Persistent vs Non-Persistent HTTP Connections
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Persistent vs Non-Persistent HTTP Connections

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@AwestruckYew

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Questions and Answers

What HTTP response status code indicates that the requested object has been moved to a new location?

  • 200 OK
  • 404 Not Found
  • 301 Moved Permanently (correct)
  • 400 Bad Request

    • In the context of HTTP, what does a 404 status code signify?

  • Requested document not found on this server (correct)
  • Request succeeded
  • Request message not understood by server
  • Requested object later in this message

    • When establishing a TCP connection to an HTTP server, what is the default port used?

  • 80 (correct)
  • 8080
  • 443
  • 53

    • What does a 400 status code signify in the context of HTTP?

    <p>Request message not understood by server</p> Signup and view all the answers

    Which HTTP version is mentioned in the request message 'GET /fee/NewsDetails/142317/en HTTP/1.1'?

    <p>HTTP/1.1</p> Signup and view all the answers

    What does sending a minimal GET request involve in terms of communication with an HTTP server?

    <p>Sending a minimal but complete request via port 80</p> Signup and view all the answers

    Which status code indicates that the HTTP version used in the request is not supported?

    <p>505 HTTP Version Not Supported</p> Signup and view all the answers

    'ncat www.menofia.edu.eg 80' is an example of what kind of connection in the context of HTTP?

    <p>'Persistent' connection</p> Signup and view all the answers

    'GET /fee/NewsDetails/142317/en HTTP/1.1' is an example of what part of an HTTP transaction?

    <p>'Request message'</p> Signup and view all the answers

    'Host: www.menofia.edu.eg' is typically found in which part of an HTTP request message?

    <p>'Request header'</p> Signup and view all the answers

    Study Notes

    HTTP Protocol

    • Past history (state) must be maintained, and reconciled in case of server/client crashes
    • HTTP connections have two types: non-persistent and persistent

    Non-Persistent HTTP

    • One TCP connection is opened and closed for each object
    • Example: user enters URL www.someSchool.edu/someDepartment/home.index containing text and references to 10 jpeg images
    • Steps:
      • HTTP client initiates TCP connection to HTTP server at port 80
      • HTTP client sends HTTP request message containing URL
      • HTTP server receives request message, forms response message, and sends message into its socket
      • HTTP server closes TCP connection
    • This process is repeated for each of the 10 jpeg objects
    • RTT (Round Trip Time) is the time for a small packet to travel from client to server and back
    • HTTP response time per object: 2RTT + file transmission time

    Issues with Non-Persistent HTTP

    • Requires 2 RTTs per object
    • OS overhead for each TCP connection
    • Browsers often open multiple parallel TCP connections to fetch referenced objects in parallel

    Persistent HTTP (HTTP 1.1)

    • Server leaves connection open after sending response
    • Subsequent HTTP messages between same client/server are sent over open connection
    • Client sends requests as soon as it encounters a referenced object
    • Response time is reduced to as little as one RTT for all referenced objects

    HTTP Request and Response Messages

    • Two types of HTTP messages: request and response
    • HTTP request message:
      • ASCII (human-readable format)
      • Request line (GET, POST, HEAD commands)
      • Header lines
    • HTTP response message:
      • Status codes (e.g. 200 OK, 301 Moved Permanently, 400 Bad Request, 404 Not Found, 505 HTTP Version Not Supported)

    Trying out HTTP (Client Side)

    • Use ncat tool to connect to a web server (e.g. www.menofia.edu.eg)
    • Type in a GET HTTP request message (e.g. GET /fee/NewsDetails/142317/en HTTP/1.1)
    • Observe the response message sent by the HTTP server

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    Description

    Learn about the differences between persistent and non-persistent HTTP connections in this quiz. Explore how maintaining the past history (state) is crucial, and how to reconcile inconsistent views of 'state' when servers or clients crash.

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