$($a$)$ A transport$-$layer protocol, like a network$-$layer protocol can provide two types of services: connectionless and connection$-$oriented. Compare these two services with the help of appropriate diagram$($s$).$

$[6$ marks$]$

$($b$)$ Design the simplest possible transport$-$layer protocol that will get application data to the desired process at the destination host. Assume operating system in destination host assigned a $4-$byte port number to each running application process. $($Hint: The network layer in the source host accepts a segment of maximum size $1200$ bytes and destination host address from the transport layer.$)$

$[4$ marks$]$