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. >=20 > Background: >=20 > - my internet access is five wireless and five wired hops downstream > from a 1/2 T1 (ten Buffalo AirStation G54 routers in all). >=20 > - my connection has a lot of jitter--ping's usually vary from 10ms to > 150ms within a two second window >=20 > - FWIU, jitter is related to congestion >=20 > - I have setup a FreeBSD box to monitor [1] each router along the path > using smokeping. >=20 > 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): >=20 > |--------- Building 1 --------------| |--- Bldg 0 --... >=20 > +-----------+ +------------+ +-----------+ > | .203 | | .202 | | .201 | > | Router In |<- wire ->| Router Out |<- wireless ->| Router In | > +-----------+ +------------+ +-----------+ >=20 > avg RTT: 7.3ms 12.1ms 7.8ms >=20 > % lost: 2.37% 14.25% 2.64% >=20 > max RTT: 20ms 80ms 13ms >=20 >=20 > My FreeBSD box is a four more wireless hops to the left of .203. >=20 > A slew of questions ... >=20 > What is going on here? >=20 > 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. >=20 > Over the past 13 hours, the averages are consistent with the three-hour > averages, while the Max RTT discrepancies are even higher: >=20 > .203 / .202 / .201 =3D 20ms / 145ms / 13ms. >=20 > Is .202 congested? >=20 > Is the .202 router "bad"? >=20 > How can I debug this further? SNMP? >=20 > If SNMP, what values should I track/inspect? > - # of packets with errors? > - # of queued packets? > - ?? >=20 > Thanks for any pointers, >=20 > m >=20 > [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. :) >=20 > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.o= rg" >
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