The document discusses various application layer protocols including DNS, SMTP, FTP, HTTP, and web applications. It provides the following key points: - Application layer protocols are divided into those used directly by users like email and those that support user protocols like DNS. - DNS translates domain names to IP addresses to direct web traffic. SMTP is used for email transmission over the internet while FTP transfers files. - HTTP transfers web pages over the internet in a similar way to FTP but delivers messages immediately unlike SMTP's store-and-forward system. - The world wide web is a collection of globally linked web pages accessed through URLs over HTTP using the client-server model of a web server producing and delivering information to

1. APPLICATION LAYER
By B.SAKTHI MCA., M.Phil.,
Assistant professor
V.V.Vanniaperumal College forWomen
Virudhunagar

2. APPLICATION LAYER
Application layer protocols divided into two categories.
• Protocols which are used by users eg. E-mail.
• Protocols which help and support protocols used by users
eg: DNS

3. Domain Name System (DNS)
DNS works on client server model
• It is an internet service that translate domain name into IP address.
• Eg. www.gmail.com
198.20.8.1
11000110 10100 1000 001

4. SMTP (Simple MailTransfer Protocols)
 It is an interne for e-mail transmission.
 SMTP connections are secured with SSL (Secured Socket
Layer)
 In SMTP, the message are stored and then forwarded to
the destination.
 SMTP was a port number 25 of TCP

5. FTP (FileTransfer Protocols)
 It is used to exchange file on the internet
 To enable the data transfer FTP uses TCP/IP
 FTP is most connecting used to upload and download from the
internet.
 FTP can be invoked from the command prompt or some graphical
user interface.
 FTP also allow to update (delete, rename, move and copy) files at a
server.
 It uses a reserved port no 21

6. HTTP ( HypertextTransfer Protocol )
 Hyper text transfer protocol (HTTP) is use to access the data www ( world
wide web)
 The functions of HTTP are the combination of FTP and SMTP.
 HTTP is similar to FTP, because it uses only oneTCP connection data is
transferred between client and server.
 In SMTP, the message are stored and then forwarded to the destination
but HTTP messages are delivered immediately.
 HTTP used the services ofTCP on well known port no 80.

7. WORLDWIDEWEB (WWW )
 It is a huge collection of pages of information linked to each other
around one globe.
 Every page is a combination of text, picture, audio, video, animation
and hyperlink.
 Berness lee is the father of WWW.

8. Web page
 It is a collection of normal text picture, video clip, audio clip,
hyperlink.
 It can be designed with html, xml, java script etc.,
 HTML – design structure
 JavaScript – Validate the field
 XML – is advance version of html.

9. Website
 It is a collection of interlink webpages (hyperlink -> navigate to
another page).
 Website is accessed through URL (address) eg. www.gmail.com
 URL is a global address of web document on www.
 URL are unique in nature may don’t have copy.
 There are 2 ports in URL.
 protocol eg. httpwww.google.com
 Resourse name

10.  Website is categorized according to there function
 personal website
Commercial website
 government website
 There are 2 types of website
I. Static – information site
II. Dynamic – interactive site.

11. WebApplication (Web App)
 We can run web app web the browser through URL.
 There are 2 types of wep app.
I. Service oriented
II. Presentation oriented

12. Service oriented:
 It is used to implement web services.
 It is coded using CGI, JSP, ASP.
Presentation oriented:
 It provides client side services.
 They are coded using HTML, XML, Java script etc.

13. WebArchitecture
WWW follow 2 tier architecture
• It is a combination of webserver and web client.
• Webserver produce and deliver the information.
• Web client retrieve and display the information.