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Internet exchange points (IXes or IXPs) are common grounds of IP networking, allowing participant Internet service providers (ISPs) to exchange data destined for their respective networks. IXPs are generally located at places with preexisting connections to multiple distinct networks, ''i.e.'', datacenters, and operate physical infrastructure (
switches In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
) 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 which participate at that IXP). The primary alternative to IXPs is
private peering In computer networking, peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the "down-stream" users of each network. Peering is settlement-free, also known as "bill-and ...
, where ISPs directly connect their networks to each other. IXPs reduce the portion of an ISP's traffic that must be delivered via their
upstream Upstream may refer to: * Upstream (bioprocess) * ''Upstream'' (film), a 1927 film by John Ford * Upstream (networking) * ''Upstream'' (newspaper), a newspaper covering the oil and gas industry * Upstream (petroleum industry) * Upstream (software ...
transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1979 film), a 1979 Israeli film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world * ''Transit'' (2006 film), a 2006 ...
providers, thereby reducing the
average per-bit delivery cost Average Per-Bit Delivery Cost, or APBDC, is the cost accounting method by which Internet Service Providers (ISPs) calculate their cost of goods sold. Concept Average Per-Bit Delivery Cost divides the cost of however many bits were actually mo ...
of their service. Furthermore, the increased number of paths available through the IXP improves routing efficiency (by allowing routers to select shorter paths) and
fault-tolerance Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...
. IXPs exhibit the characteristics of the
network effect In economics, a network effect (also called network externality or demand-side economies of scale) is the phenomenon by which the value or utility a user derives from a good or service depends on the number of users of compatible products. Net ...
.


History

Internet exchange points began as Network Access Points or NAPs, a key component of
Al Gore Albert Arnold Gore Jr. (born March 31, 1948) is an American politician, businessman, and environmentalist who served as the 45th vice president of the United States from 1993 to 2001 under President Bill Clinton. Gore was the Democratic Part ...
's
National Information Infrastructure The National Information Infrastructure (NII) was the product of the High Performance Computing Act of 1991. It was a telecommunications policy buzzword, which was popularized during the Clinton Administration under the leadership of Vice-President ...
(NII) plan, which defined the transition from the US Government-paid-for
NSFNET The National Science Foundation Network (NSFNET) was a program of coordinated, evolving projects sponsored by the National Science Foundation (NSF) from 1985 to 1995 to promote advanced research and education networking in the United States. The p ...
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 The National Science Foundation Network (NSFNET) was a program of coordinated, evolving projects sponsored by the National Science Foundation (NSF) from 1985 to 1995 to promote advanced research and education networking in the United States. The p ...
Internet backbone. The
National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National I ...
let contracts supporting the four NAPs, one to MFS Datanet for the preexisting
MAE-East The MAE (later, MAE-East) was the first Internet Exchange Point (IXP). It began in 1992 with four locations in Washington, D.C., quickly extended to Vienna, Reston, and Ashburn, Virginia; and then subsequently to New York and Miami. Its name sto ...
in Washington, D.C., and three others to Sprint,
Ameritech AT&T Teleholdings, Inc., formerly known as Ameritech Corporation (and before that American Information Technologies Corporation), is an American telecommunications company that arose out of the 1984 AT&T divestiture. Ameritech was one of the se ...
, and
Pacific Bell The Pacific Bell Telephone Company (Pacific Bell or Pac Bell) is a telephone company that provides telephone service in California. The company is owned by AT&T through AT&T Teleholdings, and, though separate, is now marketed as “AT&T”. The ...
, for new facilities of various designs and technologies, in New York (actually
Pennsauken, New Jersey Pennsauken Township is a township in Camden County in the U.S. state of New Jersey. It is a suburb of Philadelphia. As of the 2020 U.S. census, the township's population was 37,074, reflecting an increase of 1,189 (+3.3%) from the 35,885 count ...
), Chicago, and California, respectively. 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 ANS CO+RE controversy, which had disturbed the nascent industry, led to congressional hearings, resulted in a law allowing NSF to promote and use networks that carry commercial traffic, prompted a review of the administration of NSFNET by the NSF's Inspector General (no serious problems were found), 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 The MAE (later, MAE-East) was the first Internet Exchange Point (IXP). It began in 1992 with four locations in Washington, D.C., quickly extended to Vienna, Reston, and Ashburn, Virginia; and then subsequently to New York and Miami. Its name sto ...
, thrived for fifteen more years, and its west-coast counterpart
MAE-West MAE-West was an Internet exchange point located on the west coast of the United States in Silicon Valley, in the South San Francisco Bay Area in California. It was established in November, 1994. Its name officially stands for "Metropolitan Area Ex ...
continued for more than twenty years. 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 Latin America or * french: Amérique Latine, link=no * ht, Amerik Latin, link=no * pt, América Latina, link=no, name=a, sometimes referred to as LatAm is a large cultural region in the Americas where Romance languages — languages derived f ...
, the phrase lives on to a small degree, among those who conflate the NAPs with IXPs.


