computer networks
DESCRIPTION
Computer Networks. NYUS FCSIT Spring 2008 Milos STOLIC, Bs.C. Teaching Assistant [email protected]. The Application Layer. Chapter 7. 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. - PowerPoint PPT PresentationTRANSCRIPT
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The Application Layer
Chapter 7
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DNS – The Domain Name System
a) The DNS Name Space
b) Resource Records
c) 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
a) Architecture and Services
b) The User Agent
c) Message Formats
d) Message Transfer
e) 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 functionsa) Composition
b) Transfer
c) Reporting
d) Displaying
e) 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:
a) Languages with accents (French, German).
b) Languages in non-Latin alphabets (Hebrew, Russian).
c) Languages without alphabets (Chinese, Japanese).
d) 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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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
a) Architectural Overview
b) Static Web Documents
c) Dynamic Web Documents
d) HTTP – The HyperText Transfer Protocol
e) Performance Ehnancements
f) 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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HTTP Methods
The built-in HTTP request methods.
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HTTP Methods (2)
The status code response groups.
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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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The Wireless Web
Steps in looking up a URL when a CDN is used.
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Multimediaa) Introduction to Audio
b) Streaming Audio
c) Internet Radio
d) Voice over IP
e) Introduction to Video
f) Video Compression
g) Video on Demand
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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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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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Video Analog Systems
The scanning pattern used for NTSC video and television.
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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.