Web: Names and Addresses.


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empowers system switches to proficiently handle bundles in the Internet ... In 1998, non-benefit partnership, Internet Corporation for Assigned Names and ...
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Web: Names and Addresses

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Naming in the Internet What are named? All Internet Resources. Objects : www.cs.cornell.edu/pages/ranveer Services : weather.yahoo.com/conjecture Hosts : planetlab1.cs.cornell.edu Characteristics of Internet Names human unmistakable novel diligent Universal Resource Names (URNs)

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Locating the assets Internet administrations and assets are given by end-has ex. www1.cs.cornell.edu and www2.cs.cornell.edu host Ranveer\'s landing page. Names are mapped to Locations Universal Resource Locators (URL) Embedded in the name itself: ex. weather.yahoo.com/figure Semantics of Internet naming human unmistakable uniqueness tenacious

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Locating the assets Internet administrations and assets are given by end-has ex. www1.cs.cornell.edu and www2.cs.cornell.edu host Ranveer\'s landing page. Names are mapped to Locations Universal Resource Locators (URL) Embedded in the name itself: ex. weather.yahoo.com/figure Semantics of Internet naming human unmistakable uniqueness persevering

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Locating the Hosts? Web Protocol Addresses (IP Addresses) ex. planetlab1.cs.cornell.edu  128.84.154.49 Characteristics of IP Addresses 32 bit settled length empowers system switches to productively handle parcels in the Internet Locating administrations on hosts port numbers (16 bit unsigned whole number) 65536 ports standard ports: HTTP 80, FTP 20, SSH 22, Telnet 20

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Mapping Not 1 to 1 One host may guide to more than one name One server machine might be the web server (www.foo.com), mail server (mail.foo.com)etc. One host may have more than one IP address IP locations are per system interface But IP locations are by and large exceptional! two all inclusive noticeable machines ought not have the same IP address Anycast is an Exception : switches send bundles powerfully to the nearest have coordinating an anycast address

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How to get a name? Naming in Internet is Hierarchical reductions centralization enhances name space administration First, get an area name then you are allowed to relegate sub names in that space How to get an area name coming up Example: weather.yahoo.com has a place with yahoo.com which has a place with .com managed by worldwide non-benefit bodies

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Domain name structure root (anonymous) ... ... com edu gov mil net organization fr gr us uk ccTLDs gTLDs lucent cornell ustreas second level (sub-)areas gTLDs= Generic Top Level Domains ccTLDs = Country Code Top Level Domains

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Top-level Domains (TLDs) Generic Top Level Domains (gTLDs) .com - business associations .organization - not-revenue driven associations .edu - instructive associations .mil - military associations .gov - administrative associations .net - system administration suppliers New: .biz, .data, .name, … Country code Top Level Domains (ccTLDs) One for every nation

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How to get a space name? In 1998, non-benefit organization, Internet Corporation for Assigned Names and Numbers (ICANN), was shaped to expect obligation from the US Government ICANN approves different organizations to enlist areas in com, organization and net and new gTLDs Network Solutions is biggest and in transitional period between US Govt and ICANN had sole power to enlist spaces in com, organization and net

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How to get an IP Address? Answer 1: Normally, answer is get an IP address from your upstream supplier This is crucial to keep up productive steering! Answer 2: If you require heaps of IP addresses then you can obtain your own particular piece of them. IP address space is a rare asset - must demonstrate you have completely used a little piece before can request a bigger one and pay $$ (Jan 2002 - $2250/year for/20 and $18000/year for a/14)

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How to get heaps of IP Addresses? Web Registries RIPE NCC (Riseaux IP Europiens Network Coordination Center) for Europe, Middle-East, Africa APNIC (Asia Pacific Network Information Center )for Asia and Pacific ARIN (American Registry for Internet Numbers) for the Americas, the Caribbean, sub-saharan Africa Note: Once again local circulation is critical for proficient directing! Can likewise get Autonomous System Numnbers (ASNs from these registries

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Are there enough addresses? Sadly No! 32 bits  4 billion one of a kind addresses yet addresses are doled out in lumps ex. cornell has four lumps of/16 tended to ex. 128.84.0.0 to 128.84.255.255 128.253.0.0, 128.84.0.0, 132.236.0.0, and 140.251.0.0 Expanding the location space! IPv6 128 piece addresses hard to send (requires participation and changes to the center of the Internet)

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DHCP and NATs Dynamic Host Control Protocol lease IP addresses for brief time interims hosts may revive addresses intermittently just live has need substantial IP addresses Network Address Translators Hide neighborhood IP addresses from rest of the world just a little number of IP locations are obvious outside illuminates address lack for all down to earth purposes access is exceptionally confined ex. shared correspondence is troublesome

