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This session just remembering of a part of 7 OSI Layers, emphasis on 3th layer from the bottom. Exactly that is a Network Layer.

We are realize that almost dirty hand of an engineer network will do about Application Layer and Network Layer. So how about the other ones? in the real life, almost all layers except application and network layer are wrapped by hardware and software, they handled by industries manufacture of network peripherals and we don't care about that. We are required to know how to use it instead how the system works exactly.

As your consideration we know 2 kinds of addressing network:

• Physical Address (MAC Address) - it is classified as Data Link Layer
• Logical Address (IP Address) -  it is classified as Network Layer

Actually every network interface (network interface card or wireless) has a unique ID, we call a MAC Address which embedded in their hardware. But human can not read/remembering easily (example of MAC Address: 00-19-D2-8B-5D-FF), we can not manage it or create a segmentation of the network. Imagine, if you send data using MAC, how many MAC in the world, you must broadcasting the data packet to all around the world. That is make a crowded traffic, slow and not efficient. That is way we use Logical Address (IP Address) to transform MAC into IP and vice versa.

IP Address
The Internet is an entire network of interconnected computers in the world. In order to communicate and exchange data, between these computers requires the address as the identity of the identifier. That address is globally called the IP Address.

IP address is easy to use, easy to read and network segmented. Every network device (ie. smartphone, laptop, tablet, PC, etc) has an IP address to identify of the host to connected between others using TCP/UDP protocol.

An IP address is not actually assigned to a computer unit, but to a Network Interface inside that computer. For example, a computer / CPU may have two network interfaces that have two IP addresses. On the CPU The additional network interface is usually a Lan Card.

In a Computer Network, IP Address must be unique, should not be exactly the same as the IP on the other interface. It is intended to avoid any data transmission errors.
There are two types of IP Address: IPv4 (32bit )and IPv6 (128bit). But now we just focus on IPv4, for the next explanation i call it just IP. IPv4 is devided by four blocks decimal number which every block number is represented 8bit X 4 bloks = 32bit binary number. I give you a mention:

IP Address: 192.168.3.1 (dec) = 1100000.10101000.00000001.00000001 (bin)

An IP address is actually divided into two portions of the Network portion and Host portion. Network is part of the IP address that shows the address or id of a network. While the Host part is the part that shows the address of the computer in the network earlier.

Related to that, there are some rules, among others:

• All network addresses must be the same if we want the computer can be connected without the help of a router. 
• In a network there should be no host with the same value.

The IP Address consists of 32 bit binary numbers and that in an IP Address consisting of 32 binary bits there is a NETWORK-ID portion and a HOST-ID portion. NETWORK-ID is used for identification of network addresses, so if other networks want to communicate with our network, just go to the Network ID.