Figure 1. Sample of a network
connection for an ISP
If
we looked at the diagram, our computer is assigned a local IP address by our
ISP for Internet communication, e.g. 192.168.2.1.
When
we perform a remote access to another computer or server, our local IP address
could be included in an Internet packet along with the global ISP’s IP address.
This is to ensure that the return packet knew to route back to our ISP, and
then our computer.
A
typical IP address is 12 digits, i.e. 6 bytes.
If
we encoded our local IP address in 3 characters or 3 bytes, we would save 3
bytes in communications. 3 bytes is 256 x 256 x 256 possible combination, i.e.
ISP could offer unique connection to 16,777,216 computers within their network.
Let’s
say our computer is temporarily assigned with a code ABF instead of 192.168.201.165. The
ISP could insert this code, ABF, in the database, and send out a message to the
gateway with its IP plus ABF as returned IP address, e.g. 265.378.109.243 + ABF
instead of 265.378.109.243 + 192.168.201.165 in an IP packet. The Internet
gateway only needs to route the return packet to 265.378.109.243, where the
packet would be decoded and delivered to 192.168.201.165 based on the internal code
ABF.
Similarly
the Internet gateway could encode the IP address of its internal ISP server
address before sending a packet out with its IP address and code of the internal
ISP.
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