1 COMP 431 Internet Services & Protocols Application-Layer Protocols: The Web & HTTP Jasleen Kaur January 28, 2020 2 Application-Layer Protocols Outline ◆ Example client/server systems and their application-level protocols: » The World-Wide Web (HTTP) » Reliable file transfer (FTP) » E-mail (SMTP & POP) » Internet Domain Name System (DNS) ◆ Example p2p applications systems: » BitTorrent ◆ Other protocols and systems: » Streaming media — DASH » Content delivery networks (CDNs) transport network link physical application regional ISP Institutional network
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COMP 431Internet Services & Protocols
Application-Layer Protocols:The Web & HTTP
Jasleen Kaur
January 28, 2020
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Application-Layer ProtocolsOutline
◆ Example client/server systems and their application-level protocols:» The World-Wide Web (HTTP)» Reliable file transfer (FTP)» E-mail (SMTP & POP)» Internet Domain Name System (DNS)
◆ Example p2p applications systems:» BitTorrent
◆ Other protocols and systems:» Streaming media — DASH» Content delivery networks (CDNs)
applicationtransportnetwork
linkphysical
application
regional ISP
Institutional network
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Applications and Application-Layer ProtocolsOverview
◆ Applications: » Communicating, distributed
processes» Running in network hosts in “user
space”» Exchange messages
◆ Application-layer protocols» One “piece” of an application» Defines messages exchanged and
actions taken» Uses services provided by lower
layer protocols
mobile network
global ISP
regional ISP
home network
Institutional network
applicationtransportnetwork
linkphysical
application
applicationtransportnetwork
linkphysical
application
applicationtransportnetwork
linkphysical
application
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Application-Layer ProtocolsThe Web
◆ User agent (client) for the Web is called a browser:» MS Internet Explorer» Google Chrome» Apple Safari» Mozilla Firefox
◆ Server for the Web is called a Web server:» Apache (public domain)» MS Internet Information Server (IIS)
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Application-Layer ProtocolsWeb Terminology
◆ Web page:» Addressed by a URL» Consists of “objects”
◆ Most Web pages consist of:» Base HTML page» Embedded objects<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html lang="en"><head>