Question : TTL in IP Packet

I have a question about TTL.

May I know what is the different between
a) -i option for ping command, which is TTL and
b) TTL value from the ICMP echo reply packet?

Other than that, I ping a website, e.g. www.chula.ac.th with "-i 13" i get the result and show me the reply from a router but the TTL expired in transit. if i increase the value of TTL up to 15, i able to get the ICMP echo reply packet with TTL value but if i use tracert command to trace the path, after 12th hops it returns me 3 '*'s until the maximum no of hops, which is 30. Why the tracert never show me the result for 13th-15th hops?

Answer : TTL in IP Packet

The -i option is setting the maximum time to live for the packet. Normally that is 255. If you set it to 13 and it is more then 13 hops away, then the router that is the 13th hop will send you an expired in transit message to let you know that it could not forward the packet due to the TTL expiration.