What is Internet addressing? A way to locate people, computers, and Internet resources. It can be
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IP (Internet Protocol) addresses and domain names Electronic mail addresses
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U!s
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In general, Internet addressing is a systematic way to identi"y people, computers and Internet resources. #n the Internet, the term $address$ is used loosely. Address can mean many di""erent things "rom an electronic mail address to a U!. 1.IP Address
An IP address is a uni%ue number that identi"ies computers on the Internet& e'ery computer directly connected to the Internet has one. E'ery client, ser'er and networ de'ice must ha'e a uni%ue u ni%ue IP address "or each networ connection (networ inter"ace). IP addresses are conceptually similar to phone numbers, ecept they are used in !A*s (!ocal Area *etwor), WA*s (Wide Area *etwor), and the Internet Internet.. +ecause the numbers are not easy "or humans hu mans to remember, the omain *ame -ystem pro'ides a ser'ice analogous to an address boo looup called $domain name resolution$ or $name resolution$. -pecial *- ser'ers on the internet are dedicated to per"orming the translation "rom a domain name to an IP address and '.'. An IP address consists o" "our numbers separated by periods. Each number must be between and /00. An eample is1 /2.34./0.5/ 6he "ormat o" an IP address add ress is a 5/7bit numeric address written as "our numbers separated by periods. Each number can be 8ero to /00. 9or eample, 4.4: .4./2 could be an IP address. Within an isolated networ, you can assign IP addresses at random as long as each one is uni%ue. ;owe'er, connecting a pri'ate networ to the Internet Internet re%uires re%uires using registered IP addresses (called Internet addresses) to a'oid duplicates. 6he "our numbers in an IP address are used in di""erent ways to identi"y a particular networ and a host on that networ. 9our regional Internet registries 77 AI*, IPE *<<, !A<*I< and AP*I< 77 assign Internet addresses "rom "rom the "ollowing three classes. •
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Format . An IP address is made up o" "our bytes o" in"ormation (totaling 5/ bits) epressed as "our numbers between and /00 shown separated by periods. 9or eample, your computer=s IP address might be /53.4>.40.2, which is shown below in human7 readable decimal "orm and in the binary "orm used on the Internet.
Example IP Address
ecimal1 +inary1
/53 . 4> . 40 . 2 444444 44 444444 4
Each o" the "our numbers uses eight bits o" storage, and so can represent any o" the /0: numbers between 8ero (binary ) and /00 (binary 44444444). 6here"ore, there are more than 2 billion possible di""erent IP addresses in all1 (Internet Protocol address) 6he address o" a de'ice attached to an IP networ (6
Each de'ice in an IP networ is either assigned a permanent address (static IP) by the networ administrator or is assigned a temporary address (dynamic IP). epending on one=s Internet connection the IP address can be the same e'ery time one connects (called a static IP address), or di""erent e'ery time one con nects, (called a dynamic IP address). In order to use a dynamic IP address, there must eist a ser'er, which can pro'ide the address. IP addresses are usually gi'en out through a ser'er ser'ice called ;
IP addresses are written in $dotted decimal$ notation, which is "our sets o" numbers separated by periods& "or eample, /2.4>4.:2./. I" you new the IP address o" a Web site, you could enter the dotted decimal number into your browser instead o" the domain
name .6he traditional IP address uses a 5/7bit number that de"ines both the networ a nd the host computer. 6he networ class determines how many o" the 5/ bits are used "or the networ address, lea'ing the remaining bits "or use as the host number. 6he host number can be "urther di'ided between subnetwors and hosts
Maximum Number of Networks
Maximum Hosts per Network
1-126 127 16,777,214 128-191 16,383 65,534 192-223 2,097,151 254 127 reserved for loopback test
Number of Bits used in Network/Host ID ID 7/24 14/16 21/8
An IP address is "irst di'ided between networs and hosts. 6he host bits are "urther di'ided between subnets and hosts.
More detail 6he Internet Protocol (IP) nows each logical host inter"ace by a number, the IP address. #n any gi'en networ, this number must be uni%ue among all the host inter"aces that communicate through this networ. Users o" the Internet are sometimes gi'en a host name in addition to their numerical IP address by their Internet ser'ice pro'ider. 6he IP addresses o" users browsing the World Wide Web are used to enable communications with the ser'er o" the web site. Also, it is usually in the header o" email messages one sends. In "act, "or all programs that u tili8e the 6
Domain Name
Cost computers on the Internet ha'e a uni%ue domain name. -pecial computers, called domain name ser'ers, loo up the domain name and match it to the corresponding IP address so that data can be properly routed to its destination on the Internet. An eample domain name is1 healthyway.com omain names are easier "or most people to relate to than a numeric IP address. 2.Electronic Mail Address
An Internet electronic mail, or e7mail, address is used to identi"y a person (or persons) and a computer "or purposes o" echanging electronic mail messages. An eample Internet e7mail address is1 abc4/5Dcolumbia.edu Internet e7mail addresses are read "rom le"t to right1 •
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$abc4/5$ is the name o" the person recei'ing or sending the message& this is re"erred to as the username. $columbia$ is part o" the domain name o" the organi8ation. $edu$ is also part o" the domain name and indicates that $columbia$ is an educational institution.
Electronic Mail Address
#ther networs may use di""erent electronic mail addressing schemes within their own networs. 6o be used in Internet e7mail, these addresses o"ten need to be modi"ied. 9or eample, within
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6o con'ert this to an address that can be used on the Internet, the comma is changed to a period and the number ser'es as the username. 6he domain name is compuser'e.com, so the Internet address would be1 5:02>.34Dcompuser'e.com
3.URs
U! stands "or Uni"orm esource !ocator. U!s are used to identi"y speci"ic sites and "iles a'ailable on the World Wide Web.
6he structure o" a U! is1 protocol1@@ser'er.subdomain.top7le'el7 domain@directory@"ilename *ot all U!s will ha'e the directory and "ilename. 6wo eamples1 http1@@www.healthyway.com@eercise@mtbie.html gopher1@@gopher.state.edu@ URs
-imilar to an e7mail address, a U! is read lie a sentence. 9or eample the U! http1@@www.healthyway.com is read as $http colon "orward slash "orward slash www do t healthyway dot com$. In S!mmary"
Internet addressing is used to identi"y people, computers, and Internet resources. Using the Internet re%uires an understanding o" di""erent addressing schemes. People are identi"ied with electronic mail addresses.
