The internet layer then passes the packet, called a datagram, to the
data-link layer to be broadcast onto the local network.
If the message is destined for a computer not attached to the local network, the router that connects the local
network to another network will read the message. The router will rebroadcast the packet on the other network, and
by such process repeating, the message will find its way through myriad intervening networks to its destination.
The most popular network layer protocol is internet protocol (IP). Each computer attached to the internet
has a unique IP address. Most IP addresses today are 32 bits long (called IP version 4). With the enormous
growth in the use of the Internet, network experts see the need in the future for a larger address field in order to
accommodate a much larger number of computers on the internet. A new standard IP address called IP version
6 has an address field 128 bits long. Over time, more computers will begin using IPv6. In any case, the IP
protocol identifies both the source and destination computers by their IP addresses.
You may be surprised that the IP protocol, on which we all depend, is specifically an unreliable
protocol! IP simply builds datagrams and gives them to the link layer to send.
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