1 developed browserserver persistent connec8ons

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Unformatted text preview: org. Snapshot on 27.02.12. Does not represent current deployment. 118 DNS Protocol •  Query and response messages –  Built on UDP messages, port 53 –  ARQ for reliability; server is stateless! –  Messages linked by a 16- bit ID field Client Query Server ID=0x1234 Time ID=0x1234 Response 119 13 11/26/13 DNS Protocol (2) •  Service reliability via replicas –  Run mul8ple nameservers for domain –  Return the list; clients use one answer –  Helps distribute load too NS for uw.edu? Use A, B or C A B C 120 DNS Protocol (3) •  Security is a major issue –  Compromise redirects to wrong site! –  Not part of ini8al protocols .. •  DNSSEC (DNS Security Extensions) –  Long under development, now par8ally deployed. We’ll look at it later Um, security?? 121 14 11/26/13 Introduc8on to Computer Networks HTTP, the HyperText Transfer Protocol (§7.3.1- 7.3.4) Computer Science & Engineering Topic •  HTTP, (HyperText Transfer Protocol) –  Basis for fetching Web pages request Network 123 15 11/26/13 Web Context Page as a set of related HTTP transac8ons HTTP request HTTP response 124 Web Protocol Context •  HTTP is a request/response protocol for fetching Web resources –  Runs on TCP, typically port 80 –  Part of browser/server app browser HTTP TCP IP 802.11 request response server HTTP TCP IP 802.11 125 16 11/26/13 Fetching a Web page with HTTP •  Start with the page URL: hfp://en.wikipedia.org/wiki/Vegemite Protocol Server Page on server •  Steps: –  Resolve the server to IP address (DNS) –  Set up...
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This document was uploaded on 04/04/2014.

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