In the stop$-$and$-$wait protocol, the frame size is decreased. In this

case the efficiency will:

$($a$)$ decrease $($b$)$ increase $($c$)$ double $($d$)$ not be affected

$3\mathrm{.}4($a$)$

$($b$)$

$($c$)$

$($d$)$

$4)$ In PC$/$IP$,$ host$-$to$-$host communication is handled by the following

layer:

$($a$)$ transport layer $($b$)$ internet layer $($c$)$ link layer

application layer

$($d$)$

$4\mathrm{.}1$

$($a$)$

$($b$)$

$($c$)$

$($d$)$

In the ISO$/$OSI model, errors are corrected in the following layers:

$($a$)$ application and network layers $($b$)$ transport and data link

layers $($c$)$ data link and network layers

$($d$)$ transport and

network layers

$4\mathrm{.}2($a$)$

$($b$)$

$($c$)$

$($d$)$

$5)$ Two communication nodes use the Go$-$Back$-$N ARQ protocol

with a window size of $500.$ Frames $1$ to $500$ are sent, but frame $500$

is received in error. In this case the transmitter needs to:

$($a$)$ retransmit frame $500$ only $($b$)$ retransmit frame $1$ and all

subsequent frames $($c$)$ retransmit frames $1$ to $500($d$)$ neither a$,$ b

or C$.$

$5$

$($a$)$

$($b

$($C$)$

$($d$)$