Re: whence "ping -w"?
On Thu, 02 Nov 2000 22:31:47 PST, Francois Gouget writes:
> IIRC, most ping implementations send an 8 byte timestamp obtained
>with gettimeofday as the payload of their ICMP echo request packets.
>This payload is copied in the ICMP echo reply packets. So wwhen ping
>receives an ICMP echo reply message that is addressed to itself
>(matching icmp id), it just does another call to gettimeofday, substract
>the timestamp that was returned, and print the RTT.
> This way ping does not need to keep track of all the packets it sent
>and thus does not need a timeout. It can even handle packets that come
>back out of order.
yep, but most ping implementations ignore packets coming in after a
given time, most of the time you need to do a ping -v to see them
(requires root privileges on some machines because it wants to put the
interface in promiscous mode where applicable).
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