As datagrams travel from one gateway to another, each gateway routes the datagram based on the network number in the datagram's destination address. Only the gateway on the same network as the destination uses the local part of the address in forwarding a datagram. That is, when the datagram reaches a gateway that connects to the destination address, the gateway uses the local part of the address to forward the datagram to the appropriate host. Thus, Internet addresses handle both large and small networks. In the ISO world, addresses are of varying format and length and just extracting the address from the packet may not be straightforward.
Internet addresses can also refer to broadcast addresses.
Of course, if the underlying network technology doesn't support broadcasting, one can't broadcast Internet datagrams either. Network addresses are written using dotted decimal notation. Each address consists of 4 bytes, and each byte is written in decimal form. Internet addresses refer to network connections rather than hosts. Gateways, for instance, have two or more network connections and each interface has its own IP address.