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Web Components (Assessment 1, Topic 2)
Transcript of Web Components (Assessment 1, Topic 2)
Topic 1: Web architecture
Topic 2: Web components
Topic 3: Web functionality
Topic 2: Web Components:
Mail and proxy servers
TCP/IP - transport and addressing
Application layer – HTTP, HTTPS, SM
Hardware: Web, Mail and Proxy Servers
Web Architecture and Components
Protocols: Application Layer
The router's role in a network is to deliver a message from one device to another
This message is called a 'packet'
Routers decide the best route for the packet
A packet may travel through many routers on its journey from one computer to another
Most of these routers will belong to ISPs
One ISP router will start the packet's journey and another ISP router will finish it and deliver to the destination - with many in between
The first layered protocol model for internetwork communications was created in the early 1970s and is referred to as the Internet model.
It defines four categories of functions that must occur for communications to be successful.
The Internet model is commonly referred to as the TCP/IP model.
layer contains protocols that allow network communication to happen between different devices. E.g.
e-mail protocols (SMTP and POP)
web protocols (HTTP, HTTPS)
File Transfer protocol (FTP)
Layer - deals with reliable delivery of the data.
The data is chopped into smaller pieces (that will become packets)
Each is given a sequence number so that it can be pieced together again at the other end.
TCP protocols contact the receiving device before sending the data - to establish the connection (3-way handshake)
TCP also organises for acknowledgements to be sent to confirm that each packet has been received.
Layer - this layer deals with addressing each packet (IP address) and then ensuring the data gets to the correct destination using a series of routers. Each router reads the IP address and routes it to the next on the journey.
layer. This layer deals with hardware and software that allows the data to access and travel on the media (e.g. fibre optic cables, copper cables, wireless, satellite). It contains protocols that determine how the data accesses the media (e.g. Ethernet, Token Ring).
4 Layers described
Common Application layer protocols:
HTTP - Hypertext Transfer Protocol - protocols for using the World Wide Web
SMTP and POP - e-mail protocols
FTP - File Transfer Protocol - used to upload files to a server
IMAP - Instant Message Access Protocol
There are many others
These protocols are rules that determine how different types of communication take place
They will work no matter what hardware you are using
The Hypertext Transfer Protocol (HTTP), one of the protocols in the TCP/IP suite, is used to publish and retrieve HTML pages from a web server. You can purchase space on a web server from external companies to store your website. These companies often also provide website management facilities too - maintaining uptime, providing traffic monitoring and technical support
When e-mail was first developed both the sender and receiver had to be online at the same time. Now your e-mails will be stored on a server waiting for you to access them (store and forward). This can be a server owned by your ISP, or may be a specialist web based e-mail server (e.g. Hotmail). Big companies will have their own e-mail servers
A proxy server is an intermediary computer that is between the user's computer and the Internet. It can act as a firewall and content filter. It can also improve performance by caching (storing) web pages accessed by hosts on the network for a certain amount of time. Whenever any host requests the same web page, the proxy server uses the cached information instead of retrieving it from the content provider. This leads to quicker access of the web pages.
Web based e-mail
You can use free, web based e-mail services such as Yahoo, Hotmail, GMail, etc.
These allow you to pick up your e-mail from anywhere.
Client based e-mail
Alternatively you can use a client based e-mail such as Microsoft Outlook or Mozilla Thunderbird (free download) - the software is stored on your computer and can only be accessed on your computer (although web-based versions of Outlook are now available)
You need to specify a server for your e-mails to be stored on (your ISP will provide this service).
You also can purchase e-mail software, e.g. FastMail
- provides multiple e-mail addresses and backup
A browser is software that you need in order to view web pages
Multimedia content can be displayed and hyperlinks are provided to navigate through content
There are many different Browsers - Internet Explorer (provided with Windows), Mozilla Firefox, Google Chrome
Safari and Opera are Browsers for the Apple Platform
There are lots of different servers on the internet that provide different services. These servers are often owned by big companies or Internet Service Providers
Warriors of the Net
What is a Protocol
A protocol is an agreed way that different systems can talk to each other - like a 'rule'
The internet uses hundreds of different protocols (rules) to define a method of exchanging data over a computer network such as local area network, Internet, Intranet, etc.
Each protocol has its own method of how data is formatted when sent and what to do with it once received, how that data is compressed or how to check for errors in data.
Compare to different protocols (or rules) for driving on our roads - there are different rules according to the type of road (e.g. traffic lights, zebra crossings, junctions, speed limits, etc.)