This document discusses the Hypertext Transfer Protocol (HTTP) which defines how messages are formatted and transmitted on the World Wide Web. It establishes HTTP as the foundation of data communication, outlining the request/response format and various methods like GET and POST. The document also compares versions HTTP 1.0 and 1.1, covering persistent connections, pipelining, cookies, caching improvements, and other features. It provides details on HTTPS which uses HTTP over SSL to securely transmit encrypted data and authenticate web servers.

1. Hypertext
Transfer Protocol
Internet Engineering Task
Force (IETF) and the World
Wide Web Consortium (W3C)

2. Topics
What is HTTP
Why HTTP
HTTP 1.0 vs. HTTP 1.1
Request/Response formats and header
HTTP methods
HTTP Status Codes
Session maintenance
What is HTTPS
SSL Handshake

3. • Foundation of data communication
for the World Wide Web
Defines how messages are
formatted and transmitted
What actions web servers and
browsers should take in response
to various commands
Ted Nelson
Vannevar Bush's-memex
Tim Berners-Lee- CERN

4. Why Http?
 To transfer hypertext(linked) data over WWW
 Request/response stateless protocol that can
be used widely.

5. HTTP?
 Functions as a request-response protocol in
the client-server computing model.
 Application layer protocol.
 Stateless protocol.
 TCP connection.
 Uses URL addressing
 Method request
 Response codes
 Uses Caching and conditional get
 Session maintenance

6. HTTP versions 1.0 vs 1.1
 Persistent Connections
 Pipelining
 State management(cookies)
 Compression
 Range requests
 Caching

7. HTTP versions 1.0 vs 1.1
 Persistent Connections : TCP connection to send and
receive multiple HTTP requests/responses as opposed to opening a
new connection for every single request/response pair
 Pipelining

8. HTTP versions 1.0 vs 1.1
 State management(cookies):
 Netscape introduced cookies
 Compression:
 compression could save almost 40% of the bytes sent via HTTP
 content-coding or as a transfer-coding
 Accept-Encoding header
 Range requests: A client may need only part of a resource range
requests allow a client to request portions of a resource
 To complete a response transfer that was interrupted (either by the user or
by a network failure)

9. HTTP versions 1.0 vs 1.1
 Caching: to store locally for faster access
Caching in HTTP/1.0
 Check validity by conditional request ( If-Modified-Since)
Replying 304 (Not Modified) or 200 (OK)
 No Cache control (incorrect caching and failure to cache)
Caching in HTTP/1.1
 Opaque cache validator string- Entity tag(caching errors either because of
clock synchronization errors, or because of lack of resolution)
 New conditional request-headers: If-None-Match, If-Unmodified-
Since and If-Match
 Cache-Control header : public, private, no-store, no-cache

10. HTTP request and response
HTTP Response format
HTTP Request format

12. HTTP Methods
 Methods are commands to server for request or
command

13. Method classified as:
 Safe Methods: Do not modify resources-
retrieval only
 Idempotent Method: Can be called many
times , same outcome

14. Get, Put and Post
 Get: GET method means retrieve whatever
information is identified by the Request-URI.
 Conditional Get : If-Modified-Since, If-Unmodified-Since, If-Match, If-None-
Match
 Partial Get : Range header field.
**Response to GET request is cacheable
 PUT: PUT method requests that the enclosed entity
be stored under the supplied Request-URI
 If a new resource is created server responsed 201 (Created).
 Responses to PUT method are not cacheable

15.  POST: POST method requests that a web server accepts and
stores/processes the data enclosed in the body of the request
message.
 Function of POST method is determined by the server and is
dependent on the Request-URI
** GET requests data from a specified resource POST submits data
to be processed to a specified resource
**PUT is like a file upload. A put to a URI affects exactly that URI. A
POST to a URI could have any effect at all.

16. HTTP Status Codes
• This class of status code indicates a
provisional response

17. Cookies
 Sessions are used for maintaining user specific state
and authenticated user identities, among many
interactions
 privacy and security implications

18. HTTPS
 HTTP over SSL
 port 443
 HTTPS is authentication web server and to protect
the privacy and integrity of the exchanged data.

19. SSL/TSL
 TCP & SSL: provides a reliable & secure
end-to-end service.
 Uses Public private key to encrypt
 Asymmetric then symmetric
 Key exchange(Deffie-hellman), Cipher (AES),
Hash(MD5), Version, random number
 Ensures confidentiality, Message intergrity
and key Authentication.
SSL originally developed by Netscape