Traffic Exchange Across An Internet Exchange Point
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 — 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." The VTE is run by BCNET, a public entity.
Advocates of green broadband schemes and more competitive telecom 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.
Further information: PeeringRead more about this topic: Internet Exchange Point
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