OSI Model

Question

Network layer is used when data is to be delivered across network. So, for delivering within a network, there is no need for network layer (Ref: Pg-49, Computer Networks, Forouzan, 2 Edition). So in that case will Transport layer directly communicate with Data Link layer ? Or will Network layer be in picture, but do nothing other than simply passing data to Transport layer ?

Comments

You meant in a LAN?

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yes I meant that

Answer 1

ACTUALLY without network layer we cant say that destination is present in our won network or in some other network so..

when message reach network layer first of all it is checked by using default subnet mask of host...hence if destination is present in same network then it is directly sent to destination otherwise sent to default gateway.

Answer 2

Network layer is the glue due which all the networked application can communicate within a given network or internet it is essentially the backbone of internet so it is required for reliable end to end delivery and all of the networked applications need it , also the network layered provides services to the application layered and well the link layer , OSI is one of the theoretical model , The four layered (Application,Transport,Network,Link) is the one commonly used by all applications and network layer is the most important layer for this . Here is the link which can help in understanding this better (https://www.youtube.com/watch?v=_BC5ALTJDXo&index=3&list=PLegVVnqIQKAaGYvbwi6hy5tCdQt64nN_M)