Notes on the Internet Internet services Communications hardware URL DNS Protocol TCP/IP, TCP/IP address, classes, sub netting Packet switching Internet security Internet regulatory boards/organisations Security and privacy RSA/PGP Internet use and the law Web resource information
HTML – Tags you need to know,,,,,,,,,,,,,. Visit W3Schools http://www.w3schools.com/html/
Gateway Routers A router which provides access from one network to another If a packet is sent to a destination which is not on the network, it is sent to the gateway address first
Data Protection Act Forms where people enter details Saved on their server Applies to all blogs
Computer Misuse Act Creating and Sending viruses Spyware installation Hacking a network
Need for International Policing of the Internet. Why it wont happen - Each country has separate legal systems - Dont want to lose control. - UN style org. Why would it be good - Prevent more crime - Censorship would be universal.
Academic, Commercial and Personal web pages http://www.cristianoronaldo.com/ http://www.snp.org/people/alex-salmond http://www.lilyallenmusic.com/ http://www.amazon.com/ http://www.debenhams.com/ https://retail.santander.co.uk https://www.edx.org/ https://www.edx.org/ http://www.st-andrews.ac.uk/
Browsers HTML interpretation – X Ray goggles client side scripting - http://www.w3schools.com/js/default.asp cookie functions - http://www.w3schools.com/js/js_cookies.asp built in encryption functions - http://www.w3schools.com/php/func_string_crypt.asp
The rules of cascading stylesheets state that: embedded styles within the text over-rule all others document level styles, defined in the document, over-rule external Stylesheets external stylesheets only apply if they are not over-ruled by the other 2 methods
Encryption – Putting the data into code A = B = C =
Encryption –Asymmetric The person who will receive the data decides on a private key The RSA algorithm generates a public key which will be used to encrypt the message it is mathematically (almost) impossible to calculate the private key from the public key.
PGP – X send Y a message 1.PGP first compresses the message - harder to decode the message 2.PGP then creates a session key, which is a one-time-only secret key 3.session key itself is encrypted using Ys public key. 4.AXcrypt
PGP – Y receives the message 1. Ys copy of PGP uses his or her private key to decrypt the temporary session key. 2. PGP then uses the session key to decrypt the encrypted Message. This is the most secure and quickest means of encryption
The firewall software can be set up to: reject packets from selected IP addresses (for example, blocking inappropriate sites) allow only packets from selected sites reject or allow packets from particular domain names only allow packets to and from certain ports (a useful defence against many viruses) allow or reject packets using particular protocols (for example, blocking all FTP requests) "sniff" packets, and reject any which contain certain words
cascading style sheets A cascading stylesheet (CSS) is a separate file which defines colours, fonts and sizes to be used on web pages. A reference to this file is included within every web page in a website. This ensures that each page is consistent in format.
client side scripting (including form validation and alerts). Server-side scripting is a web server technology in which a users request is fulfilled by running a script directly on the web server to generate dynamic HTML pages
page structure and layout The layout and structure of a page should make it easy for a reader to find information.
uniformity of presentation style sheets server-side scripting – client side not possible using a non-compatible browser, pages look the same to all dynamic pages -content is stored in a database of files, bbc etc.
download efficiency Ensure all graphics are re-sized and at screen resolution (normally 72dpi), and saved as compressed JPEG or GIF files.
Packet switching Why packet switching? Need for IP 10.10.8.10 18.104.22.168 Packet 2 Packet 3 Packet 4 Packet 1:5 Packet 5
TCP/IP classification 32-bit IP address Network ID Host ID 32 BITs Network IDHost ID
Sub Netting Network masks used to split network into smaller networks Used to determine what subnet an IP address belongs to. Eg first four bits of host address removed to identify subnet Network address plus bits reserved for identifying subnetwork
Internet security Viruses Un-authorised access (hacking) Denial of service attacks Information theft
Internet regulatory boards IETF IANA W3C NOMINET
Security and privacy Packet filtering Firewall Proxy server Packet filter router Or Firewall Or Proxy server Internet Host ID22.214.171.124
Security Encryption Key distribution problem RSA PGP Browser encryption Secure sockets
Law Data Protection Act 1984, 1989, 2000, 2004 Copyright, Design & Patents Act 1988 Computer Misuse Act 1990
Policing the Internet Need for international agreement Problems reaching international agreements
HTML Client side Server side Client side Server side
HTML structure Start of document marker /End of document marker Heading /End of Heading Body /End of body This area is not displayed The content, which is displayed in the browser
HTML Body Head Html Align Table H1-h6 Tr td th Img src Span Div Font family A href P br
HTML tags definitions Browser recognises and interprets HTML script instructions Ignore text