Function

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, latency, and
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
. Traffic passing through an exchange is typically not billed by any party, whereas traffic to an ISP's
upstream Upstream may refer to: * Upstream (bioprocess) * ''Upstream'' (film), a 1927 film by John Ford * Upstream (networking) * ''Upstream'' (newspaper), a newspaper covering the oil and gas industry * Upstream (petroleum industry) * Upstream (software ...
provider is. 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. 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.


Operations


Technical operations

A typical IXP consists of one or more
network switch A network switch (also called switching hub, bridging hub, and, by the IEEE, MAC bridge) is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device. A netw ...
es, to which each of the participating ISPs connect. Prior to the existence of switches, IXPs typically employed
fiber-optic inter-repeater link Classic Ethernet is a family of 10 Mbit/s Ethernet standards, which is the first generation of Ethernet standards. In 10BASE-X, the 10 represents its maximum throughput of 10 Mbit/s, BASE indicates its use of baseband transmission, and ...
(FOIRL) hubs or
Fiber Distributed Data Interface Fiber Distributed Data Interface (FDDI) is a standard for data transmission in a local area network. It uses optical fiber as its standard underlying physical medium, although it was also later specified to use copper cable, in which case it m ...
(FDDI) rings, migrating to
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
and FDDI switches as those became available in 1993 and 1994.
Asynchronous Transfer Mode Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by American National Standards Institute (ANSI) and ITU-T (formerly CCITT) for digital transmission of multiple types of traffic. ATM was developed to meet the needs of ...
(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 Stockholm () is the Capital city, capital and List of urban areas in Sweden by population, largest city of Sweden as well as the List of urban areas in the Nordic countries, largest urban area in Scandinavia. Approximately 980,000 people liv ...
-based IXP
NetNod Netnod AB (previously Netnod Internet Exchange i Sverige AB) is a private limited company based in Stockholm, Sweden, that operates Internet exchange points and manages one of the thirteen root name servers for the Domain Name System (DNS). It a ...
to use SRP/DPT, but
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
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 Mb/second ports in use in small developing-country IXPs, to ganged 10 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.


Business operations

The principle business and governance models for IXPs include: *
Not-for-profit A nonprofit organization (NPO) or non-profit organisation, also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, public or social benefit, in co ...
association Association may refer to: *Club (organization), an association of two or more people united by a common interest or goal *Trade association, an organization founded and funded by businesses that operate in a specific industry *Voluntary associatio ...
(usually of the participating
ISPs An Internet service provider (ISP) is an organization that provides services for accessing, using, or participating in the Internet. ISPs can be organized in various forms, such as commercial, community-owned, non-profit, or otherwise private ...
) * Operator-neutral for-profit company (usually the operator of a
datacenter A data center (American English) or data centre (British English)See spelling differences. is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommunic ...
hosting the IXP) *
University A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, t ...
*
Government agency A government or state agency, sometimes an appointed commission, is a permanent or semi-permanent organization in the machinery of government that is responsible for the oversight and administration of specific functions, such as an administrati ...
(often the communications ministry or regulator, at national scale, or municipal government, at local scale) * 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 In computer networking, peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the "down-stream" users of each network. Peering is settlement-free, also known as "bill-and ...
agreements. Under such agreements, traffic is exchanged without compensation. 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 A gigabit interface converter (GBIC) is a standard for transceivers, first defined in 1995 and commonly used with Gigabit Ethernet and Fibre Channel for some time. By offering a standard, hot swappable electrical interface, a single gigabit po ...
s,
small form-factor pluggable transceiver Small Form-factor Pluggable connected to a pair of fiber-optic cables Small Form-factor Pluggable (SFP) is a compact, hot-pluggable network interface module format used for both telecommunication and data communications applications. An SF ...
s,
XFP transceiver The XFP (10 gigabit small form-factor pluggable) is a standard for transceivers for high-speed computer network and telecommunication links that use optical fiber. It was defined by an industry group in 2002, along with its interface to other e ...
s,
XENPAK XENPAK is a multisource agreement (MSA), instigated by Agilent Technologies and Agere Systems, that defines a fiber-optic or wired transceiver module which conforms to the 10 Gigabit Ethernet (10GbE) standard of the Institute of Electrical and Elec ...
s, etc.) that the new participant requires.


