Hello people today i will be mentioning a few points about the various web related facts in different sections..Yeah u must be murmering among yourself that its all internet what i am going to talk to you about !! Yeah true ,but then i will make you more clear about the various terms we come across in the web technology.Yeah lets now start with basic Internet.
INTERNET
Internet is nothing but a complete large network of all web pages ,nodes clients and servers.
So what is LAN?How does it differ from the internet?
But what makes the difference is the scope it supports.
Intranet is a what comprises of nodes and systems in a small geographical area.
Internet covers the global scope.
Protocols:Set of rules used for communication.
Retrieve pages from the internet:
In order to retrieve pages from d internet there is a complex mechanism that the computer does ,whose complexity is completely hidden from the user.The complexities include the complexities in the hardware ,programs ,protocols and the functions.
Steps:
Now to retrieve a page you start with giving the url in the address bar.
This then reaches the ISP,which is redirected to the DNS.
The URL is then converted to the specific IP address like (123.65.45.21) with the help of the DNS.This conversion is done for the computer to understand the address.
Consider the url http:/google.com.
What does the http stand for??? It stands for Hypertext transfer protocol.It is a set of protocols(rules) which links the hypertext resources all over the internet through the hyperlinks.These rules in a way enable communication with the server.There are different methods used to enable this communication..
- Get -It is used to retrieve a resource from the server,
- Post-It is used to submit the data .
- Put-Its used for insertion in to the server
- Delete-Deletion from the server
- Trace-Echoes back the data from the server.
- Options-Provides us with the available functions from the web server.
- Connect -converts the connection to tcp tunnel
- Patch
Though we don use this functions explicitly it is called implicitly while you access a web page.
Caching a Web Page in Web Server:
There is an option you have to cache a page incase you will use it frequently.The copy of the web page will be stored in the file format in the web server,so the next time access is made easy without delay.
HTTPS
While browsing through certain sites involving transactions you would have noticed that http changes to https.The S stands for Secure.
Https is not a new protocol,it is only a bundled layer of http above the SSL/TLS layer.
The use of the https is to prevent the man in the middle attacks.
In https the data is encrypted during communication.
The data that will be encrypted involves the url,query parameters,cookies and sessions.
Host address and the Port nos are not encrypted cos that is necessary to reach the reciever correctly.
MISCONCEPTION IN HTTPS
----> delay because of the use encryption in HTTPS.
But it is not the fact.Https enables the use of SPDY which reduces the page size.
PORT NUMBER HTTPS
----->This Https uses the port no 443.
----->Each website which is safe gets a valid certificate from either microsoff or verisign and this is verified by the browser to ensure safety in https.
FTP
-->Used for copying files from computer to computer
First it is uploaded from the source client to the server,then it is downloaded from the server to the destination.
-->Uses the Tcp connection.
-->2ports a)command port-port no 21 eg)LIST-lists all the files and folders in the specific folder.
b)data port-port no 20
Works in 2 modes
---->Active mode-server initiates data transfer
---->Passive mode-client initiates data transfer
Passive mode is generally preferred so that the client initiates the data transfer request.
SCP
-->A series of conversation using a single TCP connection
-->Session Control Protocol
Services SCP provides
-->Allows either end of the TCP to create virtual conn and send data .
-->message boundary can be set and incoming msgs can be rejected.
E-TAGS
- It enables web cache validation.
- It improves the cache efficiency and checks the content is unchanged.
- Similar to cookies but is undeletable.
- When a page is stored in the cache ,an etag is stored in the client and one is associated with the particular page.
- If the data changes, the etag with the page changes.Next time while retrieving only if the etags coincides with the one in the client(browser)the copy is retrieved from the cache.Else it is again fetched frm the db server..Thus Etag is more effective.
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