Editing Internet exchange point

{{Short description|Internet infrastructure through which ISPs exchange traffic}}
{{Use American English|date=January 2019}}
{{Use dmy dates|date=April 2015}}
{{Internet history timeline}}

'''Internet exchange points''' ('''IXes''' or '''IXPs''') are common grounds of [[Internet Protocol|IP]] networking, allowing participant [[Internet service provider|Internet service providers (ISPs)]] to exchange data destined for their respective networks.<ref>{{cite web|title=The Art of Peering - The IX Playbook|url=http://www.drpeering.net/white-papers/Art-Of-Peering-The-IX-Playbook.html|access-date=18 April 2015|archive-date=20 December 2017|archive-url=https://web.archive.org/web/20171220190247/http://www.drpeering.net/white-papers/Art-Of-Peering-The-IX-Playbook.html|url-status=live}}</ref>  IXPs are generally located at places with preexisting connections to multiple distinct networks, ''i.e.'', [[Datacenter|datacenters]], and operate physical infrastructure ([[Ethernet switch|switches]]) to connect their participants.  Organizationally, most IXPs are each independent not-for-profit associations of their constituent participating networks (that is, the set of ISPs that participate in that IXP). The primary alternative to IXPs is [[private peering]], where ISPs directly connect their networks.

IXPs reduce the portion of an ISP's traffic that must be delivered via their [[upstream (networking)|upstream]] [[Internet transit|transit]] providers, thereby reducing the [[average per-bit delivery cost]] of their service.  Furthermore, the increased number of paths available through the IXP improves [[Least-cost routing|routing efficiency]] (by allowing routers to select shorter paths) and [[fault-tolerance]]. IXPs exhibit the characteristics of the [[network effect]].<ref>{{cite web|title=Internet Service Providers and Peering v3.0|url=http://www.drpeering.net/white-papers/Internet-Service-Providers-And-Peering.html|access-date=18 April 2015|archive-date=20 April 2015|archive-url=https://web.archive.org/web/20150420130051/http://drpeering.net/white-papers/Internet-Service-Providers-And-Peering.html|url-status=live}}</ref><ref>https://www.datacenterdynamics.com/en/news/awasr-ams-ix-and-alliance-networks-launch-internet-exchange-in-oman/</ref>

==History==
{{globalize|section|United States|date=March 2025}}
[[File:NewNSFNETArchitecture.jpg|thumb|upright=2.0|[[NSFNet]] Internet architecture, {{circa|1995}}]]

Internet exchange points began as '''Network Access Points''' or '''NAPs''', a key component of [[Al Gore]]'s [[National Information Infrastructure]] (NII) plan, which defined the transition from the US Government-paid-for [[National Science Foundation Network|NSFNET]] era (when Internet access was government sponsored and commercial traffic was prohibited) to the commercial Internet of today. The four Network Access Points (NAPs) were defined as transitional data communications facilities at which Network Service Providers (NSPs) would exchange traffic, in replacement of the publicly financed [[NSFNET]] Internet backbone.<ref>[http://w2.eff.org/Infrastructure/Govt_docs/nsf_nren.rfp NSF Solicitation 93-52] {{webarchive|url=https://web.archive.org/web/20160305030153/https://w2.eff.org/Infrastructure/Govt_docs/nsf_nren.rfp |date=2016-03-05 }} - Network Access Point Manager, Routing Arbiter, Regional Network Providers, and Very High Speed Backbone Network Services Provider for NSFNET and the NREN(SM) Program, May 6, 1993</ref><ref name=prescriptive-policy-guide>{{cite web |last=Woodcock |first=Bill |author-link=Bill Woodcock |title=Prescriptive Policy Guide for Developing Nations Wishing to Encourage the Formation of a Domestic Internet Industry |publisher=[[Packet Clearing House]] |date=March 2001 |url=https://www.pch.net/resources/papers/policy-guide/policy-guide.html |access-date=10 August 2021 |archive-date=3 June 2021 |archive-url=https://web.archive.org/web/20210603065525/https://www.pch.net/resources/Papers/policy-guide/policy-guide.html |url-status=live }}</ref>  The [[National Science Foundation]] let contracts supporting the four NAPs, one to [[Metropolitan Fiber Systems|MFS Datanet]] for the preexisting [[MAE-East]] in Washington, D.C., and three others to [[Sprint Nextel|Sprint]], [[Ameritech]], and [[Pacific Bell]], for new facilities of various designs and technologies, in New York (actually [[Pennsauken, New Jersey]]), Chicago, and California, respectively.<ref>[http://www.merit.edu/mail.archives/mjts/1994-03/msg00001.html E-mail regarding Network Access Points from Steve Wolff (NSF) to the com-priv list] {{webarchive|url=https://web.archive.org/web/20131029195813/http://www.merit.edu/mail.archives/mjts/1994-03/msg00001.html |date=2013-10-29 }}, sent 13:51 EST 2 March 1994</ref>  As a transitional strategy, they were effective, providing a bridge from the Internet's beginnings as a government-funded academic experiment, to the modern Internet of many private-sector competitors collaborating to form a network-of-networks, transporting Internet bandwidth from its points-of-production at Internet exchange points to its sites-of-consumption at users' locations.

