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  3. How does E-mail travel on the Internet to reach someone far away? When Jennifer, Who lives in Pasadena, Calif. wants to send

How does E-mail travel on the Internet to reach someone far away? When Jennifer, Who lives in Pasadena, Calif. wants to send

admin2010-06-18  64
问题          How does E-mail travel on the Internet to reach someone far away?
   When Jennifer, Who lives in Pasadena, Calif. wants to send an E-mail message from her home computer to her mother in Washington, D. C., she uses a local Internet service provider (ISP) such as EarthLink Network Inc.  (ELNK). EarthLink gives Jennifer access to the Internet, much in the way that a ramp puts a driver on the national highway system.
   After Jennifer’s computer makes a local telephone call to EarthLink’s local bank of modems, Jennifer types in her E-mail message and hits "send." Based on Mom’s E-mail address, EarthLink will recognize that Mom is a customer of an ISP in Washington called Erols Internet Inc. (RCNC). EarthLink will then send the E-mail to an Internet backbone provider, such as GTE Corp. (GTE), to route it along its way
What is a backbone provider and why is it important on the Internet?
   Backbone providers are the Internet players that typically own and lease long-haul fiber-optic cables spanning a large region. They also own the communications gear that directs traffic over the Internet. There are only a handful of major backbone providers, including MCI, WorldCom, Sprint Corp. , GTE, and PSINet Inc. (PSIX).
   Backbone providers connect to each other to exchange data between their customers. They also pick up and deliver traffic for a fee from the 7,000 or so smaller ISPs, who give residential and small-business users access to the Internet. Backbone carriers are like the highway system over which most of the freight of the Internet travels to reach its destination. How did the current backbone providers come to be?
   When the Internet was still a government-run system, there was only a single Internet backbone: the NSFNET, operated by the National Science Foundation, which connected the regional government-funded Internet networks that were run by various research universities. When the government privatized the NSFNET in 1995, companies such as MCI, UUNET Technologies (now owned by Worldcom), BBN (now owned by GTE), and PSINet stepped into the breach by setting up commercial Internet backbone services. Now, instead of one NSFNET backbone, there are many of them that link together to provide the global connectivity, that is the  Internet.
How do Internet companies connect to each other?
   When the NSFNET was privatized, the government set up three locations in the U. S. where various Internet backbone companies could place their communications gear side by side and connect to each other. These so-called "public peering points" are in Chicago, Palo Alto, Calif., and Pennsauken, N.J.. Later, the government sanctioned two industry-run public peering points called Metropolitan Access Exchange East and West — MAE-East, in Vienna, Va., and MAE- West in San Jose, Calif..
   The problem was, as the Internet grew, the public points became overburdened and traffic slowed at these bottlenecks. So backbone providers started making arrangements with each other, called "private peering." These are direct, bilateral connections between two carriers in which no fees are charged.
Do the largest backbone providers charge each other?
   Backbone providers aren’t charging peers now, but there is a lot of discussion about whether they should. Most industry experts say the Internet needs to develop some payment scheme. After all, it is now a commercial, profit-making business, not a government freebie.
   But the industry has not figured out how to calculate who owes what to whom. Without an industry standard or government regulation, smaller companies fear that larger ones will set these charges in an arbitrary and discriminatory fashion.
America’s first backbone Internet Service provider was ______.
选项 A、EarthLink
B、MCI
C、GTE Corp
D、NSFNET
答案D
解析
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