{"licence":{"name":"CC BY-SA 4.0","spdx":"CC-BY-SA-4.0","url":"https://creativecommons.org/licenses/by-sa/4.0/","attribution":"Atlas, a bilingual technical dictionary (https://cmaintz.github.io/tech-atlas/)"},"id":"cs/internet","url":{"en":"https://cmaintz.github.io/tech-atlas/en/terms/cs/internet/","da":"https://cmaintz.github.io/tech-atlas/da/terms/cs/internet/"},"term":{"en":"Internet","da":"Internettet"},"aka":{"en":["the net"],"da":["nettet"]},"domain":["cs"],"cluster":"networking","layer":"network","status":"current","era":1983,"summary":{"en":"The worldwide network of networks that lets almost any connected device reach almost any other.","da":"Det verdensomspændende netværk af netværk, der lader næsten enhver tilsluttet enhed nå næsten enhver anden."},"body":{"formal":{"en":"A global system of separately owned networks joined by routers, which all follow TCP/IP so that data from one network can be passed on and delivered to an IP address in another.","da":"Et globalt system af selvstændigt ejede netværk, forbundet af routere, som alle følger TCP/IP, så data fra ét netværk kan sendes videre og leveres til en IP-adresse i et andet."},"plain":{"en":"Like the world's post offices agreeing on one way to write addresses, so a letter posted in Denmark can reach a house in Tokyo.","da":"Som hvis alverdens postvæsener blev enige om én måde at skrive adresser på, så et brev sendt i Danmark kan nå et hus i Tokyo."},"inPractice":{"en":"A bakery with three shops runs its card terminals, web shop and email over a single internet connection; when the line goes down one morning, the shops can take only cash.","da":"Et bageri med tre butikker kører betalingsterminaler, webshop og e-mail over én internetforbindelse; da forbindelsen falder ud en morgen, kan butikkerne kun tage imod kontanter."},"whyItMatters":{"en":"A connection to the internet makes an organisation reachable by anyone in the world, which is why so many controls guard the point where its own network meets it.","da":"En forbindelse til internettet betyder, at alle i hele verden kan forsøge at nå organisationen, og derfor samles så mange kontroller dér, hvor dens eget netværk møder det."}},"deepDive":{"en":"The internet grew out of ARPANET, which carried its first messages in 1969 using the Network Control Program. On 1 January 1983 ARPANET switched to TCP/IP in a coordinated \"flag day\", which is why 1983 is usually given as the internet's birth year. Academic backbones such as NSFNET followed, and the commercial internet took over after NSFNET's backbone was retired in 1995. The World Wide Web, created by Tim Berners-Lee at CERN around 1989-1991, is an application running on the internet, not a synonym for it; email, DNS, VPNs and industrial telemetry use the same infrastructure.\n\nTechnically the internet is a mesh of autonomous systems (AS): networks under one administrative routing policy, each identified by an AS number. They exchange reachability information with BGP-4 (RFC 4271), and routing between them follows business policy rather than shortest paths: customers pay providers for transit, while networks of similar size often exchange traffic settlement-free through peering, frequently at internet exchange points. Unique identifiers are coordinated hierarchically: IANA allocates address blocks and AS numbers to five Regional Internet Registries (AFRINIC, APNIC, ARIN, LACNIC and RIPE NCC, which serves Europe including Denmark, the Middle East and parts of Central Asia), and the DNS root zone anchors the name space.\n\nThe architecture rests on a few design choices. IP offers only best-effort datagram delivery, with no guarantees of delivery, order or timing; reliability is added in the end hosts, following the end-to-end argument of Saltzer, Reed and Clark (1984). IP is the \"narrow waist\" of an hourglass: many link technologies below, many applications above. The core routers keep no per-connection state, which made the network scalable and resilient but left security out of the original design.