Internet Unit

Structure of a URL


http://www.Click&Get.co.uk/images/CG212.jpg 


protocol - http:// 
domain name - www.Click&Get.co.uk 
path - /images 
port - 21
file identifier - /CG212.jpg 


W3C 


W3C (1 mark) 
developments / standards (1 mark) 
on the WWW (1 mark) 
deals with HTML (1 mark) 


ICANN


ICANN (1 mark) 
• responsible for distribution of IP addresses and domain names (1 mark) 
OR 
• as they will need more IP addresses for the greater number of users


TCP/IP


1. A packet is a block of data 
2. with a header added 
3. with the source address 
4. packet number/length/protocol 
5. and destination addresses attached 


6. Routers in the Internet look at the destination address 
7. and use lookup tables to decide where to send the packet next 
8. which may be the destination or another router 
9. each packet is routed (may be different route) 
10. if does not arrive, will be re-transmitted 
11. packets are reassembled at destination using packet number 


Classes of networks    Class A        Class B        Class C




Networks                        127               16,000           2m

Hosts                              16m               65,000           254


Benefits of subnet masking


more flexibility in terms of number of hosts and networks


useful for small companies who don’t require 254 hosts 


Subnet Masking


128  64   32  16    8    4    2    1
 n        n     n       n     h      h    h      h


Write the subnet mask out in binary


Count the hosts – in this case 4


Use the formula 2h - 2 to find the number of hosts


PHP


• The site has content which changes frequently (is dynamic) 
• Such as Number in Stock and date 
• Content like this ideally held in a database 
• php interfaces well with database such as SQL 


SSL


SSL uses IP addresses to make a secure connection 
SSL uses encryption (1 mark) with public (1 mark) and private keys (1 mark).




Client Side Scripting


• Should be faster than server side scripting 


• Validation/Error trapping is improved 


• Individual fields can be checked rather than waiting for form to be submitted. 


• Less load on server/doesn’t affect server performance 


Benefits of using domain names over IP addresses


domain names are words/meaningful (1 mark) not just numbers (1 mark) OR


domain names are used by people (1 mark) not by computers (1 mark)) OR 


easier to remember (1 mark) than strings of numbers (1 mark) 



HTML  codes



Inserting an image


<img src="Zologo.jpg" alt="Zologo" height="70" width =”120”> 


Linking to an email address


<a href = mailto:mranderson@BuchanHighSchool.sch.uk >Mr Anderson</a> 


Benefits/Drawbacks of Web Design software


Advantages
• Don’t have to learn HTML code
• WYSIWYG
• Speed of development
• Easier to use (for a beginner)
• Special effects are easily produced
• Easy to change layout
• Provides online help
• Any other appropriate answer


Disadvantages
• Have to learn how to use the software
• Some are quite complicated touse
• Creates large file size
• Produces bloated or extraneous code
• Slower to load
• Expensive to buy
• Any other appropriate answer


How to add new pages to a website


Upload her files (1 mark)
to the correct folder (1 mark)
Create a link to the page (1 mark)
on her hosting server (1 mark) 


Web Site Design Issues


Page structure/layout (1 mark) ensuring web pages are consistent by catering for
• different screen display sizes
• resolutions
• colour depth
• browser types
• user preferences
• available fonts
• users changing window size
or
Uniformity of presentation (1 mark) ensuring each web page is laid out in a similar manner (1 mark) or to give the user a familiar environment
(1 mark)
Or Download efficiency (1 mark) ensuring that the web pages will not take too long to download (1 mark) or striking a balance between the number of images and the time needed to transmit the images (1 mark)
or
Browser compatibility issues (1 mark) different browsers interpret HTML scripts differently resulting in different displays in different browsers (1 mark) or some web pages will be displayed differently depending on the browser (1 mark)


PGP


This method involves the use of keys, a public key and a private key (1 mark). A public key is freely available to everyone on the Internet and is used to encrypt the message (1 mark). A private key is secure and is used to decipher the message.


CSS


A cascading style sheet is a set of rules for a number of text formatting
controls (1 mark) that can be linked to a number of web pages (1 mark).
OR
A language (1 mark) used to describe how an HTML document should be
formatted (1 mark).


Cookies


A short piece or file of text/code (1 mark) stored by a website on a client