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Consider a very large network $10000$ routers. Two host $A$ and $B$ connected with this network. Host $A$ sends a data to host $B$. and after some unit of time host $A$ receives $ICMP$ time exceed message for the samedata packet. The number of router that can be travelled by packet when message return back to A _____________

Why ans is $255+254$

Why not after going some distance some ICMP message generated? Say if $ICMP$ message generated in $9999th$ router, then where it give error of time exceed message?

@Gateasp2020 TTL value will be decremented by 1 at router, no doubt about that. Actually, I used this fact to prove my point that we can't have a functional model where 10000 routers are connected in a path like fashion(Kind of proof by contradiction). Don't get confused what you know is correct, read the whole thread again you'll get the idea of what I'm saying,

@Anuj Mishra

Cant it happen after TTL =0 and now icmp packets are thrown

icmp packets doesn't have a ttl in header so hence it will traverse all the rest 9745 routers and will reach back to original source

1 vote