IP was created as a way to hide the complexity of physical addressing by creating a virtual addressing scheme that is independent of the underlying network. IP does not ensure that data is delivered to the application in the appropriate order; that responsibility is left to upper-layer protocols such as TCP and UDP.

IP is a connectionless, Network-layer protocol.

An IP address is 32 bits long. The bits can be broken down into four bytes. Each byte is expressed in decimal form and separated from other bytes by a dot (that is, x.x.x.x). This is called dotted-decimal format. Each bit within a byte carries a binary weight (starting from left to right) of 128, 64, 32, 16, 8, 4, 2, 1. If you add up these values, you get a range of 0-255 for each byte.

For example, one byte can be translated from binary format to decimal format as follows:

IP addressing has been broken down into five separate classes based on the number of maximum hosts required by the network.

IP Address Classes

You can see from above figure that each address class contains a network portion and a host portion. The network portion identifies the data link that is in common with all the devices attached to that network. The host portion uniquely identifies an end device connected to the network.

Private IP Addresses

Private address space is not recognized by the Internet and can be used by anyone for use within a private network. Public address space, on the other hand, is a unique address that is assigned to a company. Within Classes A, B, and C the following ranges have been defined as private.

Address Masks

The network mask is used in conjunction with an IP address to delineate the network portion of an IP address from the host portion. Each major network address within its designated class has a standard network mask.