COMPUTER NETWORK ARCHITECTURES Navpreet Singh Computer Centre Indian Institute of Technology Kanpur Kanpur INDIA (Ph : 2597371, Email : navi@iitk.ac.in)

Content Introduction to Computer Networks Overview Of Network Architectures Campus Networks Residential Networks Enterprise Networks Internet How Web Works Network & Internet Security

Introduction to Computer Networks Computer network connects two or more autonomous computers. The computers can be geographically located anywhere.

Introduction to Computer Networks LAN, MAN & WAN 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 Applications of Networks Resource Sharing Hardware (computing resources, disks, printers) Software (application software) Information Sharing Easy accessibility from anywhere (files, databases) Search Capability (WWW) Communication Email, Chat, VoIP Message broadcast Remote computing Distributed processing (GRID Computing)

Network Components Physical Media Interconnecting Devices Computers Introduction to Computer Networks Network Components Physical Media Interconnecting Devices Computers Networking Software Applications

Introduction to Computer Networks 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 HUB, Switches, Routers, Wireless Access Points, Modems etc.

Computers: Clients and Servers Introduction to Computer Networks Computers: Clients and Servers In 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.

Networking Protocol: TCP/IP Introduction to Computer Networks Networking Protocol: TCP/IP

Applications E-mail Searchable Data (Web Sites) E-Commerce News Groups Introduction to Computer Networks Applications E-mail Searchable Data (Web Sites) E-Commerce News Groups Internet Telephony (VoIP) Video Conferencing Chat Groups Instant Messengers Internet Radio

Campus LAN Technology Options Campus Networks Campus LAN Technology Options Ethernet Fast Ethernet Gigabit Ethernet 10 Gig Ethernet WLAN

Campus Network Architecture Server Farm Firewall Router Backbone Switch Internet Distribution Switch Access Switch

Campus Network Architecture Uses Three Tier Switching Architecture (Popularly known as Cisco’s Switching Architecture) Backbone Switch Layer 3/4 Chassis based switch Multiple 100Fx or 1000SX/LX or 10GLX/LH ports for connectivity to Distribution switches Multiple 10/100/1000 ports for connectivity to Servers Distribution Switch Layer 2/3 Managed Fixed configuration switch 1/2 100Fx or 1000Sx/Lx or 10GLX/LH ports for connectivity to the Backbone switch Multiple 10/100 or 10/100/1000 ports for connectivity to the Access switches Access Switch Layer2 Managed/Unmanaged Fixed configuration switch Multiple 10/100 or 10/100/1000 ports for desktop connectivity

Residential Networks: Dial-up MAN Technologies Residential Networks: Dial-up Uses 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.

Residential Networks: Dial-up MAN Technologies Residential Networks: Dial-up RAS

Residential Networks: DSL MAN Technologies Residential Networks: DSL Digital 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)

Residential Broadband: ADSL MAN Technologies Residential Broadband: ADSL

Residential Broadband: Mobile Wireless MAN Technologies Residential Broadband: Mobile Wireless Use CDMA (128 Kbps) or GSM GPRS (384 Kbps) Mobile Wireless

Enterprise WAN Network Enterprise Network Enterprise WAN Network

Enterprise WAN Network Enterprise Network Enterprise WAN Network

Enterprise WAN Network Enterprise Network Enterprise WAN Network Server Farm Corporate Head Office Branch Office Service Provider Network Branch Office All the locations are connected through a Service Provider Network over MPLS Backbone Branch Office

Internet Customers connect to a National ISP ISP network ISP network Backbone ISP Networks Bandwidth-limited links ISP network Customers connect to a National ISP National ISPs connect to International Backbone Networks Customer Networks

Service Provider Networks: Reliance

Service Provider Networks: Reliance Reliance 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 Networks: FLAG

Service Providers National Service Providers: Service Provider Network Service Providers National 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

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

DNS DNS Resolution 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).

DNS Load Balancing 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 Threats Hacking DoS Reconnaissance Malwares Mail SPAM Phishing Botnets

Prevention Techniques INTERNET Security Prevention Techniques Some 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