Converging Networks

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This Handbook presents the ITU-T Recommendations on next generation networks in the context of the ongoing convergence of the telecommunications and media industries.



Overview of IP network technology

The Internet is often described as a "network of networks" arising from the interconnection of millions of commercial, academic, government and private networks that use the Internet Protocol (IP) to provide connectivity. Organizationally, the Internet has a "tiered" structure with Tier 1 networks at the core, to which Tier 2 networks are connected, to which in turn Tier 3 networks are connected. Tier 1 networks, of which there are about a dozen in the world, are interconnected with their peers on a settlement-free basis as they can provide large volumes of traffic. Tier 2 operators peer with some operators but pay Tier 1 operators to access some parts of the Internet and Tier 3 operators rely solely on transit capabilities provided by other operators. Internet eXchange Points (IXPs) allow direct communication between Internet service providers and reduce transit costs. There are about 400 IXPs in 87 countries [ITU Tel Reform].


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