## Question: how does ping do it!!!

### Question: how does ping do it!!!

Hello!

Here's the output from a ping command done on a DGUX AViiON system:

admin-rrw(81)# ping -snc2 -i 1 1.1.1.40
PING 1.1.1.40 (1.1.1.40): 56 data bytes
64 bytes from 1.1.1.40: icmp_seq=0 ttl=59 time=7.812 ms
64 bytes from 1.1.1.40: icmp_seq=1 ttl=59 time=0 ms

--- 1.1.1.40 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0/3.906/7.812 ms

See it measuring 3.906 and 7.812 milliseconds!!

How does ping do that?

The smallest unit of time I can find for any time related system call is
10,000ms!

Any help with this, even guesses will be greatly appreciated!

Rusty

### Question: how does ping do it!!!

>Hello!

>Here's the output from a ping command done on a DGUX AViiON system:

>admin-rrw(81)# ping -snc2 -i 1 1.1.1.40
>PING 1.1.1.40 (1.1.1.40): 56 data bytes
>64 bytes from 1.1.1.40: icmp_seq=0 ttl=59 time=7.812 ms
>64 bytes from 1.1.1.40: icmp_seq=1 ttl=59 time=0 ms

>--- 1.1.1.40 ping statistics ---
>2 packets transmitted, 2 packets received, 0% packet loss
>round-trip min/avg/max = 0/3.906/7.812 ms

>See it measuring 3.906 and 7.812 milliseconds!!

>How does ping do that?

>The smallest unit of time I can find for any time related system call is
>10,000ms!

Not sure what you mean there, but certainly not 10,000 ms
(milliseconds).

Quote:>Any help with this, even guesses will be greatly appreciated!

Find a way to read up on the structures and funcitons in
/usr/include/sys/time.h, specifically getitimer() and
setitimer() and the related structures timeval and itimerval.

But then also consider that precision and accuracy are two
distinctly separate issues.  Just because a result is presented
to a precision of 1 microsecond does not mean it is accurate to
1 microsecond!  For example, the second packet listed above is
unlikely to have actually returned in 0 milliseconds, regardless
of what the mechanism to measure it might be.  Averaging that
with any number, even an accurate one, results in an error.  If
the other number is 7.812 ms, but was obtained from a register
that is updated only every 152 microseconds, then the results are
all very useful, but the precision presented does not represent
the accuracy.

Floyd

--

HI there,

In about march we should be getting a second PC in our house. I was
concidering trying to network the two machines. One of the machines
is going to be a DOS/Windows affair while the other one is hoping
to become a DOS and Linux setup. I have a few questions that I hope
that someone out there can answer. (The kind of network I'm concid-
ering is peer-to-peer, I think)

1) Using Novell Netware light on the DOS/Windows machine, could it
connect to the Linux machine using standard networking stuff? Would
I be able to have netware on my DOS partition of my Linux/DOS machine
so that when I boot it up using DOS I'm still connected?

2) If I were using the Linux front end for DOOM, could I still play
a multiplayer game across the network? Or would I have to go back to
DOS?

3) Just out of curiosity, could anyone give me info on cost. I've

Cabling (roughly)                               :20
----
Total                                           136

This is a rough estimate, if anyone can confirm or deny this value