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02app_pt2 - DNS P2P socket programming 01 Feb 2011 Chapter...

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DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 1 02apps_pt2 CSCD58S Computer Networks 1 Chapter 2 roadmap boxshadowdwn 2.1 Principles of app layer protocols circleshadowdwn clients and servers circleshadowdwn app requirements boxshadowdwn 2.2 Web and HTTP boxshadowdwn 2.3 FTP boxshadowdwn 2.4 Electronic Mail circleshadowdwn SMTP, POP3, IMAP boxshadowdwn 2.5 DNS boxshadowdwn 2.6 P2P applications boxshadowdwn 2.8 Socket programming with TCP boxshadowdwn 2.7 Socket programming with UDP
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DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 2 02apps_pt2 CSCD58S Computer Networks 2 DNS: Domain Name System boxshadowdwn Flat namespace circleshadowdwn /etc/hosts.txt; where? downloads? updates? boxshadowdwn distributed database implemented in hierarchy of many name servers circleshadowdwn Goals boxshadowdwn Scalability boxshadowdwn Decentralized maintenance boxshadowdwn Robustness, fault-tolerance boxshadowdwn Global scope: names mean the same thing everywhere boxshadowdwn Don’t need circleshadowdwn Atomicity circleshadowdwn Strong consistency circleshadowdwn Why not a centralized DNS? boxshadowdwn scalability, hard to maintain, single point of failure boxshadowdwn application-layer protocol used by hosts and name servers circleshadowdwn core Internet function, implemented as app-layer protocol (!) boxshadowdwn complexity at network’s “edge”
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DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 3 02apps_pt2 CSCD58S Computer Networks 3 DNS: Domain Name System People: many identifiers: circleshadowdwn SIN, name, passport # Internet hosts, routers: circleshadowdwn IP address (32 bit) - used for addressing datagrams circleshadowdwn “name”, e.g., www.yahoo.com - used by humans Q: map between IP addresses and name ? Domain Name System: boxshadowdwn distributed database implemented in hierarchy of many name servers boxshadowdwn application-layer protocol host, routers, name servers to communicate to resolve names (address/name translation) circleshadowdwn note: core Internet function, implemented as application-layer protocol circleshadowdwn complexity at network’s “edge”
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DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 4 02apps_pt2 CSCD58S Computer Networks 4 DNS DNS Why not centralize DNS? boxshadowdwn single point of failure boxshadowdwn traffic volume boxshadowdwn distant centralized database boxshadowdwn maintenance / updates? doesn’t scale! DNS services boxshadowdwn hostname to IP address translation boxshadowdwn host aliasing circleshadowdwn canonical + alias names circleshadowdwn e.g. www.utoronto.ca boxshadowdwn mail server aliasing circleshadowdwn e.g. utsc.utoronto.ca boxshadowdwn load distribution circleshadowdwn replicated Web servers: set of IP addresses for one canonical name circleshadowdwn e.g. www.google.com
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DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 5 02apps_pt2 CSCD58S Computer Networks 5 Root DNS Servers com DNS servers org DNS servers edu DNS servers cmu.edu DNS servers toronto.edu DNS servers yahoo.com DNS servers amazon.com DNS servers pbs.org
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