Both of these questions deal with the Transport layer 1 Why

Both of these questions deal with the Transport layer

1) Why DISCONNECT is necessary in simple transport service?

and from that,

2) When the client requests DISCONNECT, does the connection end abruptly?

Solution

1) DISCONNECT in a simple transport services is important because it is a primitive used for terminating the connection. After this no message can be sent.

2) When the client sends DISCONNECT then the server also sends the DISCONNECT packet to inform the client. When the server package is received by client then the process is ended.