raj1990 in basic net works

1. Networks Basics
C Viven Rajendra
viven@cse.iitb.ac.in

2. Contents
• What is a network?
• How does it work?
• HUB, Switch, Router.
• Classifying network.
• Proxy, IP, Subnet, DNS.
• WiFi, netmon, simple applications.

3. Computer Network
• A computer network is a
group of interconnected
“network capable
devices”.
• Components : Network
Interface Cards, Hubs,
Switches, Routers and
galvanic cable.

4. How does it work?
• What is communicated?
• When is it communicated?
• How is it communicated?
• Example : Talking, torch light communication.
• We need a protocol : Set of rules governing data
communication.
• TCP/IP is such a protocol.

5. Basic Hardware Components
• Network Interface Card (NIC)
• Hub
• Switch
• Router
• Cable

6. Network Interface Card
• Allows a network
capable device access
to a computer network
such as the internet.
• The MAC address
identifies the vendor
and the serial number
of the NIC which is
unique to the card.

7. Hub
• A network hub or
repeater hub is a device
for connecting multiple
twisted pair or fiber optic
Ethernet devices
together.
• When a packet arrives at
one port, it is copied to
all the ports of the hub
for transmission

8. Switch
• A switch is a device
that performs
switching.
• It forwards and filters
datagrams (chunk of
data communication)
between ports based
on the Mac-Addresses
in the packets.

9. Router
• Forward data packets
between networks
using headers and
forwarding tables to
determine the best path
to forward the packets.
• Processor, OS,
memory.

10. Router

11. Cables
• Category 5 cable, known
as Cat 5 or "Cable and
Telephone", is a twisted
pair cable.(100 Mbps)
• An optical fiber is a glass
or plastic fiber that
carries light along its
length.(40 Gbps)

12. Classifying Networks
• On the basis of scale or extent of reach of network :
LAN, MAN, WAN.
• On the basis of connection method : hardware
technology : Optical fibre, Ethernet, Wireless LAN.
• Functional relationship: Client-Server, Peer-to-peer.
• On the basis of network topology, Physical layout:
Mesh, Star, Bus, Ring, Hybrid

13. Local Area Network (LAN)
• Most current LANs
run on Ethernet and
use the IEEE 802.3
protocol for
communication.
• IITB LAN is a very
good example.

14. Metropolitan Area Network
• Large computer networks usually spanning a city.

15. Wide Area Network (WAN)

16. WAN (contd..)
• Covers a broad area (i.e., any network whose
communications links cross metropolitan,
regional, or national boundaries).
• The largest and most well-known example of
a WAN is :

17. Networking basics
• What is a Proxy?
• What is an IP address?
• What is subnet mask?
• What is Default gateway?
• Domain Name System (DNS)

18. Proxy
• Interface between internal and external
network(Internet)
• Primary advantages:
– Security (from outside)
– Access control ( sites, virus)
– Efficient network utilization due to caching

19. Proxy configuration in browsers
• Institude wide : netmon.iitb.ac.in
• Port 80 for netmon
• LDAP username & password for netmon
• Proxy not required for
– *.iitb.ac.in
– 10.0.0.0/8
• Automatic proxy configuration URL:
– http://www.cc.iitb.ac.in/autoproxy.pac

20. Proxy configuration in browsers

21. Proxy configuration in browsers

22. Proxy configuration in browsers

23. IP address
• An Internet Protocol (IP) address is a numerical
identification that is assigned to devices
participating in a computer network utilizing the
Internet Protocol for communication between its
nodes.
• The format of an IP address is a 32-bit numeric
address written as four numbers separated by
periods. Each number can be zero to 255.
• Mine is 10.2.201.72

24. Subnet mask
• A portion of the network's computers and
network devices that have a common,
designated IP address routing prefix.
• A mask used to determine what subnet an IP
address belongs to.
• An IP address has two components, the
network address and the host address
• Hostel-2 subnet is 255.255.0.0, so allowed
ip-addresses are 10.2.xxx.xxx

25. Default gateway
• A node (a router) on a computer network that
serves as an access point to another network.
• Viewed simply as an entry point and an exit
point in a network.
• A default gateway is used by a host when an
IP packet's destination address belongs to
someplace outside the local subnet.
• Hostel-2 has a computer : 10.2.250.1

26. Default gateway contd..

27. Domain Name System (DNS)
• Associates various information with domain
names;
• It serves as the "phone book" for the Internet
by translating human-readable computer
hostnames, e.g. www.google.com, into IP
addresses, e.g. 208.77.188.166, which
networking equipment needs to deliver
information

28. DNS Example

29. Suggested Material
• Kurose, Ross : Computer Networking: A
Top-Down Approach.
• WikiPedia – Computer Network :
http://en.wikipedia.org/wiki/Computer_netw
ork
• Subnet mask : http://www.tech-
faq.com/subnet-mask.shtml

30. Demo
• SSH
• Putty
• Secure shell
• Pine
• IITB newsgroup

31. Thank You