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Lesson on IP addresses for Bill

Mar 14, 2006 01:35 PM
by krsanna

Bill - Here's something that'll keep you busy for a while.  It 
includes some information on how IP addresses can be faked with 
proxies, and that sort of thing.  This may be right up your alley.


In computer networking, an IP address (internet protocol address) is 
a unique number that devices use in order to identify and 
communicate with each other on a network utilizing the Internet 
Protocol standard. (Sometimes this is shortened to just "IP" as 
in "My IP is A.B.C.D".) Any participating device  including 
routers, computers, time-servers, printers, internet fax machines, 
and some telephones  must have its own globally unique communicable 

IP is a network layer protocol in the internet protocol suite and is 
an upper layer protocol that also provides globally unique addresses 
(e.g., MAC address for ethernet) but two of these addresses will not 
necessarily be able to communicate to each other. IP adds a service 
on top of these data link layer protocols  through the use of an IP 
address  that provides the ability to uniquely identify with and 
communicate with any other device on the network.

In other words, an IP address is like a full address for postal mail 
while a MAC address is just the house number. For example, there are 
many addresses with a house number of 123 but there is only one 
address for 123 Main Street, Anytown, California, United States. 
Simply mailing something to "123" will not get it there but "123 
Main Street, Anytown, California, United States" is a globally 
unique address.

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; however, dynamically-
assigned IP addresses can make this difficult.

Since IP addresses are not easy to remember, the Domain Name System 
provides the ability to map domain names (e.g. to 
an IP address (

Contents [hide]
1 Dynamic vs. static IP addresses 
2 IP version 4 
3 IP version 5 
4 IP version 6 
4.1 Addressing 
5 See also 
6 External links 

Dynamic vs. static IP addresses
There are two methods to assigning IP addresses to computers: 
dynamic and static.

Static IP addresses are used primarily for servers so that they 
don't appear to "move" while non-servers are usually assigned 
dynamic IP addresses. Most dynamic IP address users are users of 
internet service providers (ISPs) since not all the users of an ISP 
are online at one time and the ISPs can "get away" with not having 
enough IP addresses for each user.

In order to use a dynamic IP address, a service such as Dynamic Host 
Configuration Protocol (DHCP) is used to assign addresses 
dynamically to devices as they request them. If a static address is 
used, it must be manually programmed into parameters of the device's 
network interface. (It is also possible to "fake" static IP address 
assignments through DHCP by assigning the same IP address to a 
computer  and no other  each time it is requested.)

IP version 4
Main article: IPv4#Addressing 
IPv4 uses 32-bit (4 byte) addresses which limits the address space 
to 4,294,967,295 possible unique addresses. However, many are 
reserved for special purposes such as private networks (~18 million 
addresses) or multicast addresses (~1 million addresses). This 
reduces the number of addresses that can be allocated as public 
Internet addresses and as the number of addresses available is 
consumed, an IPv4 address shortage appears to be inevitable in the 
long run.

This limitation has helped stimulate the push towards IPv6, which is 
currently in the early stages of deployment and is currently the 
only contender to replace IPv4. It is also sometimes impossible to 
track someone's real IP because they can use Internet proxies, in 
which they can fake that they are from a different country

IP version 5
What would be considered IPv5 existed only as an experimental non-IP 
real time streaming protocol called ST2, described in RFC 1819. In 
keeping with standard UNIX release conventions, all odd-numbered 
versions are considered experimental, and this version was never 
intended to be implemented; the protocol was not abandoned. RSVP has 
replaced it to some degree.

IP version 6
In IPv6, the new (but not yet widely deployed) standard protocol for 
the Internet, addresses are 128 bits wide, which, even with generous 
assignment of netblocks, should suffice for the foreseeable future. 
In theory, there would be exactly 2128, or about 3.403  1038 unique 
host interface addresses. If the earth were made entirely out of 1 
cubic millimeter grains of sand, then you could give a unique 
address to each grain in 300 million planets the size of the earth. 
This large address space will be sparsely populated, which makes it 
possible to again encode more routing information into the addresses 

A version 6 address is written as eight 4-digit hexadecimal numbers 
separated by colons. For readability, addresses may be shortened in 
two ways. Within each colon-delimited section, leading zeroes may be 
truncated. Secondly, one string of zeroes (and only one) may be 
replaced with two colons (::). For example, all of the following 
addresses are equivalent:

Global unicast IPv6 addresses are constructed as two parts: a 64-bit 
routing part followed by a 64-bit host identifier.

Netblocks are specified as in the modern alternative for IPv4: 
network number, followed by a slash, and the number of relevant bits 
of the network number (in decimal). Example: 12AB::CD30:0:0:0:0/60 
includes all addresses starting with 12AB00000000CD3.

IPv6 has many improvements over IPv4 other than just bigger address 
space, including autorenumbering and mandatory support for IPsec.

Further reading: Internet RFCs including RFC 791, RFC 1519 (IPv4 
addresses), and RFC 2373 (IPv6 addresses).

See also
MAC address 
Regional Internet Registry 
African Network Information Center 
American Registry for Internet Numbers 
RIPE Network Coordination Centre 
Asia-Pacific Network Information Centre 
Latin American and Caribbean Internet Addresses Registry 
Subnet address 
Geolocation software 
External links
Introduction to geolocation by IP address 
Articles on CircleID about IP addressing 
IP Spoofing: An Introduction 
IP-Address Management on LANs - article in Byte magazine 
Introduction to IP Address Allocation 
Community project to geotarget IP addresses 
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