Encoding local IP address

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.