gatebook CN 2

Question

A router is emitting out IP packets whose total length (data plus header) is 
1024 bytes.Assuming that packets live for 10 sec, what is the maximum line 
speed the router can operate at without danger of cycling through the 
IP datagram identification number space?
A. 53.6 Mbps
B. 3.5 Tbps
C. 5.36 Mbps
D. 35 Tbps

Comments

what is the answer?

Answer 1

The IP datagram Identification number space is $2^{16}-1$ = $65535 $
Packet lifetime = 10 seconds

Therefore, a maximum of 65535 packets may be sent in 10 seconds.

If any more packets were to be sent within the 10 seconds, there would be multiple live packets with the same ID.
$\left \lfloor \frac{65535}{10} \right \rfloor$= $6553$ packets/sec

The maximum line speed @ 1024 bytes/packet is:
$1024\ bytes/packet \times 6553 packets/sec \times 8 bits/byte = 53,682,176 bps (~ 53.6 Mbps) $