$2\mathrm{.}3$ Task $1\mathrm{.}3$: Traceroute

The objective of this task is to use Scapy to estimate the distance, in terms of number of routers, between

your VM and a selected destination. This is basically what is implemented by the traceroute tool. In

this task, we will write our own tool. The idea is quite straightforward: just send an packet $($any type$)$ to the

destination, with its Time$-$To$-$Live $($ITL$)$ field set to $1$ first. This packet will be dropped by the first router,

which will send us an ICMP error message, telling us that the time$-$to$-$live has exceeded. That is how we get

the IP address of the first router. We then increase our TTL field to $2,$ send out another packet, and get the

IP address of the second router. We will repeat this procedure until our packet finally reach the destination.

It should be noted that this experiment only gets an estimated result, because in theory, not all these packets

take the same route $($but in practice, they may within a short period of time$).$ The code in the following

shows one round in the procedure.

$a-IP()$

a$.$dst$.=,1,2,{3\mathrm{.}4}^{\text{'}}$

a$.$ L$.$t$.1-3$

b $-$ ICMP $()$

send $(\frac{a}{b})$

If you are an experienced Python programmer, you can write your tool to perform the entire procedure

automatically. If you are new to Python programming, you can do it by manually changing the 'TIL field in

each round, and record the IP address based on your observation from Wireshark. Either way is acceptable,

as long as you get the result.