Date: Thu, 7 Jul 2005 12:13:56 -0400 From: Hornet <hornetmadness@gmail.com> To: questions@freebsd.org Subject: Re: Network Debugging Message-ID: <f42935a605070709135aaa814b@mail.gmail.com> In-Reply-To: <20050707142311.GL2792@rabbit> References: <20050707142311.GL2792@rabbit>
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On 7/7/05, Mark Bucciarelli <mark@gaiahost.coop> wrote: > 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? Most routers put a lower priority on ICMP, If the middle router has a higher load on it (which by your diagram it should), then the B router would be slower to respond to ICMP. Try using MTR (Matt's traceroute) It will give your real time stats on your network hack. > > 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. :) > > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >help
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