What is the current IP bit specification that uses addresses to identify hosts?

Answer 1

This can be answered in a couple of ways as it depends on if you are asking about the IP address or the way that IP addresses are subnetted. So, let me address both as well as give a little history.

When public addresses were first being assigned, a class system was used such that larger organizations may have been granted a Class A license, which meant that only the first octet was statically assigned while smaller organizations may have received either Class B or Class C licenses (with two or three octets statically assigned, respectively). So, what does this mean? It means that, for example, MegaCableTV may have received the Class A assignment of 24.x.x.x, which means that the company could use any and all addresses from 24.0.0.0 through 24.255.255.255, thus giving a total of 16,777,216 addresses for their use. It was originally thought that the 4,294,967,296 available addresses in the IP address scheme of four octets would be more than enough for the foreseeable future, so giving away such large IP address ranges was not much concern...until it became obvious that "everyone" in the world wanted to get into the internet as the new "game in town."

So, eventually the IP addressing system based on Classes was dropped and Classless Internet-Domain Routing (CIDR) became the standard of the day. This allowed various sizes of subnetworks (subnets) to be designated by a varied size of subnet mask. (What is a subnet mask, you ask? It is what determines how many addresses are allowed in a certain network address scheme. With Class A, the subnet mask was 255.0.0.0 (also sometimes expressed as /8, as in 24.0.0.0/8 in our above example of the fictional company MegaCableTV.) So, for example, a company, say another fictional Internet provider of MyFavoriteDSL is allowed to use the IP address range of 167.20.0.0 through 167.23.255.255 would be given a subnet mask of 255.252.0.0 or the IP address range could be expressed as 167.20.0.0/14. This allowed for more addresses to be available once again as "wasted" addresses could be "reclaimed" for use by others but it still was not enough to stem the tide of the billions of people and companies around the world having more and more devices that needed to be assigned public IP addresses.

The next step was to come up with a new IP address scheme that would allow more addresses than could be conceivably used at any point in the long-distant future. The concept of IPV6 was born and the old addressing standard became referred to as IPV4.

IPV6 uses a total of 128 bits (16 bytes) to compose addresses as opposed to only 32 bits (4 bytes) used with IPV4 addresses. (Because of IPV4's structure of each number being represented by eight bits, each number is referred to as an octet.) The IPV6 address is divided into eight groups of four hexadecimal numbers (numbers 0 through 9 and A through F), such as 18AF:029E:ABBA:CAB3:DA67:4501:0274:0001. This extreme expansion of the size of the address allows for a total of 3.402 x 10^38 addresses. This means that there are approximately 7.923 x 10^28 times as many addresses in IPV6 than IPV4. It shall be a long time before we run out of IPV6 addresses.

At this time in 2017, most of the Internet still relies on IPV4 but IPV6 is coming along and is destined to replace IPV4 in time.

Now, if the question that you meant to ask has to do with the already-touched-upon topic of subnet masks, then let me address that more fully at this time.

The subnet mask allows a router (or network engineer or other who needs to know the structure of the network) how the network in question is divided and what significant IP addresses can be expected. For example, if someone was using the private IP address range of 192.168.0.0 through 192.168.0.255 for their home network, the subnet mask would be 255.255.255.0 (or the network could be referenced to as 192.168.0.0/24). This would allow the router to know that the significant "automatically used" addresses of the range are 192.168.0.0 for the network's addresses so as to reference itself and 192.168.0.255 for the network's broadcast address (something that is to be sent to every station regardless of what its specific IP address might be). As the router itself needs an address, this means that a total of 253 addresses are available for devices on the network: printers, computers, servers, tablets, cellular phones, managed network switches, etc.

The size of the subnet mask can vary, depending on the needs of the network in question. The most common in use today, however, is the 24-bit mask of 255.255.255.0 as most installations are home users and small businesses. It also is commonly used in larger businesses so as to help keep cross-traffic between departments, computer labs, or other divisions of the organization to a minimum. The purpose for doing this is to keep the traffic clean on the network cabling so that communication is more efficient and allows for faster response to requests.

To explain this further, let's presume for a moment that a building has the departments of human resources, accounting, motor pool, and food service within it. Now, while each department does have a reason to interface in some fashion (for example, the motor pool could arrange for a vehicle to carry the prepared food to remote facilities and the accounting department could insure that the purchase orders for parts for the vehicles are properly written and recorded), the network traffic that they generate internally does not need to be going back and forth between the various other departments. So, subnetworks can be configured so as to keep the communications destined only for the one department's resources will see those transmissions and they will not be sent over the cable plant to the other departments unless the transmission in question is specifically addressed to a device on the other subnetwork. This increases efficiency and allows for at least a first step in better data security. (There is much more involved in data security than this, of course, but that is a subject for another question and another time.)

I hope this helps address your query. If you have any other questions or if any/all of this is about as clear as mud on a moonless night, feel free to drop me a line.