Download What is Internet addressing

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
URLs
In general, Internet addressing is a systematic way to identify people, computers and
Internet resources.
On the Internet, the term "address" is used loosely. Address can mean many different
things from an electronic mail address to a URL.
1.IP Address
An IP address is a unique number that identifies computers on the Internet; every
computer directly connected to the Internet has one. Every client, server and network
device must have a unique IP address for each network connection (network interface).
IP addresses are conceptually similar to phone numbers, except they are used in LANs
(Local Area Network), WANs (Wide Area Network), and the Internet. Because the
numbers are not easy for humans to remember, the Domain Name System provides a
service analogous to an address book lookup called "domain name resolution" or "name
resolution". Special DNS servers on the internet are dedicated to performing the
translation from a domain name to an IP address and v.v.
An IP address consists of four numbers separated by periods. Each number must be
between 0 and 255.
An example is: 204.81.205.32
The format of an IP address is a 32-bit numeric address written as four numbers separated
by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP
address.
Within an isolated network, you can assign IP addresses at random as long as each one is
unique. However, connecting a private network to the Internet requires using registered
IP addresses (called Internet addresses) to avoid duplicates.
The four numbers in an IP address are used in different ways to identify a particular
network and a host on that network. Four regional Internet registries -- ARIN, RIPE
NCC, LACNIC and APNIC -- assign Internet addresses from the following three classes.
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Class A - supports 16 million hosts on each of 126 networks
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Class B - supports 65,000 hosts on each of 16,000 networks
Class C - supports 254 hosts on each of 2 million networks
Format. An IP address is made up of four bytes of information (totaling 32 bits)
expressed as four numbers between 0 and 255 shown separated by periods. For example,
your computer's IP address might be 238.17.159.4, which is shown below in humanreadable decimal form and in the binary form used on the Internet.
Example IP Address
Decimal:
Binary:
238 . 17 . 159 . 4
11101110 00010001 10011111 00000100
Each of the four numbers uses eight bits of storage, and so can represent any of the 256
numbers between zero (binary 00000000) and 255 (binary 11111111). Therefore, there
are more than 4 billion possible different IP addresses in all:
(Internet Protocol address) The address of a device attached to an IP network (TCP/IP
network). Every client, server and network device must have a unique IP address for each
network connection (network interface). Every IP packet contains a source IP address and
a destination IP address.
Static and Dynamic IP
Each device in an IP network is either assigned a permanent address (static IP) by the
network administrator or is assigned a temporary address (dynamic IP). Depending on
one's Internet connection the IP address can be the same every time one connects (called
a static IP address), or different every time one connects, (called a dynamic IP address).
In order to use a dynamic IP address, there must exist a server, which can provide the
address. IP addresses are usually given out through a server service called DHCP or the
Dynamic Host Configuration Protocol. If a static address is used, it must be manually
programmed into parameters of the device's network interface.
Routers, firewalls and proxy servers use static addresses. Client machines may use static
or dynamic IP addresses.In routers and operating systems, the default configuration for
clients is dynamic IP .
Dotted Decimals
IP addresses are written in "dotted decimal" notation, which is four sets of numbers
separated by periods; for example, 204.171.64.2. If you knew the IP address of a Web
site, you could enter the dotted decimal number into your browser instead of the domain
name .The traditional IP address uses a 32-bit number that defines both the network and
the host computer. The network class determines how many of the 32 bits are used for the
network address, leaving the remaining bits for use as the host number. The host number
can be further divided between subnetworks and hosts
Class A, B and C
Although the computer identifies the class by the first three bits of the address (A=0;
B=10; C=110), people identify the class by the first number in the address (see range
below). This class-based system has also been greatly expanded, eliminating the huge
disparity in the number of hosts that each class can accommodate
Class
A
B
C
Maximum
Maximum
Class
Number
Hosts
Number
of
per
Range
Networks
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 first divided between networks and hosts. The host bits are further
divided between subnets and hosts.
More detail
The Internet Protocol (IP) knows each logical host interface by a number, the IP address.
On any given network, this number must be unique among all the host interfaces that
communicate through this network. Users of the Internet are sometimes given a host
name in addition to their numerical IP address by their Internet service provider.
The IP addresses of users browsing the World Wide Web are used to enable
communications with the server of the web site. Also, it is usually in the header of email
messages one sends. In fact, for all programs that utilize the TCP/IP protocol, the sender
IP address and destination IP address are required in order to establish communications
and send data.
Internet addresses are needed not only for unique enumeration of hosted interfaces, but
also for routing purposes, therefore a high fraction of them are always unused or
reserved.
The unique nature of IP addresses makes it possible in many situations to track which
computer — and by extension, which person — has sent a message or engaged in some
other activity on the Internet. This information has been used by law enforcement
authorities to identify criminal suspects. The dynamically-assigned nature of many IP
addresses can make this more difficult.
Domain Name
Most computers on the Internet have a unique domain name.
Special computers, called domain name servers, look 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 example domain name is: healthyway.com
Domain names are easier for most people to relate to than a numeric IP address.
2.Electronic Mail Address
An Internet electronic mail, or e-mail, address is used to identify a person (or persons)
and a computer for purposes of exchanging electronic mail messages.
An example Internet e-mail address is: [email protected]
Internet e-mail addresses are read from left to right:
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"abc123" is the name of the person receiving or sending the message; this is
referred to as the username.
"columbia" is part of the domain name of the organization.
"edu" is also part of the domain name and indicates that "columbia" is an
educational institution.
Electronic Mail Address
Other networks may use different electronic mail addressing schemes within their own
networks. To be used in Internet e-mail, these addresses often need to be modified.
For example, within CompuServe an e-mail address consists only of two numbers
separated by a comma: 36547,891.
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To convert this to an address that can be used on the Internet, the comma
is changed to a period and the number serves as the username.
The domain name is compuserve.com, so the Internet address would be:
[email protected]
3.URLs
URL stands for Uniform Resource Locator. URLs are used to identify specific sites and
files available on the World Wide Web.
The structure of a URL is: protocol://server.subdomain.top-leveldomain/directory/filename
Not all URLs will have the directory and filename.
Two examples:
http://www.healthyway.com/exercise/mtbike.html
gopher://gopher.state.edu/
URLs
Similar to an e-mail address, a URL is read like a sentence. For example the URL
http://www.healthyway.com
is read as "http colon forward slash forward slash www dot healthyway dot com".
In Summary:
Internet addressing is used to identify people, computers, and Internet resources.
Using the Internet requires an understanding of different addressing schemes. People are
identified with electronic mail addresses. Computers are identified with IP addresses and
domain names. Resources and files available through the World Wide Web are identified
using URLs.