How The Internet Works

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InterWhat?

The internet is managed by an international group called The Internet Society (ISOC). ISOC is a professional membership society that manages the infrastructure of the internet toward the goal of maintaining the viability and global scaling of the internet.

When a user connects to the internet, they're immediately connecting to a network, likely their own personal network. That network is their LAN (Local Area Network) and that connects to the ISP (Internet Service Provider). The ISP network connects to a NAP (Network Access Point) where several high-end networks connect and that traffic routes through what we call the internet backbone to 'the internet'. At each stop, the amount of data being transferred gets bigger and bigger.

Networks

A network is a series of computers connected to each other and/or electronic devices. Many networks are also connected to the internet; those without internet access are sometimes called intranet networks. Devices on a network commonly connect through ethernet (RJ-45) patchcords.

There are many types of networks, such as Local Area Networks (LAN - limited to small areas such as offices), Campus Area Networks (CAN - limited to a geographical area such as a campus), and Wide Area Networks (WAN - covering regional or national boundaries).

Networks can sometimes be compared to a map of roads (ethernet connections), buildings (computers/servers), traffic (information packets), etc.

IP Addressing

IP is short for 'Internet Protocol', which is the network and transport protocol used for exchanging data over the internet. There are three types of usable IP addresses: Class A, Class B and Class C. The class of an address changes based on how many hosts it supports and can be determined by the first octet.

Class A - Very large networks
Default Subnet: 255.0.0.0
IP Range: 1-126

Class B - Medium networks
Default Subnet: 255.255.0.0
IP Range: 128-191

Class C - Small networks
Default Subnet: 255.255.255.0
IP Range: 192-223

Reading an IP Address

For all intents and purposes, the IP address is analogous to the street address of a house – i.e. it is the location at which a computer will be found. This address gives us information about the 'neighborhood' the computer is located in and gets as specific as the individual 'house' (computer/device). An IP address is made up of four octets, for example: 131.128.10.112. So, in this case, the first two octets 131.128 tell us that its 'neighborhood' is the URI local area network (LAN). This address (the IP address) is assigned by the DHCP server (Dynamic Host Control Protocol) as long as the computer is requesting a dynamic IP address. The third octet is the 'Subnet', which pinpoints the network more precisely. A subnet may include an entire building (some buildings may have two subnets). The fourth octet, the host, pinpoints the address to the precise device that it's using. As such, the IP address becomes a complete route address. To review:

131.128 (URI) .10 (Keynes Hall) .112 (John Doe in room 15A)

131.128.x.x
On the URI network, 131 is the 'life is good' IP net. It means that a computer successfully obtained a valid IP address from the URI DHCP server and, if they're having network problems, it isn't DHCP related. In this case, if a user cannot access the internet, it is software related.

169.x.x.x
A 169 address means that the computer failed to contact the DHCP server. At its base root, failure to contact the DHCP server could mean several things. There is an interruption in the line between the computer and the DHCP server. This could be a bad cable, a bad port, or a bad NIC card. It could also indicate a virus interfering with network communication.

172.x.x.x
On the URI wireless network, a 172 indicates successful connection with the Access Point (AP). This does not always indicate that the user is able to surf the internet, because the IP assignment is done before user authentication. The user's signal must pass through the AP.

192.168.x.x
A 192 indicates a successful connection with a wireless router. This does not always indicate that the user is able to surf the internet, as the router must also be properly connected to the internet. If the router is incorrectly configured on a wired network, it may act as a DHCP server, sending out 192.168.x.x addresses on the wired network. This is known as a "rogue router".

10.x.x.x
A 10 IP address is commonly used as a private address (cannot connect outside an intranet) and is commonly applied as a static IP to printers and other personal networked devices. It is also the default configuration used by Apple wireless routers.

224.0.0.x
This specific type of address is not an IP address, but rather a multicast address that all routers (that respond to router discovery multicasts) will listen for and respond to.

x.x.x.1
This address is known as the gateway address on the network. Traffic passes through this point before leaving the subnet and travelling to a central node or the internet.

x.x.x.0
This address is reserved on every wired network subnet.

x.x.x.255
This address is reserved on every wired network subnet.

Common Operating Systems

Networks are generally created for the end-user; a person using a single computer to connect to a network or the internet. These computers connect to networks using ports, which define how traffic is sent and received.

These computers are based on operating systems ("OS") that allow the user to run software applications (many of these applications access specific ports to send and receive specific traffic to and from the network).

The most common operating system is made by Microsoft™ Windows™. The latest operating systems from Microsoft™ are "XP", "Vista" and "7". Also well known is the OS X operating system by Apple™. And many servers run a version of Linux, such as Ubuntu or Gentoo.


Related Links:

 http://www.iana.org/assignments/multicast-addresses
 http://en.wikipedia.org/wiki/Multicast_address
 http://en.wikipedia.org/wiki/Internet