COMPUTER NETWORK ARCHITECTURES

Navpreet Singh

Computer CentreIndian Institute of Technology Kanpur

Kanpur INDIA

(Ph : 2597371, Email : navi@iitk.ac.in)

Content

Content

Introduction to Computer Networks

Overview Of Network Architectures

Campus Networks

Residential Networks

Enterprise Networks

Internet

How Web Works

Network & Internet Security

Computer Networks

Computer network connects two or more autonomous computers.

The computers can be geographically located anywhere.

Introduction to Computer Networks

LAN, MAN & WAN

Introduction to Computer Networks

Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)

Network in a City is call MAN (Metropolitan Area Network)

Network spread geographically (Country or across Globe) is called WAN (Wide Area Network)

Applications of Networks

Introduction to Computer Networks

Resource SharingHardware (computing resources, disks, printers)Software (application software)

Information SharingEasy accessibility from anywhere (files, databases)Search Capability (WWW)

CommunicationEmail, Chat, VoIPMessage broadcast

Remote computing

Distributed processing (GRID Computing)

Network Components

Introduction to Computer Networks

Physical Media

Interconnecting Devices

Computers

Networking Software

Applications

Networking Media

Networking media can be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means).

Introduction to Computer Networks

Networking Devices

Introduction to Computer Networks

HUB, Switches, Routers, Wireless Access Points, Modems etc.

Computers: Clients and ServersIn a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients.

The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests.

Introduction to Computer Networks

Networking Protocol: TCP/IP

Introduction to Computer Networks

Applications

E-mailSearchable Data (Web Sites)E-CommerceNews GroupsInternet Telephony (VoIP)Video ConferencingChat GroupsInstant Messengers Internet Radio

Introduction to Computer Networks

Campus LAN Technology OptionsEthernet

Fast Ethernet

Gigabit Ethernet

10 Gig Ethernet

WLAN

Campus Networks

Campus Network Architecture

Campus Network

Internet

Server Farm

Backbone Switch

Access Switch

Distribution Switch

RouterFirewall

Campus Network ArchitectureUses Three Tier Switching Architecture (Popularly known as Cisco’s Switching Architecture)Backbone Switch

Layer 3/4 Chassis based switchMultiple 100Fx or 1000SX/LX or 10GLX/LH ports for connectivity to Distribution switchesMultiple 10/100/1000 ports for connectivity to Servers

Distribution SwitchLayer 2/3 Managed Fixed configuration switch1/2 100Fx or 1000Sx/Lx or 10GLX/LH ports for connectivity to the Backbone switchMultiple 10/100 or 10/100/1000 ports for connectivity to the Access switches

Access SwitchLayer2 Managed/Unmanaged Fixed configuration switchMultiple 10/100 or 10/100/1000 ports for desktop connectivity

Campus Network

Residential Networks: Dial-upUses POTS (Plain Old Telephone System)

Provides a low cost need based access.

Bandwidth 33.6 /56 Kbps.

On the Customer End: Modem is connected to a Telephone Line

On the Service Provider End: Remote Access Server (RAS) is connected to Telephone Lines (33.6 Kbps connectivity) or E1/R2 Line (56 Kbps connectivity)

RAS provide dialin connectivity, authentication and metering.

Achievable bandwidth depends on the line quality.

MAN Technologies

Residential Networks: Dial-up

MAN Technologies

RAS

Residential Networks: DSLDigital Subscriber Line (DSL) uses the Ordinary Telephone line and is an always-on technology. This means there is no need to dial up each time to connect to the Internet.

Because DSL is highly dependent upon noise levels, a subscriber cannot be any more than 5.5 kilometers (2-3 miles) from the DSL Exchange

Service can be symmetric, in which downstream and upstream speeds are identical, or asymmetric in which downstream speed is faster than upstream speed.

