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0212 does not represent current deployment 118 dns

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Unformatted text preview: lver) for manageability –  Lets server cache over a pool of clients for befer performance •  Itera8ve query –  Lets server “file and forget” –  Easy to build high load servers 113 10 11/26/13 Caching •  Resolu8on latency should be low –  Adds delay to web browsing •  Cache query/responses to answer future queries immediately –  Including par8al (itera8ve) answers –  Responses carry a TTL for caching query Cache response out Nameserver 114 Caching (2) •  flits.cs.vu.nl now resolves eng.washington.edu –  And previous resolu8ons cut out most of the process I know the server for washington.edu! 1: query 2: query Cache 4: eng.washington.edu 3: eng.washington.edu Local nameserver (for cs.vu.nl) UW nameserver (for washington.edu) 115 11 11/26/13 Local Nameservers •  Local nameservers typically run by IT (enterprise, ISP) –  But may be your host or AP –  Or alterna8ves e.g., Google public DNS •  Clients need to be able to contact their local nameservers –  Typically configured via DHCP 116 Root Nameservers •  Root (dot) is served by 13 server names –  a.root- servers.net to m.root- servers.net –  All nameservers need root IP addresses –  Handled via configura8on file (named.ca) •  There are >250 distributed server instances –  Highly reachable, reliable service –  Most servers are reached by IP anycast (Mul8ple loca8ons adver8se same IP! Routes take client to the closest one. See §5.x.x) –  Servers are IPv4 and IPv6 reachable 117 12 11/26/13 Root Server Deployment Source: hfp://www.root- servers....
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