Eno ugh histo rylets see ho w it all wo rks if yo u

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Unformatted text preview: t grants. Figure 1 2. 1 The Int ernet is a net work of net works , and t hes e net works are connect ed t oget her. In t he diagram above, t he “s t at e. edu” camp us net work is connect ed t o ot her net works of t he Int ernet via t wo ISPs : Cogent and Verizon. Eno ugh histo ry—let’s see ho w it all wo rks! If yo u want to co mmunicate with ano ther co mputer o n the Internet then yo ur co mputer needs to kno w the answer to three questio ns: What are yo u lo o king f o r? Where is it? And ho w do we get there? The co mputers and so f tware that make up Internet inf rastructure can help pro vide the answers. Let’s lo o k at ho w it all co mes to gether. The URL: “What Are You Looking For?” When yo u type an address into a Web bro wser (so metimes called a URL f o r unifo rm reso urce lo cato r), yo u’re telling yo ur bro wser what yo u’re lo o king f o r. Figure 12.2 "Anato my o f a Web Address" describes ho w to read a typical URL. Figure 1 2. 2 Anat omy of a Web Addres s The URL dis p layed really s ays , “Us e t he Web (ht t p ://) t o find a hos t s erver named ‘ www’ in t he ‘ nyt imes . com’ net work, look in t he ‘ t ech’ direct ory, and acces s t he ‘ index . ht ml’ file. ” The http:/ / yo u see at the start o f mo st Web addresses stands f o r h ypert ext t ransf er prot ocol. A prot ocol is a set o f rules f o r co mmunicatio n—so rt o f like grammar and vo cabulary in a language like English. The http pro to co l def ines ho w Web bro wser and Web servers co mmunicate and is designed to be independent f ro m the co mputer’s hardware and o perating system. It do esn’t matter if messages co me f ro m a P C, a Mac, a huge mainf rame, o r a po cket-sized smartpho ne; if a device speaks to ano ther using a co mmo n pro to co l, then it will be heard and understo o d. The Internet suppo rts lo ts o f dif f erent applicatio ns, and many o f these applicatio ns use their o wn applicatio n transf er pro to co l to co mmunicate with each o ther. Th...
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