02app_pt2 - DNS, P2P, socket programming 01 Feb 2011 CSCD58...

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Unformatted text preview: DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 1 02apps_pt2 CSCD58S Computer Networks 1 Chapter 2 roadmap b 2.1 Principles of app layer protocols c clients and servers c app requirements b 2.2 Web and HTTP b 2.3 FTP b 2.4 Electronic Mail c SMTP, POP3, IMAP b 2.5 DNS b 2.6 P2P applications b 2.8 Socket programming with TCP b 2.7 Socket programming with UDP DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 2 02apps_pt2 CSCD58S Computer Networks 2 DNS: Domain Name System b Flat namespace c /etc/hosts.txt; where? downloads? updates? b distributed database implemented in hierarchy of many name servers c Goals b Scalability b Decentralized maintenance b Robustness, fault-tolerance b Global scope: names mean the same thing everywhere b Dont need c Atomicity c Strong consistency c Why not a centralized DNS? b scalability, hard to maintain, single point of failure b application-layer protocol used by hosts and name servers c core Internet function, implemented as app-layer protocol (!) b complexity at networks edge DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 3 02apps_pt2 CSCD58S Computer Networks 3 DNS: Domain Name System People: many identifiers: c SIN, name, passport # Internet hosts, routers: c IP address (32 bit) - used for addressing datagrams c name, e.g., www.yahoo.com - used by humans Q: map between IP addresses and name ? Domain Name System: b distributed database implemented in hierarchy of many name servers b application-layer protocol host, routers, name servers to communicate to resolve names (address/name translation) c note: core Internet function, implemented as application-layer protocol c complexity at networks edge DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 4 02apps_pt2 CSCD58S Computer Networks 4 DNS DNS Why not centralize DNS? b single point of failure b traffic volume b distant centralized database b maintenance / updates? doesnt scale! DNS services b hostname to IP address translation b host aliasing c canonical + alias names c e.g. www.utoronto.ca b mail server aliasing c e.g. utsc.utoronto.ca b load distribution c replicated Web servers: set of IP addresses for one canonical name c e.g. www.google.com 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 DNS servers Distributed, Hierarchical Database Distributed, Hierarchical Database Client wants IP for www.amazon.com; 1 st approx: b client queries a root server to find .com DNS server b client queries .com DNS server to get amazon.com DNS server b client queries amazon.com DNS server to get IP address for www.amazon.com DNS, P2P, socket programming 01 Feb 2011 CSCD58 Computer Networks 6 02apps_pt2 CSCD58S Computer Networks 7 DNS: Root name servers DNS: Root name servers...
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This note was uploaded on 02/05/2011 for the course CS 58 taught by Professor Alanrosselet during the Winter '11 term at University of Toronto- Toronto.

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02app_pt2 - DNS, P2P, socket programming 01 Feb 2011 CSCD58...

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