Why IP Address ???

Why IP address is needed ???
I believe this is the first question every guy who starts wit networking will come across…Even I had same doubt..like everyone, I tried to google out..but everywhere I could see lots of answers  like it is layer3 addressing, logical address etc.
But I wanted the actual reason why IP address came into picture. We could have used MAC address to route.
Here it is the answer which I found out. Please correct me if I am wrong.
Suppose there are 2 networks each having a gateway routers R1 and R2. These gateway router is connected via serial cable a shown below.


Suppose Network 1 and Network 3 contains 100 devices each, each having unique MAC address. Now Router R1 and Router R2 has to store 100 entries in their routing table. Now, the router exchanges the routing info using different routing protocols like RIP,OSPF etc..So no. of entries in routing table in each router are 200.

Now Firstly, Think of Internet routers which contains millions of devices. It means each router in internet should contain entries for all the devices around the world…Ufff !!!.                                          It is highly impossible which requires hell lots of memory in the router and lookup routes will be a tedious job.

Secondly, Just imagine bandwidth used to exchange this Routing information. ufff, It will be very high.

Thirdly, Suppose if one machine goes down, that information needs to be exchanged by all the routers in the Internet. If that machine comes up again, the information needs to be exchanged by all the routers in internet again. This leads to very low performance network as there will be tremendous amount of control traffic in internet.
All these 3 reasons are definitely not acceptable in our traditional network as well. These are the main reasons to come up with IP address or logical address.
If we consider our previous example itself, Network 1  has one network address say Network 3 has a network address say  Router R1 and router R2 will exchange only one network address.  Router A will tell to router B that It knows how to reach Similarly router B also does.
So each router will be having only 2 entries in this case.
In this case, Router doesn’t need to advertise their routing updates when a single machine in network goes down.  Only if whole network goes down, update has to be sent across all the routers. Basically, hard-coded MAC addresses can’t be grouped like we group in IP Address.

So, These are the main reasons for coming up with the concept of IP address and this is how, IP address(logical address) solve the above mentioned problems which would have caused if we would have used MAC address to route packets.

Please correct me if I am wrong in any place. Feedback is highly appreciated. Hope it was helpful.

See you guys with my next post.
Stay tuned !!!