Date: Wed, 29 Mar 2006 20:35:04 -0500 From: "Ashish Awasthi" <awasthi.ashish@gmail.com> To: freebsd-pf@freebsd.org Cc: lu ping <luping.nju@gmail.com> Subject: Packet drops and queue length upon bandwidth limiting in PF Message-ID: <5289d17a0603291735u194807cbu853b438edc80049b@mail.gmail.com>
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Hi friends, I am a relative newbie, so please don't flame me if my question doesn't mak= e sense. In a network experiment to determine appropriate length of router buffers, = I am using pfctl on FreeBSD 5.3 to limit the bandwidth to 100 Mbps on a 1 Gig link and limit the queue to 240 packets, and I use iperf for sending out data. Connection is maintained between two routers running FreeBSD 5.3, connected by a 1 Gig link. I monitor on sender the pfctl and iperf statisitcs. As I see the iperf throughput go down from 94 Mbps to 50 Mbps and then rise again in accordance with the classic sawtooth curve of TCP, it is clear tha= t there must have been a packet drop, but "pfctl -s -queue -v -v" at the sender shows 0 losses and 0 drops. Moreover, the queue length as reported never overflows. Even netstat shows 0 retransmissions! I tried this with queue lengths of 50, 100, 240, 10 and 5. Only when queue length is on the order of 5 or 10 do I see packet drops in pfctl report (an= d also retransmissions in the netstat report); however, since I have limited the bandwidth and the outgoing traffic is shaped by this limitation, it is clear that there must be some packet losses in other cases as well. So, I tend to think that some other queueing is occuring apart from the ALTQ, and drops are occuring there. If so, how can I obtain those statistics? Thanks a lot for your help! Ashish
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