If the data link layer didn't exist, what changes would be required of a network layer protocol such as Internet Protocol (IP)?

What will be an ideal response?

Without a data link layer, IP or other network layer protocols would need to make provisions
for connecting every type of media that could exist along a delivery path. Moreover, IP
would need to change every time a new network technology or medium were developed. This
disadvantage is avoided by using a layered model for networking and by giving the data link
layer the job of placing data on a medium and controlling access to the medium.