Editing Internet exchange point (section)

==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>