A small presentation on the basics of Switching and Forwarding in Computer Networks.

1. Switching & Forwarding
By Md. Naseem Ashraf
BE/5504/09
A Presentation for Computer Networks
Birla Institute of Technology, Mesra, Extension Center - Patna

2. Where else have we seen this problem
before the advent of computer
networks?
• Limit on the Number of Hosts
• Limit on the size of Geographic Area a
network serves
What was the problem with Directly
Connected Networks?
Answer: Telephone Networks

3. Solution from the Telecommunication
Industries
• Use of a call exchange to switch your call
to the desired destination (Forwarding).
• Switches create an impression that
you’re connected to the receiver of the
call.

4. Caller
• Set on another
network of
cables
elsewhere
Telephone
Exchange
• Is a Switch
with all
networks
connected
Receiver
• Set on
another
network of
cables

5. Switches in Computer Networks
• Computer Networks use Packet Switches.
• No direct connection is required between
hosts.
• A Multi-input, multi-output device which
transfers packets from an input to outputs.
• They maybe servers, computers, satellites etc.
But, Still, What are Switches?

6. Summarizing Forwarding Features of
Switches
• Switches do have a fixed number of inputs &
outputs limiting the number of hosts. But,
why care? Just connect them, switches,
together.
• They can span larger geographic area.

7. Key problems to look at when using
Switches
• They have Finite bandwidth of its outputs.
• Contention:
Arrival Rate of Packets > Delivery Rate of Packets
• Buffering:
The use of storage buffers by switches to keep a certain
amount of input stored to balance contention.
• Congestion:
The loss of data packets when the buffer limit is
exceeded and contention is not controlled; The incoming
packets are discarded too frequently.

8. That’s all for Today, Folks!!
END GAME