the network layers for the understanding

DNS – The Domain Name System
• The DNS Name Space
• Resource Records
• Name Servers

The DNS Name Space
A portion of the Internet domain name space.

Resource Records
The principal DNS resource records types.

Resource Records (2)
A portion of a possible DNS database for cs.vu.nl.

Name Servers
Part of the DNS name space showing the division into zones.

Name Servers (2)
How a resolver looks up a remote name in eight steps.

Electronic Mail
• Architecture and Services
• The User Agent
• Message Formats
• Message Transfer
• Final Delivery

Electronic Mail (2)
Some smileys. They will not be on the final exam :-).

Architecture and Services
Basic functions
• Composition
• Transfer
• Reporting
• Displaying
• Disposition

The User Agent
Envelopes and messages. (a) Paper mail. (b) Electronic mail.

Reading E-mail
An example display of the contents of a mailbox.

Message Formats – RFC 822
RFC 822 header fields related to message transport.

Message Formats – RFC 822 (2)
Some fields used in the RFC 822 message header.

MIME – Multipurpose Internet Mail
Extensions
Problems with international languages:
• Languages with accents
(French, German).
• Languages in non-Latin alphabets
(Hebrew, Russian).
• Languages without alphabets
(Chinese, Japanese).
• Messages not containing text at all
(audio or images).

MIME (2)
RFC 822 headers added by MIME.

MIME (3)
The MIME types and subtypes defined in RFC 2045.

MIME (4)
A multipart message containing enriched and audio alternatives.

Message Transfer
Transferring a message
from
elinore@abc.com to
carolyn@xyz.com.

Final Delivery
(a) Sending and reading mail when the receiver has a permanent
Internet connection and the user agent runs on the same machine as
the message transfer agent. (b) Reading e-mail when the receiver has
a dial-up connection to an ISP.

POP3
Using POP3 to fetch three messages.

IMAP
A comparison of POP3 and IMAP.

The World Wide Web
• Architectural Overview
• Static Web Documents
• Dynamic Web Documents
• HTTP – The HyperText Transfer Protocol
• Performance Ehnancements
• The Wireless Web

Architectural
Overview
(a) A Web page (b) The page reached by clicking on
Department of Animal Psychology.

Architectural Overview (2)
The parts of the Web model.

The Client Side
(a) A browser plug-in. (b) A helper application.

The Server Side
A multithreaded Web server with a front end and processing modules.

The Server Side (2)
A server farm.

The Server Side (3)
(a) Normal request-reply message sequence.
(b) Sequence when TCP handoff is used.

URLs – Uniform Resource Locaters
Some common URLs.

Statelessness and Cookies
Some examples of cookies.

HTML – HyperText Markup Language
(a) The HTML for a sample Web page. (b) The formatted page.
(b)

HTML (2)
A selection of common HTML tags.
some can have additional parameters.

Forms
(a) An HTML table.
(b) A possible rendition of this
table.

Forms (2)
(a) The HTML for an
order form.
(b) The formatted page.
(b)

Forms (3)
A possible response from the browser to the server with information
filled in by the user.

XML and XSL
A simple Web page
in XML.

XML and XSL (2)
A style sheet in
XSL.

Dynamic Web Documents
Steps in processing the information from an HTML form.

Dynamic Web Documents (2)
A sample HTML page with embedded PHP.

Dynamic Web
Documents (3)
(a) A Web page containing a form. (b) A PHP script for handling the
output of the form. (c) Output from the PHP script when the inputs
are "Barbara" and 24 respectively.

Client-Side Dynamic Web Page Generation
Use of JavaScript
for processing a
form.

Client-Side Dynamic Web Page Generation (2)
(a) Server-side scripting with PHP.
(b) Client-side scripting with JavaScript.

the network layers for the understanding

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