packet transmission

Internet Group Message Protocol (IGMP) manages multicasting and group membership of devices

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Error Reporting

Destination Unreachable

Router Solicitation and Advertisement

Timestamp request and reply

Address MaskRequest and reply

Echo request and reply

Query

Source Quench

Time Exceeded

Redirection

Parameter Problem

ICMP Messages

User Datagram Protocol (UDP) provides connectionless process-to-process communication

UDP packets are called user datagrams. User Datagram Format:

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Novell NetWare system uses IPX/SPX as communication protocol within networks

IPX (Internetwork Packet Exchange) operates at Network layer for connectionless communication

SPX (Sequenced Packet Exchange) operates at Transport layer for connection-oriented communication

Together, IPX/SPX provides same services as TCP/IP

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High Level Data Link Control (HDLC) and Synchronous Data Link Control (SDLC) are bit-oriented synchronous protocols in which data frames are interpreted as series of bits

Both are useful for half-duplex and full-duplex communication

Windows XP still support DLC

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OSI Layers Protocols

Physical Layer No protocols defined

Data Link Layer HDLC, SDLC

Network Layer NetBEUI, IP, ICMP, IGMP, ARP, RARP, IPX

Transport Layer NetBEUI, TCP, UDP, SPX

Session Layer NetBIOS, SAP, SMTP, FTP, DNS, SNMP,

Presentation Layer NCP, RIP, NLSP, SMTP, FTP, DNS, SNMP, NFS

Application Layer SMTP, DNS, SNMP, NFS, TFTP

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Specifies how mail should be delivered from one system to another

Standard protocol used for transferring email from one computer to another

Makes connection between sender’s server and recipient and then transfer messages

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A two-way transmission channel established between the sender SMTP and a receiver SMTP

Commands are generated by sender SMTP and sent to receiver SMTP

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Set of rules used to exchange files on World Wide Web

Users can exchange text, graphic images, sound, video and other multimedia files

Defines how messages are formatted and transmitted over the Internet

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HTTP works on request and response between browser and server

Web server is designated to handle HTTP requests then sends requested HTML page

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Proxy servers is used with firewalls to monitor and direct HTTP traffic through proxy to external internet

Used over Internet to exchange files Uses Internet's TCP/IP protocols to enable

data transfer Establishes two way connections between

computers

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File Transfer Protocol (FTP)

Machine that are involved in an FTP transaction – Client (local host) machine and a server (remote host)

Client machine initiates transfer Get command used to

copy files from server toclient

Put command is used tocopy files from client to server

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Used to transfer files to and from a remote computer

Used by servers to boot diskless workstations, X-terminals and routers

Start with a small amount of built-in software

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Connection and Communication between Client/Server ◦ Communication and messaging different in TFTP

when compared with FTP◦ TFTP uses UDP◦ Process of transferring a file:

Initial Connection Data Transfer Connection Termination

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Used to transfer Usenet news from one machine to another machine

Usenet news is a large collection of discussion groups, covering a wide range of topics

NNTP provides connection-oriented service Communication takes place between a client

and a server that keeps netnews on both the places

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Framework for managing devices over Internet using TCP/IP protocol suite

Provides set of fundamental operation for monitoring and maintaining devices in the network

Agent is server process that maintains Management Information Base (MIB) database for host

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Used to retrieve email from remote server to local client over TCP/IP connection

E-mail clients using POP3 connect, retrieve all messages or store them on user's PC as new messages or delete them from server and disconnect

POP3 is a TCP/IP client/server protocol Session States:

◦ Authorization State◦ Transaction State◦ Update State

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Enables the users to work with the mail on the server

Does not download the mails Used to access e-mails from a local server Working with mails

◦ Accessing and deleting mails◦ Attachments

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Advantages:◦ As the e-mail folders

are stored on the server, the user is able to read email from any computer which belongs to the network

◦ To access more than one account from different locations, IMAP will be the most efficiently

