Sign In Sign-Up

Welcome!

Close

Would you like to make this site your homepage? It's fast and easy...

Yes, Please make this my home page!

No Thanks

  Don't show this to me again.

Close

How The Internet Works

RESOLUTION: The Federal Networking Council (FNC) agrees that the following language reflects our definition of the term 'Internet'.

'Internet' refers to the global information system that :

(i) is logically linked together by a globally unique address space based on the Internet Protocol (IP) or its subsequent extensions/follow-ons;

(ii) is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or other IP-compatible protocols; and

(iii) provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein.

- Federal Networking Council (FNC), October 24, 1995.

The Internet is a packet-orientated network. That means that the data you transfer is divided in packets. This principle is not new, it was already used in the 1960s. So what happens when you transfer data across the Internet's various networks?
The networks are linked by special computers, the so-called Routers. A Router checks where your packet (your data) goes and decides in which direction to send it. Of course not every Router is linked with every other Router, they just decide on the direction your data takes.
So if the Routers know where the data is going, there must be some kind a address. Of course, there is an address, namely the IP - protocol. As I mentioned above, the data transferred with IP is divided in packets. This is handled by another protocol, the TCP.
It was soon discovered that the IP - addresses (that are, in fact, just numbers) are of course easy to handle for computers, but not for us humans. So the Domain Name System was introduced in 1984.
This was a brief description of how the Internet functions. If you want to read more, I strongly encourage you to check out the glossary information on DNS and TCP/IP.

IP Addresses

Present common carrier communications networks... use links and concepts originally designed for another purpose voice...

Time division multiplexing appears so natural to data transmission that we might wish to consider an alternative approach, a standardized message block as a network interface standard. While a standardized message block is common in many computer-communications applications, no serious attempt has ever been made to use it as a universal standard.

A universally standardized message block would be composed of perhaps 1024 bits. Most of the message block would be reserved for whatever type data is to be transmitted, while the remainder would contain housekeeping information such as error detection and routing data.

Every computer has a unique IP address. This address gives the TCP/IP networking protocol the identifying information it needs to route packets from one computer to another across the net. The following sites will display your current IP address:

Privacy.net
Cyberarmy.com

The following subsections provide more information:

Address format
Address allocations
Lookup databases
More information
Address Format. Your computer's IP address serves the same purpose as a house address -- it uniquely identifies your computer so that other computers can find it.

Your unique IP address is used whenever you use electronic mail, the world wide web, or any Internet technology to communicate with another computer. The IP address of the source and destination computers are stored in the header of every packet of information that flows across the net.

An IP address is made up of four numbers between 0 and 255, commonly shown separated by periods. For example, your computer's IP address might be 238.17.159.4, shown below in the human readable decimal form, and in the binary form used on the Internet.

Example IP Address

Decimal:
238 . 17 . 159 . 4

Binary:
11101110 . 00010001 . 10011111 . 00000100

Each of the four numbers in an IP address may be between 0 and 255, so there are more than 4 billion different possible different IP addresses:

4,294,967,296 = 256 * 256 * 256 * 256

Address Allocations. The Internet Assigned Numbers Authority manages the allocation of IP addresses to different organizations in various sized blocks. The IANA IP Address Service page provides a focal point for this world wide IP address management.

A list of the allocations of IP address blocks can be found at the Internet Protocol Address Space site. Most of the address blocks have been allocated to research, education, government, corporations, and Internet Service Providers, who in turn assign them to the individual computers under their control. A few addresses are reserved for future or special use. The top-level allocations of these blocks of IP addresses are described in Request For Comments 1466.

If you connect to the Internet over a phone line, then your IP address is probably assigned dynamically from an available pool of addresses each time you log on. If your computer is permanently connected to an Internet network, such as at an office, then your computer's IP address may be permanently assigned, or may be assigned each time you boot your computer.

You can find out your IP address on a Windows computer by opening an MSDOS window (or "Start / Run") and typing "winipcfg" or "ipconfig", and on a Macintosh computer by checking your Network control panel.

When your computer needs to contact another computer, it first looks up the computer's IP address using the Domain Name Service. It then puts that IP address in the headers of the packets it wishes to send to the computer, and sends the packets to the nearest router. The router uses the IP address and one of the Internet routing protocols to send the packets through the net to the destination computer.

Lookup Databases. To find out more information on any particular IP number, you can look it up in one of the following databases. You may have to try more than one to find the right database that has the information on that particular address:

American Registry for Internet Numbers
European IP Address allocations
Asia Pacific IP Address allocations
US Military Whois
US Government Whois

Packet Switching

The Net interprets censorship as damage and routes around it. Communicating information in packets enables construction of switching systems with great flexibility and fault tolerance.

Like the development of hypertext, packet switching seems to have been an idea that wanted to be discovered, and was independently developed within a few years by different people. Packet switching was a paradigm shift from the prevailing view of communications networks as dedicated, analog circuits to a new model of discontinuous, digital systems. The following sections provide more information:

Routing

Routing is the method by which the host or gateway decides where to send the datagram. It may be able to send the datagram directly to the destination, if that destination is on one of the networks that are directly connected to the host or gateway.

However, the interesting case is when the destination is not directly reachable. In this case, the host or gateway attempts to send the datagram to a gateway that is nearer the destination. The goal of a routing protocol is very simple: It is to supply the information that is needed to do routing.

Once you have packet switching and IP addresses, you have an infrastructure that routing algorithms can use to get packets from one computer to another. The following subsections provide more information.

Routers, The special computers that switch packets from one network to another. Interior Gateway Protocols . The routing protocols used within local area networks.

Domain Names

For example, consider self-adaptation to station location. A station, Able, normally transmitted from one location in the network...

