Internet Performance for Dummies

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Chapter 2: Internet 101 13 These materials are © 2015 John Wiley & Sons, Inc. Any dissemination, distribution, or unauthorized use is strictly prohibited. • Verizon Enterprise Solutions (formerly UUNET) • XO Communications • Zayo Group (formerly AboveNet) ✓ Tier 2: An ISP that peers with some networks without fees, but still purchases IP transit or pays settlement fees to reach a large portion of the Internet. ✓ Tier 3: An ISP that always purchases IP transit or pays settlement fees to reach any portion of the Internet. A Tier 1 network is a global network that can reach the entire Internet over its own network backbone, or via the network backbones of other Tier 1 networks. A Tier 1 ISP has recip- rocal peering relationships with every other Tier 1 ISP that permit them to use each other's network backbones without paying any transit or settlement fees — on the surface. In real- ity, various payments are often exchanged between the vari- ous Tier 1 ISPs, but these payments aren't necessarily known to the public. If that definition of a Tier 1 network seems a little too straight- forward and succinct, it's because it is! In addition to global Tier 1 networks, there are regional Tier 1 networks. A regional Tier 1 network is the same as a global Tier 1 net- work in all respects, except that it is confined to a specific region, such as a geographic area within a country (for example, the U.S. Southwest), an entire country (for example, the United States), or an entire continent (for example, North America). To extend its network beyond its specific region, a regional Tier 1 network can establish peering arrangements with, or purchase transit from, a global Tier 1 network, in much the same manner as a Tier 2 network. ISP Peering and Transit Arrangements The Internet is a patchwork of interconnections among ser- vice provider networks. No single provider network com- prises the Internet in its entirety. Instead, service providers

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