Rick,
Here is a formula I found somewhere to get some idea of how well a WAN link
is performing. Problem with ethernet is the expected through-put is well
under 1 ms and ping tells you the response is <1ms ... not much help. You
might try pinging a box at your ISP from a box connected to the outside
network segment (not through you firewall). Then try to ping that same box
at your ISP from a box inside you firewall and check the difference. Not an
exact science though it might help.
<begin paste>
You ping from a PC (PC1-10.1.1.1) on one side of the WAN link to a PC
(PC2-10.2.1.1) on the other side using a 1024 byte packets. This will give
you a theoretical speed.
Ping from PC1 to PC2 with a 1024 byte packet (1016 data bytes + 8 bytes of
ICMP header = 1024)
1024 bytes * 8 bits per byte = 8192 bits
#ping -s 1016 10.2.1.1
With a line speed of 256,000 bits/second you can calculate the time it would
take to send a packet
from PC1 to PC2 as follows:
256000/8192 = .032 seconds or 32 ms
So in a perfect world it would take 32 milliseconds to send a single 1024
byte packet from PC1 to PC2.
Remember that the ping process sends one ICMP type 8 echo-request packet
from PC1 to PC2 and then PC2 sends
an ICMP type 0 echo-reply back to PC1 so we have to figure the round trip.
32 ms * 2 = 64 ms round trip
This formula assumes that the speed of light times the distance is equal to
zero.
The speed of electricity is equal to the speed of light given no resistance.
186,000 miles/second * distance = 0
Therefore, the above ping should indicate 64 ms ping response times in a
perfect world.
We all know we don't live in a perfect world and are bothered with things
that add to the latency like
the time that it takes for the routers to make a routing decision and
forward the packets between it's interfaces.
There could be other traffic going across the link that would also add to
the latency, but this gives you an idea
of what to expect.
<end paste>
Hope that helps
Rich
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Rick Lim
Sent: Friday, July 06, 2001 5:28 AM
To: firewalls@Lists. GNAC. NET
Subject: Iptables latency/delay
Does any one know how to figure out the amount of latency/delay
a packet would have that would have to transverse a RH7.1 iptables
NAT on a 266mhz pentium II?
I know this would depend upon the speed of the machine, but is there
a formula to predict this?
I have a friend that has asked this question.
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