Chapter 7 The Application Layer DNS The Domain Name System The - - PowerPoint PPT Presentation

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Chapter 7 The Application Layer DNS The Domain Name System The - - PowerPoint PPT Presentation

Dec 06, 2023 477 likes •1.39k views

Chapter 7 The Application Layer 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

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The Application Layer

Chapter 7

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DNS – The Domain Name System

  • The DNS Name Space
  • Resource Records
  • Name Servers
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The DNS Name Space

A portion of the Internet domain name space.

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Resource Records

The principal DNS resource records types.

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Resource Records (2)

A portion of a possible DNS database for cs.vu.nl.

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Name Servers

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

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Name Servers (2)

How a resolver looks up a remote name in eight steps.

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Electronic Mail

  • Architecture and Services
  • The User Agent
  • Message Formats
  • Message Transfer
  • Final Delivery
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Electronic Mail (2)

Some smileys. They will not be on the final exam :-).

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Architecture and Services

Basic functions

  • Composition
  • Transfer
  • Reporting
  • Displaying
  • Disposition
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The User Agent

Envelopes and messages. (a) Paper mail. (b) Electronic mail.

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Reading E-mail

An example display of the contents of a mailbox.

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Message Formats – RFC 822

RFC 822 header fields related to message transport.

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Message Formats – RFC 822 (2)

Some fields used in the RFC 822 message header.

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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).

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MIME (2)

RFC 822 headers added by MIME.

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MIME (3)

The MIME types and subtypes defined in RFC 2045.

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MIME (4)

A multipart message containing enriched and audio alternatives.

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Message Transfer

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

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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.

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POP3

Using POP3 to fetch three messages.

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IMAP

A comparison of POP3 and IMAP.

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The World Wide Web

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

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

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Architectural Overview (2)

The parts of the Web model.

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The Client Side

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

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The Server Side

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

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The Server Side (2)

A server farm.

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The Server Side (3)

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

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URLs – Uniform Resource Locaters

Some common URLs.

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Statelessness and Cookies

Some examples of cookies.

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HTML – HyperText Markup Language

(a) The HTML for a sample Web page. (b) The formatted page.

(b)

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HTML (2)

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

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Forms

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

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Forms (2)

(a) The HTML for an

  • rder form.

(b) The formatted page.

(b)

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Forms (3)

A possible response from the browser to the server with information filled in by the user.

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XML and XSL

A simple Web page in XML.

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XML and XSL (2)

A style sheet in XSL.

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Dynamic Web Documents

Steps in processing the information from an HTML form.

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Dynamic Web Documents (2)

A sample HTML page with embedded PHP.

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Dynamic Web Documents (3)

(a) A Web page containing a form. (b) A PHP script for handling the

  • utput of the form. (c) Output from the PHP script when the inputs

are "Barbara" and 24 respectively.

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Client-Side Dynamic Web Page Generation

Use of JavaScript for processing a form.

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Client-Side Dynamic Web Page Generation (2)

(a) Server-side scripting with PHP. (b) Client-side scripting with JavaScript.

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Client-Side Dynamic Web Page Generation (3)

A JavaScript program for computing and printing factorials.

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Client-Side Dynamic Web Page Generation (4)

An interactive Web page that responds to mouse movement.

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Client-Side Dynamic Web Page Generation (5)

The various ways to generate and display content.

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HTTP Methods

The built-in HTTP request methods.

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HTTP Methods (2)

The status code response groups.

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HTTP Message Headers

Some HTTP message headers.

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Example HTTP Usage

The start of the output of www.ietf.org/rfc.html.

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Caching

Hierarchical caching with three proxies.

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Content Delivery Networks

(a) Original Web page. (b) Same page after transformation.

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The Wireless Web

Steps in looking up a URL when a CDN is used.

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WAP – The Wireless Application Protocol

The WAP protocol stack.

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WAP (2)

The WAP architecture.

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I-Mode

Structure of the i-mode data network showing the transport protocols.

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I-Mode (2)

Structure of the i-mode software.

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I-Mode (3)

Lewis Carroll meets a 16 x 16 screen.

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I-Mode (4)

An example of cHTML file.

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Second-Generation Wireless Web

A comparison of first-generation WAP and i-mode.

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Second-Generation Wireless Web (2)

New features of WAP 2.0.

  • Push model as well as pull model.
  • Support for integrating telephony into apps.
  • Multimedia messaging.
  • Inclusion of 264 pictograms.
  • Interface to a storage device.
  • Support for plug-ins in the browser.
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Second-Generation Wireless Web (3)

WAP 2.0 supports two protocol stacks.

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Second-Generation Wireless Web (4)

The XHTML Basic modules and tags.

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Multimedia

  • Introduction to Audio
  • Audio Compression
  • Streaming Audio
  • Internet Radio
  • Voice over IP
  • Introduction to Video
  • Video Compression
  • Video on Demand
  • The MBone – The Multicast Backbone
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Introduction to Audio

(a) A sine wave. (b) Sampling the sine wave. (c) Quantizing the samples to 4 bits.

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Audio Compression

(a) The threshold of audibility as a function of frequency. (b) The masking effect.

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Streaming Audio

A straightforward way to implement clickable music on a Web page.

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Streaming Audio (2)

When packets carry alternate samples, the loss of a packet reduces the temporal resolution rather than creating a gap in time.

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Streaming Audio (3)

The media player buffers input from the media server and plays from the buffer rather than directly from the network.

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Streaming Audio (4)

RTSP commands from the player to the server.

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Internet Radio

A student radio station.

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Voice over IP

The H323 architectural model for Internet telephony.

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Voice over IP (2)

The H323 protocol stack.

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Voice over IP (3)

Logical channels between the caller and callee during a call.

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SIP – The Session Initiation Protocol

The SIP methods defined in the core specification.

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SIP (2)

Use a proxy and redirection servers with SIP.

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Comparison of H.323 and SIP

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Video Analog Systems

The scanning pattern used for NTSC video and television.

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The JPEG Standard

The operation of JPEG in lossy sequential mode.

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The JPEG Standard (2)

(a) RGB input data. (b) After block preparation.

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The JPEG Standard (3)

(a) One block of the Y matrix. (b) The DTC coefficients. (a) (b)

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The JPEG Standard (4)

Computation of the quantized DTC coefficients.

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The JPEG Standard (5)

The order in which the quantized values are transmitted.

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The MPEG Standard

Synchronization of the audio and video streams in MPEG-1.

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The MPEG Standard (2)

Three consecutive frames.

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Video on Demand

Overview of a video-on-demand system.

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Video Servers

A video server storage hierarchy.

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Video Servers (2)

The hardware architecture of a typical video server.

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The MBone – The Multicast Backbone

MBone consists of multicast islands connected by tunnels.