This transition was particularly timely, coming hard on the heels of the [[National_Science_Foundation_Network#Controversy|ANS CO+RE controversy]],<ref>{{Cite web |url=http://www.cookreport.com/ |title=The Cook Report on the Internet |access-date=10 August 2021 |archive-date=5 August 2021 |archive-url=https://web.archive.org/web/20210805001912/http://cookreport.com/ |url-status=live }}</ref><ref>[http://www.cookreport.com/index.php?option=com_content&view=article&id=216:310&catid=53:1995&Itemid=63 "A Critical Look at the University of Michigan's Role in the 1987 Merit Agreement"] {{Webarchive|url=https://web.archive.org/web/20210810194235/http://www.cookreport.com/index.php?option=com_content&view=article&id=216:310&catid=53:1995&Itemid=63 |date=10 August 2021 }}, Chetly Zarko in ''The Cook Report on the Internet'', January 1995, pp. 9–17</ref> which had disturbed the nascent industry, led to congressional hearings,<ref>[http://www.eric.ed.gov/ERICWebPortal/search/recordDetails.jsp?ERICExtSearch_SearchValue_0=ED350986&searchtype=keyword&ERICExtSearch_SearchType_0=no&_pageLabel=RecordDetails&accno=ED350986&_nfls=false Management of NSFNET] {{Webarchive|url=https://web.archive.org/web/20130728150959/http://www.eric.ed.gov/ERICWebPortal/search/recordDetails.jsp?ERICExtSearch_SearchValue_0=ED350986&searchtype=keyword&ERICExtSearch_SearchType_0=no&_pageLabel=RecordDetails&accno=ED350986&_nfls=false |date=28 July 2013 }}, a transcript of the March 12, 1992, hearing before the Subcommittee on Science of the [[Committee on Science, Space, and Technology]], U.S. House of Representatives, [[One Hundred Second Congress]], Second Session, Hon. [[Rick Boucher]], subcommittee chairman, presiding</ref> resulted in a law allowing NSF to promote and use networks that carry commercial traffic,<ref>[http://thomas.loc.gov/cgi-bin/bdquery/z?d102:S.1146: Scientific and Advanced-Technology Act of 1992] {{Webarchive|url=https://web.archive.org/web/20160705025503/http://thomas.loc.gov/cgi-bin/bdquery/z?d102:S.1146: |date=5 July 2016 }}, Public Law No: 102-476, 43 U.S.C. 1862(g)</ref> prompted a review of the administration of NSFNET by the NSF's Inspector General (no serious problems were found),<ref>[https://www.nsf.gov/pubs/stis1993/oig9301/oig9301.txt Review of NSFNET] {{Webarchive|url=https://web.archive.org/web/20170706035156/https://www.nsf.gov/pubs/stis1993/oig9301/oig9301.txt |date=6 July 2017 }}, Office of the Inspector General, National Science Foundation, 23 March 1993</ref> and caused commercial operators to realize that they needed to be able to communicate with each other independent of third parties or at neutral exchange points.

Although the three telco-operated NAPs faded into obscurity relatively quickly after the expiration of the federal subsidies, [[MAE-East]], thrived for fifteen more years, and its west-coast counterpart [[MAE-West]] continued for more than twenty years.<ref>{{cite web |last1=Garfinkel |first1=Simson |title=Where Streams Converge |url=https://simson.net/clips/1996/96.HW.MAE_West.pdf |date=11 September 1996 |access-date=11 November 2021 |archive-date=11 November 2021 |archive-url=https://web.archive.org/web/20211111123341/https://simson.net/clips/1996/96.HW.MAE_West.pdf |url-status=live }}</ref>

Today, the phrase "Network Access Point" is of historical interest only, since the four transitional NAPs disappeared long ago, replaced by hundreds of modern Internet exchange points, though in Spanish-speaking [[Latin America]], the phrase lives on to a small degree, among those who conflate the NAPs with IXPs.{{citation needed|date=August 2023}}

