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Session Objectives#18

MUST describe common file standards associated with the internet such as JPG,GIF,PDF,MP3,MPEG.

SHOULD Describe the differences between lossy and lossless compression and explain the importance of compressing files that are transmitted via the internet

COULD explain the need for IP addressing of resources on the internet and how this can be facilitated by the role of DNS services

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Key WordsKey Words

DNS

LossyLossless

IP Address MAC Address

Compression

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IP & MAC Addresses

What is this?? 72.163.4.161 IP Address of Cisco Headquarters, California, USA

To the computer this address is made 32 bits or 4 bytes which it converts each into binary. Going from left to right what is the binary equivalent?

01001000, 10100011, 00000100, 10100001Or 01001000101000110000010010100001

You can see why humans prefer to use denary!

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IP & MAC Addresses

IP Addresses are unique to an individual computers location over the internet. The addresses are acquired by the Internet Service Provider (ISP) or a DHCP server or Dynamic Host Control Protocol for an internal network.

A Smartphone is the same, it is issued with an IP address from DHCP server at the mobile carrier. It may change during the day but will unique for the time it has been assigned.

TASK: Check to see your current IP address.

MAC Addresses – These are still unique identifiers but are hard coded into each device. They are much bigger – 48 bits – and uniquely identify each device in the world.

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IP Addresses MAC Addresses

IP & MAC Addresses

IP Addresses MAC Addresses

32 bits 48 bits

4 sets of decimals 6 pairs of hexadecimals

Can be changed manually or assigned automatically by a DHCP server

Permanently ‘hard coded’ into each device in the world.

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File Compression

TASK 1: Use the following online tool and compress some images:http://compressnow.com/# Use Chrome!

Now answer these questions in your notes:What is compression? What affect does it have and why use it?Research and create a comparison table of lossy and lossless compression algorithms.

Lossy LosslessLossy Lossless

Data is lost when compressed Data is retrieved when decompressed

Some data lost but hardly noticeable Restored completely to original

Greatest file reduction made Not as much data can be reduced

Most common form for Internet use as download speed is paramount

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File standards of the Internet

TASK:Use the 2UP view in Fireworks and experiment optimising different file types. Then complete the following table explaining the circumstances which each file type would be used.

EXT: Extend the table to include other files associated with the Internet.

File Type Description/ExplanationsGIF JPGPDFMPEGZIPMP3