DSL comes in several varieties:Asymmetric DSL (ADSL)High Data Rate DSL (HDSL) Symmetric DSL (SDSL) Very High Data Rate DSL (VDSL)

MAN Technologies

Residential Broadband: ADSL

MAN Technologies

Residential Broadband: Mobile Wireless

MAN Technologies

Use CDMA (128 Kbps) or GSM GPRS (384 Kbps) Mobile Wireless

Enterprise WAN Network

Enterprise Network

Enterprise WAN Network

Enterprise Network

Enterprise WAN Network

Enterprise Network

Server Farm

Service Provider Network

All the locations are connected through a Service Provider Networkover MPLS Backbone

Branch Office

Branch Office

Branch Office

Corporate Head Office

Internet

Internet

• Customers connect to a National ISP

• National ISPs connect to International Backbone Networks

BackboneISP Networks

ISP networ

k

ISP networ

k

ISPnetwork

Customer Networks

Bandwidth-limitedlinks

Service Provider Networks: Reliance

Service Provider Network

Service Provider Networks: RelianceReliance Data Centers, are connected to 132 countries across 4 continents spanning US, UK, Mid-east and Asia-Pac through Flag Telecom backbone (Reliance Infocomm 's group company) and other undersea cable systems like Se-Me-Wea-3 and i2i and are having public / private peering relationship with large Tier 1 ISPs and content providers at more than 15 Internet Exchange points across the globe. There also exists peering relationship with other popular domestic ISPs on STM-1 bandwidth levels.

The data centers further are connected to Reliance's country wide optic fiber based IP network with terabytes of capacity having points of presence at more than 1100 cities. Customers' can access the Internet by connecting to any of these 1100 PoPs using multiple means like local dedicated leased lines, PSTN -ISDN dialup links OR simply by using Reliance's 3G CDMA mobile services.

The Reliance Data Centers at various locations are also interconnected through redundant fiber ring with bandwidth capacity of STM-4 for data replication purposes for providing Disaster Recovery services.

Service Provider Network

Service Provider Networks: FLAG

Service Provider Network

Service ProvidersNational Service Providers:

VSNL

Reliance

BSNL

Bharti

Satyam

International Service Providers (connecting India to the World)

Flag

SingTel

NIXI (STPI Delhi, Mumbai, Kolkata & Chennai) provides peering connectivity between Indian ISPs

Service Provider Network

How Web Works?Let's say you want to visit the google website.

First you enter the address or URL of the website in your web browser.

Then your browser requests the DNS Server to get the IP address of the web server

WWW

How Web Works?Then your machine sends an HTTP request to the web server that hosts the google site.

The server sends the data over the Internet to your computer.

Your web browser interprets the data, displaying it on your computer screen.

WWW

DNS Resolution

DNS

DNS is a network service that enables clients to resolve names to IP address.

A DNS server maintains the name to IP address mapping of the domain for which it is the name server

The DNS server for a domain is registered with the domain registrar and the entry is maintained by the root-servers.

Whenever a DNS for a server is queried, the root servers are contacted.

The root servers replies with the IP address of the DNS server of the domain (for higher level domains) or forwards the request to the country root servers (four country specific domains).

Load Balancing

DNS

DNS supports Load Balancing: The same name resolves to multiple IP Addresses (IP addresses of different Mirrored servers).

Companies like akamai provide "Enhanced DNS" services:

Different DNS results based on source IP.

Web browser could automatically be directed to the closest web server thus reducing the download time

Companies like akamai maintain mirror sites of many organizations on their server and direct request for these sites to the nearest server.

INTERNET Security

INTERNET SECURITY

INTERNET Security ThreatsHacking

DoS

Reconnaissance

Malwares

Mail SPAM

Phishing

Botnets

INTERNET Security

Prevention TechniquesSome of the prevention tools include:

Network Firewall

Host Firewall

IDS/IPS

Mail Antispam and Antivirus Appliances

UTM Appliances

Application and OS Hardening

INTERNET Security

WLAN Security

INTERNET Security