Date: Thu, 7 Jul 2005 10:23:11 -0400 From: Mark Bucciarelli <mark@gaiahost.coop> To: questions@freebsd.org Subject: Network Debugging Message-ID: <20050707142311.GL2792@rabbit>
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I'm trying to improve the performance of our rural homebrew wireless
broadband and am hoping some of the folks here can give me a pointer or
two as to what network monitoring tools I should use.
Background:
- my internet access is five wireless and five wired hops downstream
from a 1/2 T1 (ten Buffalo AirStation G54 routers in all).
- my connection has a lot of jitter--ping's usually vary from 10ms to
150ms within a two second window
- FWIU, jitter is related to congestion
- I have setup a FreeBSD box to monitor [1] each router along the path
using smokeping.
The smokeping charts are showing me some interesting stuff. Here is
some data from the past three hours (I am using the smokeping default of
20 pings sent every five minutes):
|--------- Building 1 --------------| |--- Bldg 0 --...
+-----------+ +------------+ +-----------+
| .203 | | .202 | | .201 |
| Router In |<- wire ->| Router Out |<- wireless ->| Router In |
+-----------+ +------------+ +-----------+
avg RTT: 7.3ms 12.1ms 7.8ms
% lost: 2.37% 14.25% 2.64%
max RTT: 20ms 80ms 13ms
My FreeBSD box is a four more wireless hops to the left of .203.
A slew of questions ...
What is going on here?
I am confused by the max RTT readings and packet loss stats for .202 and
.201. How can a router further away from me have better performance?
Over the past 13 hours, the averages are consistent with the three-hour
averages, while the Max RTT discrepancies are even higher:
.203 / .202 / .201 = 20ms / 145ms / 13ms.
Is .202 congested?
Is the .202 router "bad"?
How can I debug this further? SNMP?
If SNMP, what values should I track/inspect?
- # of packets with errors?
- # of queued packets?
- ??
Thanks for any pointers,
m
[1] Pentium II 350MHz with 4 Gb drive, underclocked to 100MHz so I can
turn off the power supply fan and make it real quiet. :)
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