Computer network

1. Computer Network
Subrata Paul
Roll : 13015411
DEPT. of CSE
University of Rajshahi

2. x

3. Context:
 What is switch ?
 Working of switch.
 Characteristics of switch.
 Some manufacturer of networking switch
 What is Hub.
 Characteristics of Hub.
 Working of Hub.
 Comparison of switch and hub

4. What is switch ?
A network switch is a computer networking device that is
used to connect multiple computer together within on local
area network(LAN). In other words, it is capable to
determine specific source and destination.
Technically, network switch operate at layer two (Data link
layer) of the OSI model. The network switch commonly refers
to routes data at the data link layer of the OSI model.

5. Working of Switch
Switch is an interconnecting device with 16 or 24 ports
in common. All other devices are connected to these ports .
Whenever any machine sends packet to any other machine,
source machine send packet to switch, switch then forwards
it to destination machine. Each packet which comes to
switch contains source and destination physical address in
it, on basis of which switch forwards packet to other
machine. Switch always sent packet based on destination
MAC address. Its process is as follows: (process also
known as Switching)

6. Working of Switch (continue..)
 When switch receives a packet from any device, it checks for its
destination MAC address.
 Then switch compares destination MAC address with its MAC
Address Table for corresponding MAC address.
o If MAC Address is found, packet is sent out to port against which
MAC Address was matched.
 If entry is not found, Unknown unicasts (when the switch doesn't have a
port mapping for a destination mac address in the frame) are treated like
broadcasts by Layer Two devices, and are flooded out of all ports except
the port on which the frame originated.

7. Working of Switch (continue..)
Now question comes, how does switch knows on which port
destination machine is connected?
For this switch uses one table in its cache memory called MAC
Address table or Forwarding Table in which switch stores that at
which port which machine is connected by storing its physical
address (MAC Address). So table contains two columns (Physical
Address and Port Number) and rows equal to number of ports in
switch. When switch is turned ON, by default there is no entry in
MAC address table, as communication starts, based on devices
involved entries are created in table

8. Characteristics of switch
 Uses MAC address for data transfer.
 Filter data before forwarding it to its destination of on the
network.
 Connect LAN segments.
 Multiple collision domain but single broadcast domain.
 Layer 2 (data link) device.
 Data transfer to specific port.
 Transmission mode are full duplex.
 No collision occur in in full duplex.
 Data transmission form are frame.

9. Different type of switch

10. Some manufacturer name of switch
 D-Link
 Billion Electronic
 ECI Telecom
 Cisco Systems
 Juniper network
 Oracle corporation

11. What is hub ?
Hub is the most basic networking device that
connects multiple computers or other network
devices together. a network hub has no routing
tables or intelligence on where to send information
and broadcasts all network data across each
connection.

12. Characteristics of Hub
 Hub propagate signals through the network.
 It cannot determine the best path.
 It cannot filter network traffic.
 Layer 1(physical layer) device.
 Centralize device.
 Connect multiple Ethernet device together.

13. Working of Hub
When a packet arrive at one port from a source it is copied to
the other ports so that all segments of LAN can see all packet
and hub forward the segments to all connected devices then
accept this segment only expected destination other device
discard this segment.

14. Working of Hub(continue…)

15. Working of Hub(continue…)
This simulation illustrates the basic operation of a hub.
Computer 1 sends a ping message to Computer 3. when the ping
reaches the hub, it doesn’t see the actual data
In the message. It only sees bit signals, cleans them up and
Sends them out all connected ports.
When Computer 2 and 4 receive the bits signals they reassemble
them into frame, check the destination address
And discard the frame because it is not addressed to them.
Computer 3 receives the frame successfully and sends a
Reply.
.

16. Working of Hub(continue…)
Once the reply sends the hub, the hub again forwards the bit
Signals out all connected ports, Computer 2 & 4 discard the
Fram.e Computer 1 successfully receive the ping reply

17. Comparison of switch and
hub
Suppose, we have four computer, four computer are
connected to a hub, now two computer of them
communicate with each other, hub simply pass the
message through all network traffic to each of four
Computer, where a computer receive this message.
On the other hand, switches are capable of determining
the destination of each individual traffic element and
selectively forwarding data to the one computer that
actually need it.