Originally published on JS PACS, March 5, 2009. Part of the PACS IT Skills series. The diagram from the original post did not survive the archive.
The IP address, or Internet Protocol address, is an address assigned to a computer so that it can talk to other computers on a network. An address needs to be unique to the network segment it is on, but that same address can exist on another network. A few addresses are designated to be unique to the world and exist only once.
When troubleshooting network issues, such as an image that won’t send to the PACS server, you can use the ping utility, which uses the IP address. It simply sends a small packet of information to another computer, and if the other computer receives that ping, meaning it is on the network and working, it sends a response back telling you it is alive.
If it helps to visualize, the address of a device can be compared to your street address, which is unique to your town but not unique to your state or country. There may be many 1035 Union Street addresses in the country; consider each town its own network segment.
This protocol is found on the third layer of the OSI model.
An IP address is built from four octets (eight binary digits each), each octet being one byte in length. An entire address is therefore four bytes long.
In an upcoming article, we’ll review the various classes of networks and how they work into subnets.