The Internet Protocol Suite was originally developed by the Defense Advanced Research
Projects Agency (DARPA) and then included with the Berkeley Software Distribution of Unix.
IP version 4 is the most commonly used version, however there is a slow migration around the work to
IP version 6. Internet Protocol works by breaking up data into datagrams for transfer across almost
any Layer 2 medium (LAN, MAN or WAN). The datagrams are then reassembled at the destination.
A number of RFCs have been written that give an overview of IP e.g.
- Encapsulating IPv4 within Ethernet
Routers are the devices that have the intelligence to examine the IP addresses within the datagrams to determine
where next to send the received datagram. Because routers are able to connect to different media such as Frame Relay, ATM,
Ethernet etc. they have the ability to strip off the link layer header and place the datagrams in other link layer headers.
This is done on a hop-by-hop basis and the decision process relies on the routing tables that each router builds
for itself. MPLS technology operates differently in that the path of the datagram is determined right at the outset rather
than a haphazard hop-by-hop mechanism.
A device on the local network will send a datagram to a remote IP destination by using the local MAC layer addressing as follows: