Dcn ppt 150050705008

http & smtp
SUBJECT: DATA COMMUNICATION NETWORK (2720507)
Submitted by: guided by:
Talsaniya bhargavi a(150050705007) PROF.TWINKLE DOSHI
THAKOR JAYDEEP (150050705008) HOD EC Dept
Communication system eng. Bits,varnama,vadodara
Bits,varnama,Vadodara

OUTLINE
 What is a protocol ?
 HTTP:
 OVERVIEW
HTTP CONVERSATION
EXAMPLE
 SMTP
OVERVIEW
COMMAND AND RESPONSES
MAIL TRANSFER PHASE
2

What is a protocol?
 In diplomatic circles, a protocol is the set of rules
governing a conversation between people
 We have seen that the client and server carry on a
machine-to-machine conversation
 A network protocol is the set of rules governing a
conversation between a client and a server
 There are many protocols, HTTP ,SMTP are from it

Many application layer protocols are used on
the Internet, From Which
Protocol Application
HTTP: Hypertext Transfer Retrieve and view Web pages
SMTP: Simple Mail Transport Send email

 I would like to open a
connection
 GET <file location>
 Display response
 Close connection
 OK
 Send page or error message
 OK
Client Server
HTTP is the set of rules governing the format and content of the
conversation between a Web client and server
An HTTP conversation

HTTP :
an application layer protocol
 The Web client and the Web server are application programs
 Application layer programs do useful work like retrieving Web pages, sending
and receiving email or transferring files
 Lower layers take care of the communication details
 The client and server send messages and data without knowing anything
about the communication network

The application layer is boss – the top layer
Layer Function
Application Do useful work like Web browsing, email, and file
transfer
Lower layers Handle communication between the client and server
 Your boss says: Send this package to Miami -- I don't care if you use Federal
Express, UPS, or any other means. Also, let me know when it arrives or if it cannot
be delivered for some reason.
 The application program says: Send this request to the server -- I don't care how
you do it or whether it goes over phone lines, radio, or anything else about the
details. Just send the message, and let me know when it arrives or if it cannot be
delivered for some reason.
There are five TCP/IP layers, the application layer and four lower layers.

An HTTP example
The message requesting a Web page must begin with the work “GET”
and be followed by a space and the location of a file on the server,
like this:
GET /fac/lpress/shortbio.htm
The protocol spells out the exact message format, so any Web
client can retrieve pages from any Web server.

The TCP/IP protocol layers
Application
Transport
Internet
Data link
Physical
Get useful work done – retrieve Web pages, copy files,
send and receive email, etc.
Make client-server connections and optionally control
transmission speed, check for errors, etc.
Route packets between networks
Route data packets within the local area network
Specify what medium connects two nodes, how binary
ones and zeros are differentiated, etc,
The application program is king – it gets work done using the lower level layers
for communication between the client and server.

SMTP: Simple Mail Transfer Protocol
• Simple Mail Transfer Protocol (SMTP) is a standard set of rules and
procedures by which messages can be transferred over the Internet. is
used by Mail Servers to send messages back and forth to other Mail
Servers or Email Clients.
• List of SMTP commands:
HELO
RCPT TO
MAIL FROM
DATA
QUIT

MESSAGE TRANSFER AGENT:SMTP
The actual mail transfer requires message transfer agents (MTAs).
The protocol that defines the MTA client and server in the Internet
is called Simple Mail Transfer Protocol (SMTP).

TCP/IP Protocol Suite 16
Responses

Connection establishment

Message transfer

Dcn ppt 150050705008

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