==Function==
[[File:TelehouseDocklands.jpg|thumb|left|Initial location of the [[London Internet Exchange]] (LINX): [[Telehouse Europe|Telehouse Docklands]]]]

The primary purpose of an IXP is to allow networks to interconnect directly, via the exchange, rather than going through one or more third-party networks. The primary advantages of direct interconnection are cost, [[Network latency |latency]], and [[Bandwidth (computing)|bandwidth]].<ref name=prescriptive-policy-guide />

Traffic passing through an exchange is typically not billed by any party, whereas traffic to an ISP's [[upstream (networking)|upstream]] provider is.<ref>{{cite book |author1=Ryan, Patrick S. |author2=Gerson, Jason |title=A Primer on Internet Exchange Points for Policymakers and Non-Engineers |date=11 August 2012 |publisher=Social Science Research Network (SSRN) |ssrn=2128103}}</ref>  The direct interconnection, often located in the same city as both networks, avoids the need for data to travel to other cities—and potentially on other continents—to get from one network to another, thus reducing latency.<ref name=oecd-market-developments>{{cite journal |last1=Woodcock |first1=Bill |author-link=Bill Woodcock |last2=Weller |first2=Dennis |title=Internet Traffic Exchange: Market Developments and Policy Challenges |publisher=[[OECD]] |journal=Digital Economy Papers |series=OECD Digital Economy Papers |date=January 29, 2013 |doi=10.1787/5k918gpt130q-en |url=http://www.oecd-ilibrary.org/science-and-technology/internet-traffic-exchange_5k918gpt130q-en |access-date=10 August 2021 |archive-date=10 August 2021 |archive-url=https://web.archive.org/web/20210810194458/https://www.oecd-ilibrary.org/science-and-technology/internet-traffic-exchange_5k918gpt130q-en |url-status=live |doi-access=free }}</ref>

The third advantage, speed, is most noticeable in areas that have poorly developed long-distance connections. ISPs in regions with poor connections might have to pay between 10 or 100 times more for data transport than ISPs in North America, Europe, or Japan. Therefore, these ISPs typically have slower, more limited connections to the rest of the Internet. However, a connection to a local IXP may allow them to transfer data without limit, and without cost, vastly improving the bandwidth between customers of such adjacent ISPs.<ref name=oecd-market-developments />

Internet Exchange Points (IXPs) are public locations where several networks are connected to each other.<ref>{{cite book | url=https://books.google.com/books?id=IM-Y2W0RIF0C&dq=tier+1+peering&pg=PA293 | title=Network Routing: Algorithms, Protocols, and Architectures | date=19 July 2010 | publisher=Elsevier | isbn=978-0-08-047497-7 }}</ref><ref>{{cite book | url=https://books.google.com/books?id=IM-Y2W0RIF0C&dq=internet+exchange+point+tier+1&pg=PA291 | isbn=978-0-08-047497-7 | title=Network Routing: Algorithms, Protocols, and Architectures | date=19 July 2010 | publisher=Elsevier }}</ref> Public peering is done at IXPs, while private peering can be done with direct links between networks.<ref>{{cite book | url=https://books.google.com/books?id=vXZODwAAQBAJ&dq=tier+1+peering&pg=PA156 | title=Information Network Engineering | date=20 July 2015 | publisher=株式会社 オーム社 | isbn=978-4-274-99991-8 }}</ref><ref name="Springer">{{cite book | url=https://books.google.com/books?id=MgDQDwAAQBAJ&dq=tier+1+peering&pg=PA88 | title=Internet Computing: Principles of Distributed Systems and Emerging Internet-Based Technologies | isbn=978-3-030-34957-8 | last1=Sunyaev | first1=Ali | date=12 February 2020 | publisher=Springer }}</ref>

==Operations==
[[File:DE-CIX GERMANY - Switch Rack (6218137120).jpg|thumb|A [[19-inch rack]] used for [[Network switch|switch]]es at the [[Deutscher Commercial Internet Exchange|DE-CIX]] in [[Frankfurt am Main|Frankfurt]], Germany]]

===Technical operations ===
A typical IXP consists of one or more [[network switch]]es, to which each of the participating ISPs connect. Prior to the existence of switches, IXPs typically employed [[fiber-optic inter-repeater link]] (FOIRL) hubs or [[Fiber Distributed Data Interface]] (FDDI) rings, migrating to [[Ethernet]] and FDDI switches as those became available in 1993 and 1994.

