Static Websites vs Dynamic Websites
Static Websites
The user makes a page request the sever runs a script and returns the requested page to the user as fixed HTML.
Dynamic Websites
Processing occurs on the clients machine
The user makes a page request the sever runs a script and returns the requested page to the user as HTML and JavaScript.
The JavaScript then may make additional requests to the server and updates the web page accordingly.
Client Server Model
Client Server Model
The client requests data from a server that then then responds
Peer to Peer
Devices are both requesting an serving data concurrently
Data Centers
Servers
Server’s can have many different uses
- Web
- Application
- Database
- Media
- Authentication
Support Hardware
Data centers contain hardware to support and maintain the servers:
- Server racks
- Backup servers
- Air conditioning
- Backup generators
- UPS (uninterruptible power supply (Batteries))
Data Duplication
In data centers data is duplicated so that if a server breaks then another server can take over and continue to provide the data
The Internet
Communication
The majority of data traves through wires and cables.
Undersea cables are the primary way for continental communication
Satellites and other communication methods may be used but this is generally rare.
Data Locality
Generally the shortest path is used to obtain data if data is in the UK requests and information typically will not leave the country. If the data is in America then a request will be mad to America. The shortest path is not guaranteed as the internet is a web many different paths exist.
Packets
Packet’s are addressed and then routed to the correct location. Packets are transmitted across many computers on the way to the destination
Routing
Routing involves checking if the destination is known to a computer and then directing the traffic in the correct location, if the location is not known then another computer higher up the chain is asked.
Mobile Web applications
Phone and tablets have many constraints
- Lacks hover
- Lack processing power
- Lack screen sizes
- Variety of screen sizes
However rather than having a dedicated web app browser apps can be made to run in small browsers on the phone and websites can be converted over.