How many IP addresses are there?

120px-worldwidewebaroundgoogle How many IP Addresses are there?

Simple answer: 262,600,608,710,656, read as: 262 Trillion, 600 Billion, 608 Million, 710 Thousand and 656.

These are publicly available addresses that can be used for communicating between two devices over the network.

What is an IP address?

An IP address is a 48-bit number that identifies one participant in a two-way conversation over the Internet.

How is an IP Address written?

An IP address is written like this: 192.168.1.8 port 80. The valid range of the first four numbers is 0 to 255; the valid range of the last number is 0 to 65,535. This numbering scheme allows for 281,474,976,710,656 unique addresses — however, some are reserved for use by private and multi-cast networks, so only 262,600,608,710,656 are available for public use.

I should note here that most other references that you’ll see to the term “IP Address” do not include the port as part of the address.  With that more conventional definition, the number of IP addresses is 232,  giving an address count of 4,294,967,296 — that is, a little over 4 billion, rather than the 262 trillion number that I refer to.  Why do I use the larger number?  In fact, some fairly large part of the internet consists of corporate and institutional networks that use port-numbers to create distinct IP addresses using a technique called Port Address Translation.  So that’s why I include the ports in the overall IP Address count.

How is an IP Address used?

When two participants establish a conversation on the Internet, they exchange data in so-called Internet Protocol packets that consist of a prefix (called the “header”) and the data (called the “Payload”). The IP header contains the IP Address of the sender and the IP Address of the recipient for that data packet.

The Internet Protocol is a “hand-shake” agreement between the computers on the Internet that defines how data should be formatted and routed between computers.

I should clarify the term “participant”. I’ll use an example. Right now, my home computer is attached to the Internet and I have 8 windows open to different web-sites:
– A page from Google (The search web-site)
– A page from WikiPedia (The online encyclopedia web-site)
– A page from my web email
– A page from the Washington Conference center
– .. and more.
Each of these pages represents an Internet conversation between my computer and a different computer on the Internet. I’ve got 8 separate conversations, and thus my machine is a participant 8 times — meaning that I have 8 Internet addresses in use right now (for my machine) and 8 external internet addresses reserved for my use, one at each of the external machines that I’m conversing with. Generally, the first 4 numbers of the IP address (192.168.1.8 in my case) identify the machine, and the last number — the port number — identifies the conversation.

Are there enough IP addresses to go around?

The US Population is 303,824,640 (July 2008 est.  – from the World Fact Book, published on the web by the CIA).  From the US Census bureau, we get these figures, estimated as of today (prepared on February 15, 2009):
U.S. 305,823,230 (305 Million plus) World 6,760,726,213 (6 Billion, 760 Million, plus)

People are concerned that we will eventually run out of IP addresses. So they’ve come up with an extended addressing scheme that will support 2128 (about 3.4×1038) addresses. That is 34 followed 37 additional zeros:
340, 000,000,000, 000,000,000, 000,000,000, 000,000,000

The number name for each triad of 000’s, starting at the left: undecillion, decillion, nonillion, octillion, septillion, sextillion, quintillion, quadrillion, trillion, billion, million, thousands, and hundreds.

So read this as 340 undecillion. Should be enough, eh?  (I didn’t include the ports in this calculation!  To include the effect of the ports, mutiply 340 undecilion by 65,536.  I’ll leave that calcuation as a homework assignment for you.)

Prepared by Bob Monahon, 2/15/2009


A note about the image: This Wikipedia and Wikimedia Commons image is from the user Chris 73 and is freely available at http://commons.wikimedia.org/wiki/File:WorldWideWebAroundGoogle.png under the creative commons cc-by-sa 2.5 license.

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