[[Asynchronous Transfer Mode]] (ATM) switches were briefly used at a few IXPs in the late 1990s, accounting for approximately 4% of the market at their peak, and there was an attempt by [[Stockholm]]-based IXP [[NetNod]] to use [[SRP/DPT]], but [[Ethernet]] has prevailed, accounting for more than 95% of all existing Internet exchange switch fabrics.  All Ethernet port speeds are to be found at modern IXPs, ranging from 10 [[Megabit|Mb]]/second ports in use in small developing-country IXPs, to ganged 10 [[Gigabit|Gb]]/second ports in major centers like Seoul, New York, London, Frankfurt, Amsterdam, and Palo Alto. Ports with 100 Gb/second are available, for example, at the AMS-IX in Amsterdam and at the DE-CIX in Frankfurt.{{Citation needed|date=August 2021}}

[[File:AMS-IX optical patch panel.jpg|thumb|An [[optical fiber]] [[patch panel]] at the [[Amsterdam Internet Exchange]]]]

=== Business operations ===
The principal business and governance models for IXPs include:<ref name=oecd-market-developments />
* [[Nonprofit organization|Not-for-profit]] [[Trade association|association]] (usually of the participating [[Internet service provider|ISPs]])
* [[Network-neutral data center|Operator-neutral]] for-profit company (usually the operator of a [[Data center|datacenter]] hosting the IXP)
* [[University]]
* [[Government agency]] (often the [[List of ministries of communications|communications ministry]] or [[List of telecommunications regulatory bodies|regulator]], at national scale, or [[Municipality|municipal government]], at local scale)
* [[Voluntary_association#Legal_status|Unincorporated informal association]] of networks (defined by an open-ended multi-party contract, without independent legal existence)

The technical and business logistics of traffic exchange between ISPs is governed by bilateral or multilateral [[peering]] agreements. Under such agreements, traffic is exchanged without compensation.<ref name="pch-peering-survey-2016">{{cite web |last1=Woodcock |first1=Bill |last2=Frigino |first2=Marco |title=2016 Survey of Internet Carrier Interconnection Agreements |url=https://www.pch.net/resources/Papers/peering-survey/PCH-Peering-Survey-2016/PCH-Peering-Survey-2016.pdf |publisher=Packet Clearing House |date=21 November 2016 |quote=Of the agreements we analyzed, 1,935,111 (99.98%) had symmetric terms, in which each party gave and received the same conditions as the other. Only 403 (0.02%) had asymmetric terms, in which the parties gave and received conditions with specifically defined differences, and these exceptions were down from 0.27% in 2011. Typical examples of asymmetric agreements are ones in which one of the parties compensates the other for routes that it would not otherwise receive (sometimes called 'paid peering' or 'on-net routes'), or in which one party is required to meet terms or requirements imposed by the other ('minimum peering requirements'), often concerning volume of traffic or number or geographic distribution of interconnection locations. In the prevailing symmetric relationship, the parties to the agreement simply exchange customer routes with each other, without settlements or other requirements. |access-date=11 November 2021 |archive-date=7 July 2021 |archive-url=https://web.archive.org/web/20210707084312/https://www.pch.net/resources/Papers/peering-survey/PCH-Peering-Survey-2016/PCH-Peering-Survey-2016.pdf |url-status=live }}</ref> When an IXP incurs operating costs, they are typically shared among all of its participants.

At the more expensive exchanges, participants pay a monthly or annual fee, usually determined by the speed of the port or ports which they are using. Fees based on the volume of traffic are less common because they provide a counterincentive to the growth of the exchange. Some exchanges charge a setup fee to offset the costs of the switch port and any media adaptors ([[gigabit interface converter]]s, [[small form-factor pluggable transceiver]]s, [[XFP transceiver]]s, [[XENPAK]]s, etc.) that the new participant requires.

==Traffic exchange ==
[[File:IXP Topology L1-L2.svg|thumb|Diagram of the Layer 1 (physical) and Layer 2 (Data Link) topology of an Internet exchange point (IXP)]]
[[File:IXP Topology L3.svg|thumb|Diagram of the Layer 3 (network) topology of an Internet exchange point (IXP)]]

Internet traffic exchange between two participants on an IXP is facilitated by [[Border Gateway Protocol]] (BGP) routing configurations between them. They choose to announce routes via the peering relationship&nbsp;– either routes to their own addresses or routes to addresses of other ISPs that they connect to, possibly via other mechanisms. The other party to the peering can then apply [[route filtering]], where it chooses to accept those routes, and route traffic accordingly, or to ignore those routes, and use other routes to reach those addresses.

