Internet Performance for Dummies

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14 Internet Performance For Dummies, Dyn Special Edition These materials are © 2015 John Wiley & Sons, Inc. Any dissemination, distribution, or unauthorized use is strictly prohibited. interconnect with other service providers in order to provide access to all parts of the Internet for their customers. There are essentially two types of interconnections: ✓ Peering (or settlement‐free): Links between two service provider networks that are free. ✓ Transit: Links between two service provider networks (or other entities) that aren't free. An ISP's customer technically purchases transit from the ISP. Bilateral peering arrangements exist for the mutual benefit of the two cooperating networks in the relationship. However, disputes can — and do — sometimes arise. When this hap- pens, things get ugly (see the sidebar "Peering matters" later in this chapter). Often a dispute will arise when one party believes that an existing peering arrangement is providing greater benefit to the other party than the benefit that is being received. The aggrieved party may then attempt to convert the peering arrangement to a transit link, forcing the other party to pay for the interconnection. In extreme cases, the link between the two networks may be unilaterally disconnected (or depeered), effectively making large parts of the Internet inaccessible to millions of customers in the case of a Tier 1 ISP. When this happens, other preexisting peering arrange- ments in the depeered provider's network may provide indi- rect access to the portions of the Internet that are no longer accessible (as long as the other party doesn't disallow alter- nate routing), but possibly along a less efficient or otherwise less‐than‐optimal route. Not all network outages are due to "technical difficulties." Oftentimes, an outage (or performance degradation) is the result of a political or financial dispute between two service providers. It's important for you to have visibility of the cur- rent and historical performance data of not only your ISP, but also any upstream provider networks that your ISP relies on for Internet access.

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