Application Layer Protocols in computer network.pptx

application layer protocols notes ppt

1. Application Layer Protocols By: Sophiya Ghimire

2. Overview Introduction 01 SMTP 02 IMAP 03 POP 04

3. INTRODUCTION Application layer protocols directly support the features ofetwork applications. Application layer protocols directly support the features of network applications. Application layer protocols define the language that network applications speak to fulfill user requests. For example, an application layer protocol defines what message a web browser sends to a remote server to retrieve a web page.

4. SMTP Application layer protocols directly support the features ofetwork applications. The Simple Mail Transfer Protocol (SMTP) is a technical standard for transmitting electronic mail ( email ) over a network. SMTP is used most commonly by email clients, including Gmail, Outlook, Apple Mail and Yahoo Mail. .

5. WORKING MECHANISM Application layer protocols directly support the features ofetwork applications. .

6. WORKING MECHANISM Application layer protocols directly support the features ofetwork applications. . SMTP uses a  client-server  model as follows: An email server uses SMTP to send a message from an email client to another email server . The email server uses SMTP as a relay service to send the email to the receiving email server . The receiving email server uses an email client to download incoming mail via IMAP, for example, and places it in the recipient's inbox .

7. SMTP COMMANDS Application layer protocols directly support the features ofetwork applications. . HELO – Identifies the client to the server, fully qualified domain name, only sent once per session. MAIL – Initiate a message transfer, fully qualified domain of originator RCPT – Follows MAIL, identifies an addressee, typically the fully qualified name of the addressee and for multiple addressees use one RCPT for each address. DATA – send data line by line.

8. SMTP ADVANTAGES Application layer protocols directly support the features ofetwork applications. . If necessary, the users can have a dedicated server It allows for bulk mailing . Low cost and wide coverage area . Offer choices for email tracking . Reliable and prompt email delivery

9. DISADVANTAGES Application layer protocols directly support the features ofetwork applications. . SMTP’s common port can be blocked by several  firewalls . SMTP security is a bigger problem . Its simplicity restricts how useful it can be . Just 7-bit ASCII characters can be used . If a message is longer than a certain length, SMTP servers may reject the entire message.

10. IMAP Application layer protocols directly support the features ofetwork applications. . IMAP stands for Internet Message Access Protocol. IMAP  is an application layer protocol that operates as a contract for receiving emails from the mail server.  It is used as the most commonly used protocol for retrieving emails. 

11. WORKING MECHANISM Application layer protocols directly support the features ofetwork applications. . Email client Gmail establishes a connection with Gmail’s SMTP server . By approving the sender’s and recipient’s email addresses, the SMTP server verifies (authenticates) that the email can be sent . The email is sent to the Outlook SMTP server by Gmail’s SMTP server . The recipient’s email address is authenticated by the Outlook SMTP server. IMAP is used by the Outlook SMTP server to deliver the email to the Outlook email client.

12. ADVANTAGES Application layer protocols directly support the features ofetwork applications. . It offers synchronization across all the maintained sessions by the user . Users have remote access to all the contents . It offers easy migration between the devices as it is synchronized by a centralized server . There is no need to physically allocate any storage to save contents.

13. DISADVANTAGES Application layer protocols directly support the features ofetwork applications. . IMAP is complex to maintain . Emails of the user are only available when there is an internet connection . It is slower to load messages . Some emails don’t support IMAP which makes it difficult to manage

14. POP Application layer protocols directly support the features ofetwork applications. . The POP protocol stands for Post Office Protocol . POP can handle email access only while the emails are sent by SMTP . The version most commonly used today is POP3 (Post Office Protocol 3). It is a standard protocol used by email clients to retrieve emails from a mail server.

15. WORKING MECHANISM Application layer protocols directly support the features ofetwork applications. . POP3 needs to establish a connection between the POP client and the POP server . Once a secure connection is established several commands are exchanged between them . Once a connection is established client requests available email messages. Once the client receives the message, it makes a request to the server for downloading the messages . The server then sends an acknowledgment to the client and closes the connection .

16. ADVANTAGES Application layer protocols directly support the features ofetwork applications. . The message can be read offline also . POP3 requires less storage space . POP3 is easy to use and configure . POP3 is supported by many email applications .

17. DISADVANTAGES Application layer protocols directly support the features ofetwork applications. . POP3 does not provide the feature of real-time synchronization . If an email consists of virus attachments it can affect the system easily . POP3 does not support accessing the same email at the same time on different systems .

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