More protocols: DHCP and NAT
Unit 4: Networks
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Introduction
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Now we have almost built the whole TCP/IP model we have a set of Protocols in place that
can reliably transfer data between devices. We can now use this TCP/IP connectivity to
make the setting up of networks easier, automate some of the internal processes and
make using networks easier for the end user.
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Where did your device’s IP address come from?
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Where did your device’s IP address come from?
On a local LAN your device’s IP address will be one of those from the private IP address range:
192.168.X.X. Have you ever had to set your device’s IP address? The answer is “no”, so something
must be happening automatically.
Whenever a device connects to any network, its first action is to try and discover where it is and what IP address it should use. It
does not know what IP address to send such a request to, so it sends out a broadcast IP packet to a special broadcast IP
address: 255.255.255.255. In binary that’s 11111111.11111111.11111111.11111111, so this address is also called the all-ones
address. At the Ethernet layer, device also doesn’t know which device to send the frame to, so again it sends it to the special
Ethernet Broadcast address: FF:FF:FF:FF:FF:FF.
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Your Turn! Questions
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2)
3)
Port numbers ensure that data is delivered to the correct application, but can you think of
another use of port numbers that relates to security?
If you are watching a video on a streaming site, the video may be ‘buffering’ for several seconds
before it starts playing. What is going on there?
In a congested network, packets may be delayed and there may not be enough memory to
store them. What happens in such circumstances?
Post your answers to the Discussion Board!
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