The IPv4 protocol
assigns each device which is connected to the network a 32 bits number (IP
address), which should identify it uniquely.
The problem is that large ranges in the IP "address-space"
are reserved for different usages, or assigned to organizations which
don't use even a small part of the range .
Therefore, a new standard for the Network Layer, called
IPv6, which has a much larger address space, has been created, and is
fully supported by Linux, but it is not commonly used yet.