\n\nSeveral persistent weaknesses follow from that. IP does not authenticate source addresses, enabling spoofing and reflection DDoS attacks unless networks apply ingress filtering (BCP 38). BGP accepts route announcements largely on trust, so misconfigurations and hijacks can redirect traffic for whole prefixes, as when Pakistan Telecom's announcement took YouTube offline globally in 2008; Resource Public Key Infrastructure with route origin validation (RFC 6811) is the main countermeasure. For an organisation, being connected means being continuously scanned: search engines such as Shodan and Censys index exposed services, and newly exposed services are typically probed within hours. External attack surface management, redundant upstream connections and DDoS protection are therefore standard controls at the point where the internal network meets the internet.","da":"Internettet voksede ud af ARPANET, som sendte sine første beskeder i 1969 med Network Control Program. Den 1. januar 1983 skiftede ARPANET til TCP/IP på en koordineret \"flag day\", og derfor angives 1983 normalt som internettets fødselsår. Akademiske backbone-net som NSFNET fulgte, og det kommercielle internet tog over, efter at NSFNET's backbone blev nedlagt i 1995. World Wide Web, som Tim Berners-Lee skabte på CERN omkring 1989-1991, er en applikation, der kører på internettet, ikke et synonym for det; e-mail, DNS, VPN og industriel telemetri bruger den samme infrastruktur.\n\nTeknisk er internettet et net af autonome systemer (AS): netværk under én administrativ routingpolitik, hver identificeret af et AS-nummer. De udveksler oplysninger om, hvad der kan nås, med BGP-4 (RFC 4271), og routing mellem dem følger forretningsmæssige hensyn snarere end korteste vej: Kunder betaler udbydere for transit, mens netværk af nogenlunde samme størrelse ofte udveksler trafik gratis via peering, typisk på internetudvekslingspunkter (IXP'er). Unikke identifikatorer koordineres hierarkisk: IANA tildeler adresseblokke og AS-numre til fem regionale internetregistre (AFRINIC, APNIC, ARIN, LACNIC og RIPE NCC, som dækker Europa inklusive Danmark, Mellemøsten og dele af Centralasien), og DNS-rodzonen er ankeret for navnerummet.\n\nArkitekturen hviler på få designvalg. IP tilbyder kun best-effort-levering af datagrammer uden garanti for levering, rækkefølge eller timing; pålidelighed lægges ud i endepunkterne efter end-to-end-argumentet fra Saltzer, Reed og Clark (1984). IP er den \"smalle talje\" i et timeglas: mange linkteknologier nedenunder, mange applikationer ovenover. Routerne i kernen holder ingen tilstand pr. forbindelse, hvilket gjorde nettet skalerbart og robust, men sikkerhed var ikke en del af det oprindelige design.\n\nDet giver nogle vedvarende svagheder. IP autentificerer ikke afsenderadresser, hvilket muliggør spoofing og reflektionsbaserede DDoS-angreb, medmindre netværkene anvender ingress-filtrering (BCP 38). BGP accepterer i vid udstrækning ruteannonceringer på tillid, så fejlkonfigurationer og kapringer kan omdirigere trafik for hele præfikser, som da Pakistan Telecoms annoncering tog YouTube ned globalt i 2008; Resource Public Key Infrastructure med validering af ruteoprindelse (RFC 6811) er den vigtigste modforanstaltning. For en organisation betyder en internetforbindelse, at den konstant bliver scannet: Søgemaskiner som Shodan og Censys indekserer eksponerede tjenester, og nyeksponerede tjenester bliver typisk afprøvet inden for timer. Styring af den eksterne angrebsflade, redundante forbindelser til internetudbydere og DDoS-beskyttelse er derfor standardkontroller dér, hvor det interne netværk møder internettet."},"edges":[{"type":"requires","to":"cs/tcp-ip","confidence":"high","strength":"normal"},{"type":"requires","to":"cs/ip-address","confidence":"high","strength":"normal"},{"type":"requires","to":"cs/router","confidence":"high","strength":"normal"},{"type":"kind-of","to":"cs/network","confidence":"high","strength":"normal"}],"depth":4,"sources":[{"title":"Kurose & Ross, Computer Networking: A Top-Down Approach","tier":"textbook"},{"title":"Tanenbaum, Computer Networks","tier":"textbook"}],"draft":true}