1) What is a Software Defined Network and how does it differ from a traditional (non-SDN) network? What are 3 advantages of an SDN? 2) We know that end to end error management is handled by TCP at the...

1) What is a Software Defined Network and how does it differ from a traditional (non-SDN) network?  What are 3 advantages of an SDN?

2) We know that end to end error management is handled by TCP at the transport layer.  So theoretically it is not necessary to implement error detection/correction at the link layer – yet it is implemented there.  Why is it beneficial to implement error detection/correction at the link layer as well as the transport layer?