Appendix A Infrastructure for Electronic Commerce

Regardless of their basic purpose, virtually all e-commerce sites rest on the same network structures,communication protocols, and Web standards. This infrastructure has been under development for over 30years. This appendix briefly reviews the structures, protocols and standards underlying the millions of sitesused to sell to, service, and chat with both customers and business partners. It also looks at the infrastructureof some newer network applications, including streaming media and peer-to-peer (P2P)....
Nội dung trích xuất từ tài liệu:
Appendix A Infrastructure for Electronic CommerceAppendix AInfrastructure for Electronic CommerceRegardless of their basic purpose, virtually all e-commerce sites rest on the same network structures,communication protocols, and Web standards. This infrastructure has been under development for over 30years. This appendix briefly reviews the structures, protocols and standards underlying the millions of sitesused to sell to, service, and chat with both customers and business partners. It also looks at the infrastructureof some newer network applications, including streaming media and peer-to-peer (P2P).A.1 NETWORK OF NETWORKSWhile many of us use the Web and the Internet on a daily basis, few of us have a clear understanding of itsbasic operation. From a physical standpoint, the Internet is a network of 1000s of interconnected networks.Included among the interconnected networks are: (1) the interconnected backbones which have internationalreach; (2) a multitude of access/delivery sub-networks; and (3) thousands of private and institutionalnetworks connecting various organizational servers and containing much of the information of interest. Thebackbones are run by the network service providers (NSPs) which include the major telecommunicationcompanies like MCI and Sprint. Each backbone handles hundreds of terabytes of information per month.The delivery sub-networks are provided by the local and regional Internet Service Providers (ISPs). TheISPs exchange data with the NSPs at the network access points (NAPs). Pacific Bell NAP (San Francisco)and Ameritech NAP (Chicago) are examples of these exchange points. When a user issues a request on the Internet from his or her computer, the request will likely traverse anISP network, move over one or more of the backbones, and across another ISP network to the computercontaining the information of interest. The response to the request will follow a similar sort of path. For anygiven request and associated response, there is no preset route. In fact the request and response are eachbroken into packets and the packets can follow different paths. The paths traversed by the packets aredetermined by special computers called routers. The routers have updateable maps of the networks on theInternet that enable them to determine the paths for the packets. Cisco (www.cisco.com) is one of thepremier providers of high speed routers. One factor that distinguishes the various networks and sub-networks is their speed or bandwidth. Thebandwidth of digital networks and communication devices are rated in bits per second. Most consumersconnect to the Internet over the telephone through digital modems whose speeds range from 28.8 kbps to 56kbps (kilobits per second). In some residential areas or at work, users have access to higher-speedconnections. The number of homes, for example, with digital subscriber line (DSL) connections or cableconnections is rapidly increasing. DSL connections run at 1 to 1.5 mbps (megabits per second), while cableconnections offer speeds of up to 10 mbps. A megabit equals 1 million bits. Many businesses are connectedto their ISPs via a T-1 digital circuit. Students at many universities enjoy this sort of connection (orsomething faster). The speed of a T-1 line is 1.544 mbps. The speeds of various Internet connections aresummarized in Table A.1. . You’ve probably heard the old adage that a chain is only as strong as its weakest link. In the Internetthe weakest link is the “last mile” or the connection between a residence or business and an ISP. At 56 kbps,downloading anything but a standard Web page is a tortuous exercise. A standard Web page with text andgraphics is around 400 kilobits. With a 56K modem, it takes about 7 seconds to retrieve the page. A cablemodem takes about .04 seconds. The percentage of residences in the world with broadband connections (e.g.cable or DSL) is very low. In the U.S. the figure is about 4% of the residences. Obviously, this is a majorimpediment for e-commerce sites utilizing more advanced multi-media or streaming audio and videotechnologies which require cable modem or T-1 speeds.Appendix A Infrastructure for Electronic Commerce 1TABLE A.1 Bandwidth SpecificationsTechnology Speed Description ApplicationDigital Model 56 Kbps Data over public Dialup telephone networksADSL – Asynchronous 1.5 to 8.2 Mbps Data over public Residential andDigital Subscriber line telephone network commercial hookupsCable Modem 1 to 10 Mbps Data over the cable Residential hookups networkT-1 1.544 Mbps Dedicated digital circuit Company backbone to ISPT-3 44.736 Mbps Dedicated digital circuit ISP to Internet infrastructure. Smaller links in Internet infrastructureOC-3 155.52 Mbps Optical fiber carrier Large company backbone to Internet backboneOC-12 622.08 Mbps Optical fiber carrier Intern ...