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Disadvantages: Complicated Results in higher server

loads than POP3 Utilizes a lot of server

resources

BOOTP – First automated configuration tool for IP hosts◦ Bootstrapping – Provides the host with the

capability of getting IP addresses while machine boots

◦ Requires two phases: Client provided with address and other parameters Client downloads softwares to function on network

and perform tasks

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Dynamic Host Configuration Protocol (DHCP) – Successor of BOOTP with different features

Dynamically assign addresses to clients and centrally manage

Consists of two major components – 1. Address allocation mechanism 2. Protocol that allows clients and server to communicate

DHCP standard includes three different address allocation mechanisms:◦ Manual , Automatic and Dynamic

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Network protocol used on internet or local area network connections

Terminal emulation program for TCP/IP networks

Enables to control server and communicate with other servers on network

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Telnet client – Software that acts as interface to user, processing user commands and presenting output from remote machine

Telnet server - Program running on remote computer that has been set up to allow remote session

Telnet runs over connection-oriented TCP TCP connection maintained for duration of

Telnet session Client and server send information at same

time over Telnet session because TCP is a full-duplex

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WWW is a network of Internet servers, which support documents that are developed using HTML

Hyper Text Markup Language (HTML) is a language in which these documents are formatted

Client-side◦ Computer application – Web browser that runs on

user’s local computer and connects to server◦ Interpreter that interprets code in an HTML page◦ Operations carried out on client-side

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Server Side ◦ Software program – Web server that runs on a

remote server◦ Manages and shares web based applications ◦ Operations include processing and storage of

data from client to server

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Wireless networking allows you to establish: Communication using standard network

protocols Communication without the use of

cables Technologies used for wireless access

based on Wireless fidelity (Wi-Fi) Home Radio Frequency

(HomeRF)

Peer-to-Peer(P2P) or Ad-Hoc◦ Connected wirelessly with the use of wireless

Network Interface Card (NIC)◦ Computers can access printers and share files◦ Wired LAN can be accessed using bridging

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Access point or Infrastructure wireless LAN◦ Wireless device connects

to the access point to connect to the network

◦ Access point acts as a hub to connect two wireless devices

◦ Wireless bridge used to connect wireless network to wired network

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Security◦ Four methods of wireless network security:

Data encryption - WEP (Wired Equivalent Privacy) and WPA (Wi-Fi Protected Access)

Port based access control Service Set Identifier (SSID) Media Access Control (MAC) address filtering

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The important components required for setting up a wireless network are:◦ Medium◦ Access point and Extension point◦ Wireless bridges and Power line bridges◦ Antennas◦ Wireless adapters◦ Wireless Station and Server◦ Software

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Wireless medium is an unguided form of networking medium

Wireless transmission involves use of technologies such as Bluetooth, Infrared, Lasers, Radio signals and Microwave technologies

Mobile computing allows users to do their work at any location

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Access Point◦ Device that bridges a wireless connection and

a wired connection ◦ Two types of access points: Hardware access

points and Software access points Extension Point

◦ Used if single access point is not able to cover entire area

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Hardware access point is a physical device that is used to establish a connection between a wired network and a wireless network

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Software Access Points are computer which includes a wireless network interface card.

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Extension points are used if a single access point is not able to cover the entire area.

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Antennas are used to increase the range of wireless network

Types of antennas used:◦ Omnidirectional antennas - Used indoors and

small in size◦ Directional antennas - High gain and used for

long range outdoor use Wireless adapters help to connect computer

or PDA to a network Wireless adapters are available as PC cards,

PCI and mini PCI, USB, and CompactFlash.

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Wireless Local Area Network consists of wireless station and wireless server

Wireless station - Connects wireless network into a wireless medium

Wireless Stations

Wireless Clients Access Points

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Wireless server – The main server which controls all devices within the wireless network

Wireless network adapter requires two types of software so as to function properly:◦ Driver◦ Configuration Utility

Windows XP has built-in tools for configuring network adapter settings

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networking basics

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