Computer networking (nnm)

COMPUTER NETWORKING

N. N. Maurya

NETWORKING OF COMPUTERS

What is computer network? Why we need a computer network ? How a computer network works ? Network models IP Addressing Network Topology Different type of network Requirements for network Applications Security

WHAT IS NETWORK ?

Interconnection of computers

How to interconnect ?

Links required for interconnecting „N‟ nodes

Suitable ?

Solution ?

GOALS OF THE NETWORKING

Resource Sharing

Information/Data Sharing

Centralized Computing

Remote Computing

Communication – Mail, Video Conferencing

Improving Security

Managing Tasks and Applications

THE PAST

THE PRESENT : CONVERGENCE

THE FUTURE : INTERNET AS PLATFORM

SOME BASICS

Why a computer network is required ? Data transfer

How to identify a node in network ? IP address

How data flows in networks ? Packet form

What is Packet switching ? Statistical Multiplexing

ReceiverSenderPacket

Transmission

SOME BASICS……..

Channel capacity = Maximum data rate for a channel Nyquist Theorem:

Bandwidth = W Data rate =< 2W

Bilevel encoding: Data rate = 2 X Bandwidth

Multilevel encoding: Data rate = 2 X Bandwidth X log 2 M

For example if M = 4, Capacity = 4 X Bandwidth Shannon‟s Theorem:

Maximum number of bits/sec = W log2 (1+S/N) For telephone line: S/N = 30 dB, W = 3K; Capacity =

30Kbps

TREND: TRAFFIC > CAPACITY

Expensive Bandwidth Cheap Bandwidth

Sharing No sharing

Multicast Unicast

Needs QoS QoS is not an issue

Wireless LAN Possible in LAN

NETWORK MODELS

Network modelsOSI

TCP/IP

Connection oriented protocol

Connectionless protocol

OSI REFERENCE MODEL

The seven layers

Each layer hides complexity of lower layer

Layering enforces modularity

End-to-end layer: top 4 OSI layers

Network layer: OSI network layer

Link layer: bottom 2 OSI layers

A-P-S-T are implemented in software

N-D-P are implemented in hardware

THE SEVEN LAYERS

THE SEVEN LAYERS ………….

Physical layer Transmission of bit stream over physical medium Coding scheme, connector shape and size, bit-level

synchronization

Data link layer Reliable transfer of information across the physical link Sends blocks - frames Medium access control (MAC): data link-layer address and access

to the medium Logical link control: link error control and flow control Ethernet card: physical and data link layers


Network layer Concatenate logically a set of links to form an end-to-

end link.

Compute a route

Segmentation and reassembly

Unique network-wide addresses : IP address

The beauty of IP is that we can layer it over any data link layer technology

Type-of-service in the IP


Transport layer Create the abstraction of an error-controlled,

and flow-controlled, end-to-end link

Multiplex multiple applications to the same end-to-end connection

Port number


Best-effort network layer- drops packets- delays packets- reorders packets- corrupts packet contents

Many applications want reliable transport- all packets reach receiver……in order they were sent- no data corrupted- “reliable byte stream”

Need a transport protocol, e.g., Internet‟s Transmission Control Protocol (TCP)

PRINCIPLES OF RELIABLE DATA TRANSFER

Important in application, transport, and link layers Top-10 list of important networking topics!

Sending Process

Receiving Process

Reliable Channel

Sending Process

Receiving Process

Unreliable Channel

RDT protocol

(sending side)RDT protocol

(receiving side)

Application Layer

Network Layer

Transport Layer

Characteristics of unreliable channel will determine complexity of reliable data transfer protocol


Session layer provides the control structure for communication between

applications The Internet does not have a standard session layer protocol.

Presentation layer deals with data encrypt data The Internet does not support a standard presentation layer.

Application layer Provides access to the users WWW: browser, server, navigation file transfer using TCP real-time audio and video retrieval using UDP

TCP/IP MODEL

TCP/IP protocol consists of four/five layers The lower layers correspond to the layer of the

OSI model. The application layer of the TCP/IP model

represents the three topmost layers of the OSI model

TCP/IP is based on two principles IP Over everything end to end

TCP/IP MODEL………..

TCP – Transmission Control Protocol IP – Internet Protocol (Routing)

TCP/IP Model TCP/IP Protocols OSI Ref Model

Physical

Datalink

Network

Transport

Session

Presentation

Application

Physical

Datalink

Network

Transport

Session

Presentation

Application

Host to

Network

Network

Transport

Application

Host to

Network

Network

Transport

Application

UDP

HTTPTelnet

Point

- to -

Point

Packet

RadioEthernet

IP

TCP

FTP

UDP

HTTPTelnet

Point

- to -

Point

Packet

RadioEthernet

IP

TCP

FTP

ADVANTAGE OF TCP/IP MODEL

Open Protocol Standards Independent of actual physical network &

Computer hardware or software. Run over Ethernet/ Token Ring/ Modems/ Unix/ Windows PCs

Uses Common Global address scheme (IP addressing) that enables global connectivity

IP ADDRESSING

IP addressing scheme is integral to the process of routing IP datagram through an internetwork.

