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    Networks - W3

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    Networks - W3

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    toti5824
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    Copyright:

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    Download as pptx, pdf, or txt
    3 views24 pages

    Networks - W3

    Uploaded by

    toti5824

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 24

    COMPUTER NETWORKS

    ( 00207N )

    Week 3
    Topics

    ■ HTTP Definition
    ■ HTTP vs HTTPS
    ■ HTTP Message Types
    ■ Wireshark Overview
    ■ Basic HTTP GET/response interaction
    ■ HTTP CONDITIONAL GET/response interaction
    ■ Retrieving Long Documents
    ■ HTTP Authentication
    ■ Authentication (Wireshark)
    ■ Reference
    HTTP Definition

    ■ HTTP stands for Hypertext Transfer Protocol used for transferring data over a network.
    Most information that is sent over the Internet, including website content and API calls,
    uses the HTTP protocol.
    – There are two main kinds of HTTP messages: requests and responses.
    HTTP vs HTTPS Protocols
    HTTP Message Types
    HTTP Request message
    HTTP Response Message
    HTTP Overview

    http://www.mit.edu
    Wireshark Overview
    Wireshark Overview
    Basic HTTP GET/response interaction

    ■ URL : http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file1.html
    ■ Operation 1 , Steps:
    – Start Wireshark
    – Load above URL
    – Stop Wireshark
    Basic HTTP GET/response interaction

    ■ 1. Is your browser running HTTP version 1.0 or 1.1? What version of HTTP is the
    server running?
    ■ 2. What languages (if any) does your browser indicate that it can accept to the server?
    ■ 3. What is the IP address of your computer? Of the gaia.cs.umass.edu server?
    ■ 4. What is the status code returned from the server to your browser?
    Basic HTTP GET/response interaction

    ■ 5. When was the HTML file that you are retrieving last modified at the server?
    – Must clear cache of the browser
    ■ 6. How many bytes of content are being returned to your browser?
    ■ 7. By inspecting the raw data in the packet content window, do you see any headers
    within the data that are not displayed in the packet-listing window? If so, name one.
    HTTP CONDITIONAL GET/response
    interaction
    ■ URL : http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file2.html
    ■ Operation 2 , Steps:
    – Clear your browser cache
    – Start Wireshark
    – Load above URL twice
    – Stop Wireshark
    HTTP CONDITIONAL GET/response
    interaction
    HTTP CONDITIONAL GET/response
    interaction
    ■ 1. Inspect the contents of the first HTTP GET request from your browser to the server.
    Do you see an “IF-MODIFIED-SINCE” line in the HTTP GET?
    ■ 2. Inspect the contents of the server response. Did the server explicitly return the
    contents of the file? How can you tell?
    ■ 3. Now inspect the contents of the second HTTP GET request from your browser to the
    server. Do you see an “IF-MODIFIED-SINCE:” line in the HTTP GET? If so, what
    information follows the “IF-MODIFIED-SINCE:” header?
    ■ 4. What is the HTTP status code and phrase returned from the server in response to this
    second HTTP GET? Did the server explicitly return the contents of the file? Explain.
    Retrieving Long Documents

    ■ URL : http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html
    ■ Operation 3 , Steps:
    – Clear your browser cache
    – Start Wireshark
    – Load above URL
    – Stop Wireshark
    Retrieving Long Documents

    ■ 1. How many HTTP GET request messages did your browser send? Which packet
    number in the trace contains the GET message for the Bill of Rights?
    ■ 2. Which packet number in the trace contains the status code and phrase associated with
    the response to the HTTP GET request?
    ■ 3. What is the status code and phrase in the response?
    ■ 4. How many data-containing TCP segments were needed to carry the single HTTP
    response and the text of the Bill of Rights?
    HTTP Authentication

    ■ URL : http://gaia.cs.umass.edu/wireshark-labs/protected_pages/HTTP-wireshark-
    file5.html
    ■ Operation 5 , Steps:
    – Clear your browser cache
    – Start Wireshark
    – Load above URL
    – Username : wireshark-students , Password : network
    – Stop Wireshark
    HTTP Authentication

    ■ 1. What is the server’s response (status code and phrase) in response to the initial HTTP
    GET message from your browser?
    ■ 2. When your browser’s sends the HTTP GET message for the second time, what new
    field is included in the HTTP GET message?
    Revision (HTTP vs HTTPS Protocols)
    Authentication (Wireshark)
    ■ HTTP
    Authentication (Wireshark)
    ■ HTTPS
    – We can’t sniff it with Wireshark using normal methods because it’s encrypted
    – This is how it looks like if we tried to do it normally :
    Reference

    ■ https://www-net.cs.umass.edu/wireshark-labs/Wireshark_HTTP_v7.0.pdf

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