Hello Muhammad
This is an excellent question and it shows that you are thinking deeply about these concepts, and that’s great. So, the IP protocol is a connectionless protocol. This does indeed mean that each packet is treated independently. In other words, each packet is sent and forgotten. There is no mechanism that will check to see if IP packets have arrived safely, in order and in a timely manner. (this is taken care of at higher layers of the OSI model, like TCP and Application)
Now an IP packet can theoretically have a maximum size of just over 65000 bytes. However, an Ethernet Frame is typically restricted to a size of 1500 bytes. These numbers can be adjusted, but the point is that the size of the IP packet can be larger than the frame into which it is to be encapsulated. To deal with such cases, there is a mechanism called fragmentation. Fragmentation allows a single IP packet to be fragmented or broken into several pieces, each having its own IP header and each placed within a frame. When this occurs, there are several fields in the IP packet header that are used to keep track of such packet pieces. These include the More Fragments flag that indicate that the packet is indeed part of a larger fragmented packet as well as a fragment offset that helps to correctly put the fragments back together.
When these fragments reach their destination and deencapsulation takes place, they are put back together appropriately.
Now this does not change the fact that each individual IP packet is sent along its way on the network completely independently of any other. Each has its own header, its own source and destination IP and is at the mercy of the IP protocol. Because of this, fragmented packets may not arrive in order, but buffers at the destination keep fragments in memory until all arrive and can be reassembled and further deencapsulated. However, even fragmented packets can be lost, and if this happens, the received fragments of the incomplete packet are eventually discarded.
So fragmentation does involve some relationship between fragmented IP packets, but ultimately, each is sent on its own independently of any other.
I hope this has been helpful.
Laz