If Able moved ... all he need do to announce his new location is to transmit a few seconds of dummy traffic. The network will quickly learn the new location and direct traffic toward Able at his new location.

Domain names are the alphabetic names used to refer to individual computers on the Internet. The Domain Name Service (DNS) is a network of servers that map the domain names to their current IP addresses, thereby enabling one computer to find and communicate with another on the net. The following sections provide more information:

Domain Names -- Top-level, second-level, third-level, and country domains.
Domain Name Service -- The collection of name servers that run the net.
Domain Name Aliases -- How to write domain names with numbers.
DNS Information -- RFC's and other documentation.
You can get your own domain name from an accredited registrar.

Architecture

The Internet architecture is based on a hierarchy of networks.

The network topology section provides a list of sites that graphically portray the Internet network architecture, which consists of a series of smaller networks connecting to larger networks. People at home and local area networks in offices connect to local providers, which connect to regional networks, which connect to national networks, which connect to the largest providers on the Internet backbone.

An Internet packet will go as far up the network hierarchy as necessary to get to its destination. The networks at each level pay the next level for the bandwidth they use over the course of each month. The home user pays the ISP, which pays the regional provider, which pays the national provider, which pays the company it connects to on the backbone.

Bandwidth provided by one network to another may be priced at a fixed cost for a certain ceiling, like 2 megabits per second, or by a variety of per use methods that can be thought of as a cost per gigabyte. Due to economies of scale, the costs for bandwidth drop dramatically at each level, and can be purchased for under $5 per gigabyte in quantity from the largest providers.

The Internet backbone is a very high bandwidth network run by large companies and organizations, and connects internationally through underwater cables and satellite links. Traffic is exchanged at large Network Access Points (NAP's). Five of the largest NAP's in North America are in Chicago, New Jersey, San Francisco, San Jose, and Washington, D.C. Two of these NAP's are also called Metropolitan Area Exchanges (MAE's).
The following sites maintain indexes of NAP sites:

BNIX List of IX in Europe

EP.net Exchange Point Information

European Internet eXchange points -- Clickable Map

Manning's Exchange Point Information

MCI WorldCom MAESM Information

RIPN IX

Ethernet

Samuel B. Morse's regenerative repeater invention for amplifying weak telegraphic signals has recently been resurrected and transistorized.

Morse's electrical relay permits amplification of weak binary telegraphic signals above a fixed threshold. Experiments by various organizations (primarily the Bell Telephone Laboratories) have shown that digital data rates on the order of 1.5 million bits per second can be transmitted over ordinary telephone line at repeater spacings on the order of 6,000 feet for #22 gage pulp paper insulated copper pairs. At present, more than 20 tandemly connected amplifiers have been used in the Bell System T-l PCM multiplexing system without retiming synchronization problems.

There appears to be no fundamental reason why either lines of lower loss, with corresponding further repeater spacing, or more powerful resynchronization methods cannot be used to extend link distances to in excess of 200 miles. Such distances would be desired for a possible national distributed network. Power to energize the miniature transistor amplifier is transmitted over the copper circuit itself.

Ethernet is a physical transmission standard for digital radio frequency communication over copper wire networks. Ethernet networking is the most common physical networking standard. It supports TCP/IP networking seamlessly, and provides an inexpensive, simple, high bandwidth method for interconnection of local computers. Ethernet solved the all important "last mile" problem, and remains the standard method of connecting personal computers to the Internet at the office, and at home over high bandwidth connections.

In the late 1960's, engineering developments were rapidly improving integrated circuit development and computer display monitors. In order to complete the technological triangle, Xerox PARC developed Ethernet networking, providing a fast, simple, predictable local area networking standard. Robert Metcalfe and David Boggs led the development.

Robert Metcalfe got the idea for the Ethernet protocol when he read a 1970 computer conference paper by Norman Abramson of the University of Hawaii about the packet radio system called ALOHAnet linking the Hawaiian Islands. Each node in ALOHAnet sent out its messages in streams of separate packets of information. If it didn't get an acknowledgment back for some packets because two radios were broadcasting at the same time, then the missing packets were considered "lost in the ether".

When a packet was lost in the ether, the node would rebroadcast them after waiting a random interval of time. Because of this randomness, problems with collisions were quickly resolved except under the highest traffic loads. On average, the network rarely had to retry more than once or twice to get all of the packet to the destination, which was more efficient than trying to implement a complex coordination system to prevent collisions in the first place.

Abramson's design showed that, while it worked well, ALOHAnet reached its maximum traffic load at only 17% of its potential maximum efficiency, because of a great increase in collisions at higher loads. Metcalfe chose this problem for his computer science thesis, and, as a graduate student at Harvard, showed that you could use mathematical queuing theory to achieve 90% efficiency of the potential traffic capacity without being locked up by the packet collisions.

Ethernet is now by far the most common local area network. Metcalfe went on to found 3Com in 1981, a maker of Ethernet network cards and other communications products, and now one of the largest telecommunications companies in the world.

The first version of the Ethernet standard had a bandwidth of 2.94 Mbps, or about 300,000 characters a second. The current version is standardized as IEEE 802.3, and provides a bandwidth of 10 Mbps or about 1,000,000 characters a second, over normal twisted pair telephone wires, and is the most commonly deployed local area networking standard. Recent advances in the technology have resulted in development of 100 Mbps and 1 Gbps Ethernet standards, which are increasingly being deployed for high bandwidth environments.

Every Ethernet network interface has a unique MAC address. RFC 826 describes how to obtain an IP address from an Ethernet MAC address.

Bob Metcalfe wrote Request For Comments 602, The Stockings Were Hung by the Chimney with Care, in December, 1973, including descriptions of incidents of hacking only four years after the birth of the ARPANET.

| Back |