ENVS 1000 Lecture Notes - Lecture 2: Web Browser, Hypertext Transfer Protocol
ENVS 1000 Lecture 2 Notes – Communication Channel
Introduction
• Messages to be shared by users and a communication channel to transport the
messages between users.
• There is a iplied protocol i this case also
• Namely, the assumption that both users share a common language which they both can
speak.
• For this example, there are also more subtle protocols that determine how the
connection is made and standards that establish the identities of the users in the form
of addresses o the telephoe etwork—or to be more specific, telephone numbers.
• Although these two examples seem superficial and simplistic, they do establish three
essential ingredients for data communication.
• First, the data being passed between sender and receiver represents messages that are
to be shared among the parties to the communications.
• Second, there must be a communication channel that can capably and reliably transport
the messages.
• Third, there must exist protocols that establish accurate and appropriate meaning to the
messages that are understood by both senders and receivers.
• The second example also raises the issues of connectivity methods and addressing.
• As a more realistic example of real-world data communication, consider the
communication between a Web browser and a Web server.
• In this case, the message sent by the browser is a request for a Web page to be sent by
the server.
• Assuming that everything works correctly, the response message by the server is a Web
page to be displayed on the browser.
• The standard protocol used for this communication is HTTP, hypertext transfer protocol.
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