RE: level3.net in Chicago - high packet loss?!? - Test

6 Sep 2005

      Stef,
...
-----Original Message-----
From: Network Fortius [mailto:netfortius@gmail.com] 
Sent: Tuesday, September 06, 2005 10:25 AM
To: nanog@merit.edu
Subject: Re: level3.net in Chicago - high packet loss?!?
And how exactly would you interpret the number returned by net_loss  
(int), in a column called "LOSS", in reference to reachability of a  
"hop" between two end points:
int net_loss(int at)
{
   if ((host[at].xmit - host[at].transit) == 0)
     return 0;
   /* times extra 1000 */
   return 1000*(100 - (100.0 * host[at].returned / (host[at].xmit -  
host[at].transit)) );
} ?
This piece of code is modified by me (all mistake is mine).  It 
converts the the drop to percentage.  x 1000 was a trick to handle
none int returned by the function.  This was an issue I did not 
have a clear answer.

Regarding to you original post.  Your trace end2end (last hop) has 
0.0% drop proved the entire path was free of packet loss.  The drop 
in the middle of the path could be related to ICMP rate limit or 
other things.  Should it was a congestion in the X hop, every hop 
after X would be impacted by it.  Thus X+1, X=2... has to be > 0.0%.

Hope this help,

Min
...
Thanks,
Stef
Network Fortius, LLC
On Sep 6, 2005, at 7:45 AM, Robert E.Seastrom wrote:
...
Network Fortius <netfortius@gmail.com> writes:
...
Anybody having any idea why such a high packet loss on lever3's
network, in Chicago?
End-user misinterpreting output from MTR.  This network does not
appear to have any packet loss end-to-end.
---Rob
...
Stef:~ scm$ mtr -r www.yahoo.com
...
tbr1-p010802.cgcil.ip.att.net             0%    16   16   15.12
24.21   49.26
ggr2-p310.cgcil.ip.att.net                0%    16   16   13.18
42.66  118.99
so-1-1-0.edge1.chicago1.level3.net        0%    16   16   14.48
35.84  126.48
so-2-1-0.bbr1.chicago1.level3.net        63%     6   16   14.44
43.74   79.97
...
...
^^^^^^^
as-1-0.bbr2.sanjose1.level3.net           0%    16   16   61.95
80.64  176.01
ge-10-2.ipcolo3.sanjose1.level3.net       0%    16   16   63.37
95.61  148.46
unknown.level3.net                        0%    16   16   63.34
86.46  168.62
unknown-66-218-82-217.yahoo.com           0%    16   16   62.09
88.91  127.58
p4.www.scd.yahoo.com                      0%    16   16   64.51
89.96  183.79
TIA,
Stef
Network Fortius, LLC

RE: level3.net in Chicago - high packet loss?!?

Min Qiu

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