$($a$)$ Which protocol $-$ Go$-$Back$-$N or Selective$-$Repeat $-$ makes more efficient use of network

bandwidth? Why?

$(1$ Marks$)$

$($b$)$ Consider a reliable data transfer protocol that uses only negative acknowledgements.

Suppose the sender sends data only infrequently.

$($i$)$ Would a NAK$-$only protocol be preferable to a protocol that uses ACKs? Why?

$(1$ Marks$)$

$($ii$)$ Now suppose the sender has a lot of data to send and the end$-$to$-$end connection

experiences few losses. In this second case, would a NAK$-$only protocol be preferable

to a protocol that uses ACKs? Why?

$(2$ Marks$)$

$($c$)$ Table $1$ below illustrates the three types of the Internet Control Message Protocols

$($ICMPs$).$ For each ICMP type given in Table $1,$ state the:

$($i$)$ Description

$(3$ marks$)$

$($ii$)$ Reason for Sending

$(3$ marks$)$

Table $1$: Types of the ICMP Message