A unit of information in the transport layer is called $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.[2]$

$2)$ The protocol used to transfer email messages between the sender$\text{'}$s mail server and the

recipient's mail server is $\_\_\_\_\_\_\_\_.[2]$

$3)$ SSL stands for $\_\_\_\_\_\_\_\_\_\_\_.[2]$

$4)$ Ethernet is a $\_\_\_\_$ layer protocol. $[2]$

a$)$ Physical Layer b$)$ Link Layer c$)$ Network Layer d$)$Transport Layer

$5)\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_$ servers are responsible for an organization's web servers and mail

servers.$[2]$

a$)$ Authoritative DNS servers b$)$ Top$-$level Domain servers c$)$ Root DNS servers