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TOPIC: ICMP Time Out + TTL

ICMP Time Out + TTL 12 years 8 months ago #3242

  • Cheetah
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Hi


As usual, I am going thru different papers of Chris & Team in the site. Just a question here on this paper below: www.firewall.cx/ip_routing.php , on the following section.

"This is also one of the reasons why sometimes the first "ping" will timeout. Because it takes some time for an ARP to be sent and the requested machine to respond with its MAC address, by the time all that happens, the TTL (Time To Live) of the first ping packet has expired, so it times out!"

TTL expired, and timing out; is it different or same? I believe it is different. Normally 'TTL expired' happens after the router(s) decrements the TTL value and it reaches '0' and has still not reached the destination host.

But... If its different how does it time out :-)

Please correct me, if I am wrong.

Regards
Cheetah
Kind Regards,
<b>Cheetah</b>
<i>The outcome of devotion is, quality!</i>
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Re: ICMP Time Out + TTL 12 years 8 months ago #3244

  • tfs
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TTL is time to live. This is also a hop count in Traceroute. It is a countdown timer that each router it hits decrements by one. When it hits zero it, the router sends an ICMP packet back with the "time exceeded" flag set (type 11).

Ping uses a timer (normally 1 second). If that time is exceeded, it is timed out.
Thanks,

Tom
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Re: ICMP Time Out + TTL 12 years 8 months ago #3245

  • sahirh
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yep there is a difference, that looks like we should make it 'times out' to make it more clear
Sahir Hidayatullah.
Firewall.cx Staff - Associate Editor & Security Advisor
tftfotw.blogspot.com
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Re: ICMP Time Out + TTL 12 years 8 months ago #3246

  • Cheetah
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Hi Team,

Thanks.

Regards
Cheetah
Kind Regards,
<b>Cheetah</b>
<i>The outcome of devotion is, quality!</i>
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