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NATs in operation Translate addresses when parcels cross through NATs Use port numbers to build number of supportable streams

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DNS: Domain Name System Domain Name System: appropriated database actualized in chain of command of numerous name servers application-layer convention host, switches, name servers to convey to determine names (address/name interpretation) note: center Internet capacity executed as application-layer convention many-sided quality at system\'s "edge"

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Name server: process running on a host that procedures DNS asks for nearby name servers: each ISP, organization has neighborhood (default) name server host DNS inquiry first goes to neighborhood name server definitive name server: can perform name/address interpretation for a particular space or zone How might we be able to give this administration? Why not incorporate DNS? single purpose of disappointment movement volume inaccessible brought together database upkeep doesn\'t scale! no server has all name-to-IP address mappings DNS name servers

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irs Zone : subtree with normal organization power. www Name Server Zone Structure root com gov edu mil net organization fr gr us uk lucent Structure taking into account managerial issues. ustreas

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ustreas traditions IRS NS Ustreas NS Lucent NS Root NS www Name Servers (NS) root com gov edu ... lucent cornell

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Name Servers (NS) NSs are copied for unwavering quality. Every space must have an essential and optional. Mysterious ftp from: ftp.rs.internic.net, netinfo/root-server.txt gives the present root NSs (around 10). Every host knows the IP location of the nearby NS. Every NS knows the IP locations of all root NSs.

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reached by nearby name server that can not resolve name root name server: Knows the legitimate name server for principle area ~ 60 root name servers overall true utilization of anycast DNS: Root name servers

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host surf.eurecom.fr needs IP location of www.cs.cornell.edu 1. Contacts its neighborhood DNS server, dns.eurecom.fr 2. dns.eurecom.fr contacts root name server, if essential 3. root name server contacts definitive name server, dns.cornell.edu, if essential (what may not be right with this?) nearby name server dns.eurecom.fr Simple DNS illustration root name server 2 4 3 5 authorititive name server dns.cornell.edu 1 6 asking for host surf.eurecom.fr www.cs.cornell.edu

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Root name server: may not know legitimate name server may know middle of the road name server: who to contact to discover legitimate name server neighborhood name server dns.eurecom.fr transitional name server dns.cornell.edu DNS sample root name server .edu name server 2 4 3 5 6 7 8 9 1 10 definitive name server dns.cs.cornell.edu asking for host surf.eurecom.fr www.cs.cornell.edu

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DNS Architecture Hierarchical Namespace Management spaces and sub-areas circulated and limited power Authoritative Nameservers server mappings for particular sub-areas more than one (no less than two for disappointment flexibility) Caching to moderate burden on root servers time-to-live (ttl) used to erase terminated reserved mappings

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iterated question: reached server answers with name of server to contact "I don\'t have a clue about this name, however ask this server" Takes load off root servers recursive inquiry: puts weight of name determination on reached name server diminishes dormancy nearby name server dns.eurecom.fr halfway name server dns.cornell.edu DNS: question determination root name server .edu name server iterated question 2 4 3 5 6 recursive question 9 8 7 1 10 legitimate name server dns.cs.cornell.edu asking for host surf.eurecom.fr www.cs.cornell.edu

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DNS: conveyed db putting away asset records (RR) Type=NS name is area (e.g. foo.com) quality is IP location of legitimate name server for this space RR group: (name, esteem, type,ttl) DNS records: More than Name to IP Address Type=CNAME name is a moniker name for a few "cannonical" (the genuine) name worth is cannonical name Type=A name is hostname worth is IP address One we\'ve been examining; most regular Type=MX quality is hostname of mailserver connected with name

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nslookup Use to inquiry DNS servers (not telnet like with http – why?) Examples: nslookup www.yahoo.com nslookup www.yahoo.com dns.cs.cornell.edu determine which neighborhood nameserver to utilize nslookup –type=mx cs.cornell.edu indicate record sort

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PTR Records Do switch mapping from IP location to name Why is that difficult? Which name server is in charge of that mapping? How would you discover them? Answer: extraordinary root area, arpa, for opposite lookups

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Arpa top level space Want to know machine name for 128.30.33.1? Issue a PTR ask for 1.33.30.128.in-addr.arpa root arpa com gov edu mil net organization fr gr us uk In-addr ietf www.ietf.org. www 128 30 33 1 1.33.30.128.in-addr.arpa.

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Why is it in reverse? Notice that 1.30.33.128.in-addr.arpa is composed in orde

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