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Lab Exercise – HTTP
Objective
HTTP (HyperText Transfer Protocol) is the main protocol underlying the Web. HTTP functions as a re-
quest–response protocol in the client–server computing model. A web browser, for example, may be the
client and an application running on a computer hosting a website may be the server. The client submits
an HTTP request message to the server. The server, which provides resources such as HTML files and other
content, or performs other functions on behalf of the client, returns a response message to the client. The
response contains completion status information about the request and may also contain requested con-
tent in its message body. A web browser is an example of a user agent (UA). Other types of user agent
include the indexing software used by search providers (web crawlers), voice browsers, mobile apps, and
other software that accesses, consumes, or displays web content. HTTP is designed to permit intermediate
network elements to improve or enable communications between clients and servers. High-traffic web-
sites often benefit from web cache servers that deliver content on behalf of upstream servers to improve
response time. Web browsers cache previously accessed web resources and reuse them when possible to
reduce network traffic. HTTP is an application layer protocol designed within the framework of the Inter-
net protocol suite. Its definition presumes an underlying and reliable transport layer protocol and Trans-
mission Control Protocol (TCP) is commonly used.
Step 1: Open the http Trace
Browser behavior can be quite complex, using more HTTP features than the basic exchange, this trace
will show us how much gets transferred.
1. Open the trace file from here: https://kevincurran.org/com320/labs/wireshark/trace-http.pcap
You should then see a Wireshark screen like below.
Figure 1: The Wireshark screen after opening the http trace file