Prior to the introduction and use of the OSI Network model, most computer networks were

monolithic. Which of the following were features of an older monolithic network solution?

a$.$ Everything needed to use a network had to be purchased from a single company. This

includes the network applications, networking software, and network hardware.

b$.$ It was simple to connect networks using one vendor$$s system to other networks, even if

the other networks were running a different vendor$$s network system.

c$.$ Transferring data between different vendor networks was extremely difficult.

d$.$ Monolithic networks made it very simple to create the Internet.