IP address and MAC address

Why do we need IP address when we already have MAC address

[B]Question asked by visitor Muhammmed Hussain[/B]

hai
IP address is given to every system connected to the network.it is used to identify the system when connected to internet when msg has to be send.

whereas MAC is the hardware number given to the system by the company which deveops it .it is a standard format followed by all company.
this is also used to identify the system in network.

both IP and MAC are unique for each system.

if any change pls do inform me

MAC address is used at Datalink layer of OSI model which is typically assigned to devices by manufactures. IP address is the logical address assigned at Network layer of OSI model. In Ethernet LAN the MAC address is used to deliver the data to the device at the lower level even though we use IP address at higher level. If we type \\192.168.0.5\Files on a system having IP 192.168.0.10, the communication at lower level uses the MAC address of both systems ie 192.168.0.10 & 192.168.0.5. The whole process goes like this if both systems are in same Local Segment ie. not separated by router.
Suppose a user types \\192.168.0.10\Files on system A (192.168.0.5) to access Files Share on System B (192.168.0.10)
The system A will use the protocol ARP to find out the MAC address of system B. From the receiving first frame, the system A knows the MAC of system B. Then the communication between A & B will be going on using MAC address of both at lower level ie. Datalink.

Ip addresses are hiearchical while mac addresses are flat addresses and neworking application uses both the combination of these addresses if we use only mac addresses which is physical we have to create a huge database while ip addresses are logical it gives us the network addresses in which the computer is present then its subnet address thus router can easily locate the computer efficiently as it doesnot need to know all addresses and then find the mac addresses of the computer to have commincation on physical level

Basic:
ipaddress is logical address - identification of ur system, 32 bit address, unique inside the network, where mac address is physical address - hardware identification of ur interface (nic), 48 bit / 6 hexadecimal, unique all over. Technical:
if any packet comes out from the system, then the first packet should be the arp packet, which will identify the hardware address of the destination ipaddress (ur target ipaddress) and has the table to map both ipaddress and mac address. Then only the other communication between two computers will happen. Hardware address works in datalink layer - ipaddress works in network layer (verify osi layer model). So, when the packet from the source reaches the destination, it will reach the datalink layer first, confirms the mac address then move on to network layer, map with the ipaddress and then move to reach the user step by step. Ipaddress can be changed where mac address couldnot be. Just for simplicity, consider like this
for a student:
student name - student roll number - student public exam number
using the student roll number, u can identify the student name and student exam number. For a host:
hostname - host ipaddress - host mac address
using the host ipaddress, u can identify the hostname and mac address.
(dont compare deeply :p )

The Mac address is not a hierarchy one, but the IP address is.
This hierarchy is used to group the computers( in technical terms
network , sub-net , super-net). So that it is easy to deliver the data
to the particular network, from there it use L2 address to deliver to the
particulatr host( I mean with in the network).

Usually Routers are used to route the packets bet ween the networks.