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i have one doubt , as we know ip address has given to every device which has been connected to internet as well as ip is unique then why we using data link address for forwarding we can use ip address for forwarding(doing by router) and completely eliminate the data  link layer.

why we need one extra layer (data link layer) as forwarding of packet also done by router.
asked in Computer Networks by Active (2.8k points) | 18 views

Data link layer deals with more hardware part of the network. It performs tasks such as Collision detection and collision avoidance which is out of scope of network layer. Network layer is the most important layer which keeps internet intact but it cannot do the tasks which link layer can do and vice versa. Now the question comes to your mind that why these 2 layers can't be merged? These two layers are almost working together for example, while fragmentation network layer will not know the MTU if there is no DLL, DLL is responsible from where Network layer gets the MTU and do the fragmentation, and the final point of yours that router is responsible for routing the packets on the internet yep that's true, but its not routers job to get the data from your device. It is layer 2 devices such as a switch, its job of a switch to connect a device to a network. When you are buying a  router you are not just buying a router but also it contains a switch which is  responsible for data to transfer from your Ethernet port to router's Ethernet port. 

1 Answer

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IP address can be unique in Internet but if we have various subnets in a single network then two same ips can be assigned in two different subnets.Network layer does not play with the Mac address of the host, so eliminating data link layer will cause ambiguity.So as to connect to a service we need a socket that is specifically a combination of ip and mac and mac can only be know at Data link layer not at Network Layer.



P.S-Correct me if i am wrong ty.
answered by (135 points)

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