1. COMPUTER NETWORK ARCHITECTURES
Navpreet Singh
Computer Centre
Indian Institute of Technology Kanpur
Kanpur INDIA
(Ph : ,

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

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

4. 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)

5. 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
, Chat, VoIP
Message broadcast
Remote computing
Distributed processing (GRID Computing)

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

7. 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).

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

9. 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.

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

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

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

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

14. 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

15. 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.

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

17. 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)

18. Residential Broadband: ADSL
MAN Technologies
Residential Broadband: ADSL

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

20. Enterprise WAN Network
Enterprise Network
Enterprise WAN Network

21. Enterprise WAN Network
Enterprise Network
Enterprise WAN Network

22. 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

23. 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

24. Service Provider Networks: Reliance

25. 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.

26. Service Provider Networks: FLAG

27. 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

28. 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

29. 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.

30. 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).

31. 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.

32. INTERNET Security
INTERNET SECURITY

33. INTERNET Security Threats
Hacking
DoS
Reconnaissance
Malwares
Mail SPAM
Phishing
Botnets

34. 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

35. INTERNET Security
WLAN Security