Each IP address has specific component and follows a basic format.

These IP addresses can be subdivided and used to create addresses for sub networks.

Each host on a TCP/IP network is assigned a unique 32-bit logical address that is divided into two main parts: the network number and the host number.

The network number identifies a network and must be assigned by the internet Network Information Center (InterNIC) if the network is to be part of the internet.

IP ADDRESSING

An Internet Service Provider (ISP) can obtain blocks of network addresses from InterNIC and can itself assign address space as necessary.

The host number identifies a host on a network and is assigned by the local network administrator.

IP ADDRESSING

Class D and E are reserved for multicasting and research

IP ADDRESSING - SUBNETTING

IP CONFIGURATION

Static DHCP

COMPONENTS OF A NETWORK

Server :Computer that provides shared resources to network users.

Clients :Computer that access shared network resources provided by server.

Media : Way of connecting computers. e.g. Cable, fiber optics, telephone line.

Resources: Files, printers or other items to be used by network users.

NETWORK ARCHITECTURES

Client-server

Peer-to-peer (P2P)

Hybrid of client-server and P2P

CLIENT-SERVER ARCHITECTURE

server: always-on host permanent IP address

clients: communicate with

server may be intermittently

connected may have dynamic IP

addresses do not communicate

directly with each other

client/server

P2P ARCHITECTURE

no always-on server

users directly communicate

peers are intermittently connected and change IP addresses

Highly scalable but difficult to manage

peer-peer

HYBRID OF CLIENT-SERVER AND P2P

Skype voice-over-IP P2P application centralized server: finding address of remote

party client-client connection: direct (not through

server)

Instant messaging chatting between two users is P2P centralized service: client presence detection

user registers its IP address with central server when it comes online

user contacts central server to find IP addresses of buddies

NETWORK TOPOLOGY

Defines the way in which computers, printers, and other devices are connected.

Describes the layout of the wire and devices as well as the paths used by data transmissions.

BUS TOPOLOGY

All the devices on a bus topology are connected by one single cable

At a time only one host can send messages

Passive topology. Hosts on the bus are not responsible for moving data

Failure of any host doesn‟t affect the Network

STAR & TREE TOPOLOGY

Commonly used architecture in Ethernet LAN

Larger networks use the extended star topology also called tree topology

RING TOPOLOGY

FILE TRANSFER OVER NETWORK

FILE TRANSFER OVER NETWORK

CORPORATE INTERNET

IEEE 802 STANDARDS

802.1 Network management and bridging 802.2 Logical link control 802.3 Ethernet and fast Ethernet 802.4 Token bus 802.5 Token ring 802.7 Broadband 802.8 Fiber – optics 802.9 Integrate data and voice 802.10 Security and privacy 802.11 Wireless LAN 802.16 WiMAX (Broadband Wireless Access)

DIFFERENT TYPES OF NETWORKS

Local Area Network (LAN)

Metropolitan Area Network (MAN)

Wide Area Network (WAN)

LOCAL AREA NETWORK (LAN)

A network confined to a single location e.g. one building or one complex

Used for Sharing Hardware e.g. Printers

Software

Data Maximum distance limited by signal strength

LOCAL AREA NETWORK (LAN) …

METROPOLITAN AREA NETWORK (MAN)

A network that covers an entire city

Usually Cable is signal carrier

Maximum range of about 75 kilometers (45 miles) or so, and with high-speed transmission capabilities

T3 = 45 megabits per second (Mbps)

Unlike LANs, MANs generally include provisions for both voice and data transmissions.

WIDE AREA NETWORK (WAN)

A Network spread over wide areas such as across cities, states or countries

High speed data lines used to connect LANs in separate geographical locations

Communication using telephone lines, satellite or Microwave links

WANs can be centralized or distributed

More accurately wide-area internetworks(WAIs)

REQUIREMENTS FOR NETWORK

Server – Win NT/2000/2003, Unix/Linux, Netware

Client – Win XP, Win NT/2000, Linux, DOS NIC – Ethernet Transmission media – twisted pair, coaxial

cables, fiber optics Topology – bus, ring, star, tree Protocol – TCP/IP Interconnection devices – Hub, switch, router,

bridge, gateway

INTERCONNECTION DEVICES

APPLICATIONS

Internet

Email

Downloads

E - Commerce

Group Chatting

Internet Telephony (VoIP)

Video Conferencing

IPTV

Internet Radio

Server based audio & video services

SECURITY

Firewall

Antivirus

TYPES OF MALWARE

Viruses: Code that attaches itself to programs, disks, or memory to propagate itself

Worms: Installs copies of itself on other machines on a network, e.g., by finding user names and passwords

Trojan horses: Pretend to be a utility. Convince users to install on PC

Spyware: Collect personal information Hoax: Use emotion to propagate, e.g., child's last

wish

THANK YOU

Education

Computer networking (nnm)