| Jeremiah DeWitt Weiner 2004-10-27, 5:52 pm |
| Jeff <zhefu.fan@gmail.com> wrote:
> What attribute of Internet Protocol is exploited by tools like
> traceroute to determine packet routing?
Firstly, your subject doesn't seem to have anything to do with
your question.
Traceroute intentionally sets the TTL field so that the packet
will expire at some hop on the way. When this happens, the host/device
where the packet expired will send an ICMP message saying that the packet
expired. Traceroute ups the TTL by one every time so it can see where a
packet with TTL of 1 expires, where one with a TTL of 2 expires, and so
forth, until it reaches the host you specified. The traceroute man page
explains this reasonably well. If you want to know more about the IP
packet structure, googling for "IP packet structure" is a good start.
JDW
|