In many cases, an ISP will have both a direct link to another ISP and accept a route (normally ignored) to the other ISP through the IXP; if the direct link fails, traffic will then start flowing over the IXP. In this way, the IXP acts as a backup link.

When these conditions are met, and a contractual structure exists to create a market to purchase network services, the IXP is sometimes called a "transit exchange". The Vancouver Transit Exchange, for example, is described as a "shopping mall" of service providers at one central location, making it easy to switch providers, "as simple as getting a [[VLAN]] to a new provider".<ref>{{cite web |url=http://billstarnaud.blogspot.com/2009/06/how-r-networks-can-help-small-business.html |title=Transit Exchange helps Novus Entertainment Save on Internet Costs and Improve Performance |work=How R&E networks can help small business |author=BCnet |publisher=Bill St. Arnaud |date=4 June 2009 |access-date=2012-09-11 |archive-date=21 August 2014 |archive-url=https://web.archive.org/web/20140821233756/http://billstarnaud.blogspot.com/2009/06/how-r-networks-can-help-small-business.html |url-status=live }}</ref> The VTE is run by BCNET, a public entity.

Advocates of green broadband schemes and more competitive telecommunications services often advocate aggressive expansion of transit exchanges into every municipal area network so that competing service providers can place such equipment as [[video on demand]] hosts and [[PSTN]] switches to serve existing phone equipment, without being answerable to any monopoly incumbent.

Since the dissolution of the [[Internet backbone]] and transition to the IXP system in 1992, the measurement of Internet traffic exchanged at IXPs has been the primary source of data about Internet bandwidth production: how it grows over time and where it is produced.<ref name=oecd-market-developments /> Standardized measures of bandwidth production have been in place since 1996<ref name="standardized-format-1996">{{cite web |last1=Claffy |first1=Kimberly |last2=Siegel |first2=Dave |last3=Woodcock |first3=Bill |title=Standarized Format for Exchange Point Traffic Recording & Interchange |url=http://www.academ.com/nanog/may1996/trafficstatistics.html |publisher=North American Network Operators Group |date=30 May 1996 |access-date=27 October 2021 |archive-date=3 December 1998 |archive-url=https://web.archive.org/web/19981203120611/http://www.academ.com/nanog/may1996/trafficstatistics.html |url-status=live }}</ref> and have been refined over time.<ref name="ixp-documentation-2007">{{cite book|publisher=OECD |title=Good Practices in Internet Exchange Point Documentation and Measurement |date=26 April 2007 |url=https://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=DSTI%2FICCP%2FCISP%282007%299&docLanguage=En |access-date=27 October 2021 |archive-date=19 January 2022 |archive-url=https://web.archive.org/web/20220119085322/https://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=DSTI%2FICCP%2FCISP%282007%299&docLanguage=En |url-status=live }}</ref>

==See also==
* Historical IXPs
** [[MAE-East]] and [[MAE-West]]
** [[Commercial Internet eXchange]] (CIX)
** [[Federal Internet Exchange]] (FIX) 
* Associations of Internet exchange point operators:
** [[Euro-IX]], the European Internet Exchange Association<ref>{{cite web |title=Euro-IX Website |publisher=European Internet Exchange |url=https://www.euro-ix.net |archive-url=https://web.archive.org/web/20150413121337/https://www.euro-ix.net/euro-ix | archive-date=13 April 2015}}</ref>
** [[APIX]], the Asia Pacific Internet Exchange Association
** [[LAC-IX]], the Latin America & Caribbean Internet Exchange Association
** [[African IXP Association|Af-IX]], the African IXP Association
* [[Route server]]
* [[Internet service provider]]
* [[Data center]]
* [[Packet Clearing House]]
* [[List of Internet exchange points]]
* [[Meet-me room]]
*[[Peering]]

== References ==
{{Reflist}}

==External links==
* [http://www.euro-ix.net European Internet Exchange Association]
* [http://www.pch.net/ixpdir Internet Exchange Directory] maintained by [[Packet Clearing House]]
* [http://www.datacentermap.com/ixps.html Internet Exchange Points] from Data Center Map
* [https://www.zotero.org/groups/4944209/ixp_history_collection_-_information_directory/ IXP History Collection]
* [http://www.peeringdb.com/ PeeringDB]
* [http://lookinglass.org/wix.php Lookin'Glass.Org] BGP Looking Glass services at IX's.

[[Category:Internet exchange points]]
[[Category:Routing]]