Traffic exchange

Internet traffic exchange between two participants on an IXP is facilitated by
Border Gateway Protocol Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it makes ...
(BGP) routing configurations between them. They choose to announce routes via the peering relationship – 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 In the context of network routing, route filtering is the process by which certain routes are not considered for inclusion in the local route database, or not advertised to one's neighbours. Route filtering is particularly important for the Borde ...
, 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 A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer ( OSI layer 2).IEEE 802.1Q-2011, ''1.4 VLAN aims and benefits'' In this context, virtual, refers to a ph ...
to a new provider". 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 Video on demand (VOD) is a media distribution system that allows users to access videos without a traditional video playback device and the constraints of a typical static broadcasting schedule. In the 20th century, broadcasting in the form of o ...
hosts and
PSTN The public switched telephone network (PSTN) provides infrastructure and services for public telecommunication. The PSTN is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local teleph ...
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. Standardized measures of bandwidth production have been in place since 1996 and have been refined over time.


See also

* Historical IXPs **
MAE-East The MAE (later, MAE-East) was the first Internet Exchange Point (IXP). It began in 1992 with four locations in Washington, D.C., quickly extended to Vienna, Reston, and Ashburn, Virginia; and then subsequently to New York and Miami. Its name sto ...
and
MAE-West MAE-West was an Internet exchange point located on the west coast of the United States in Silicon Valley, in the South San Francisco Bay Area in California. It was established in November, 1994. Its name officially stands for "Metropolitan Area Ex ...
**
Commercial Internet eXchange The Commercial Internet eXchange (CIX) was an early interexchange point that allowed the free exchange of TCP/IP traffic, including commercial traffic, between ISPs. It was an important initial effort toward creating the commercial Internet that w ...
(CIX) **
Federal Internet Exchange Federal Internet Exchange (FIX) points were policy-based network peering points where U.S. federal agency networks, such as the National Science Foundation Network (NSFNET), NASA Science Network (NSN), Energy Sciences Network (ESnet), and MILNET ...
(FIX) * Associations of Internet exchange point operators: ** Euro-IX, the European Internet Exchange Association ** APIX, the Asia Pacific Internet Exchange Association **
LAC-IX LAC-IX is an association of Internet exchange points in Latin American and Caribbean. LAC-IX is also part of the global IX-F Internet eXchange Federation. See also *List of Internet exchange points This is a list of Internet exchange points ( IXP ...
, the Latin America & Caribbean Internet Exchange Association ** Af-IX, the African IXP Association *
Route server A route server is a computer server that was originally developed by the Routing Arbiter project, with funding from the National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States governme ...
*
Internet service provider An Internet service provider (ISP) is an organization that provides services for accessing, using, or participating in the Internet. ISPs can be organized in various forms, such as commercial, community-owned, non-profit, or otherwise private ...
* Data center *
Packet Clearing House Packet Clearing House (PCH) is the international nonprofit organization responsible for providing operational support and security to critical internet infrastructure, including Internet exchange points and the core of the domain name system. ...
*
List of Internet exchange points This is a list of Internet exchange points ( IXPs). There are several sources for IXP locations, including Packet Clearing House, who have maintained the earliest list of IXPs, with global coverage since 1994. Also, Telegeography, PeeringDB and t ...
*
Peering In computer networking, peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the "down-stream" users of each network. Peering is settlement-free, also known as "bill-and ...


References

{{Reflist


External links


European Internet Exchange Association

Internet Exchange Directory
maintained by
Packet Clearing House Packet Clearing House (PCH) is the international nonprofit organization responsible for providing operational support and security to critical internet infrastructure, including Internet exchange points and the core of the domain name system. ...

Internet Exchange Points
from Data Center Map
PeeringDB

Lookin'Glass.Org
BGP Looking Glass services at IX's. Internet exchange points Routing