Date: Mon, 15 Dec 2003 14:39:15 -0500 (EST) From: junfeng@ece.gatech.edu To: luigi@iet.unipi.it Cc: freebsd-ipfw@freebsd.org Subject: dummynet dropping TCP packets Message-ID: <64995.65.106.15.98.1071517155.squirrel@secure2.ece.gatech.edu>
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Hi! all, I am using dummynet to simulate a network-connection with 65ms propagation delay. Dummynet is installed on a workstation with two network-cards, and is configured as a bridge (no IP for these interfaces). One network-card is connected to a Video Server (IP:192.168.200.100), which sends out 2Mbps video stream. The other network card is connected to a video client (IP:192.168.200.50), which receives video packets and does ARQ if there are packet loss. The feedback message is TCP. We simulate random loss of video packet at server end. And use dummynet to control the propagation delay between server and client. Here are the commands I used to control dummynet HZ=1000 ipfw flush ipfw add pipe 100 ip from any to any ipfw pipe 100 config delay 65ms And I observed that some TCP packets are dropped when they are sent from client to server. And then the operating system needs to retransmit these lost TCP packets after TCP time out, which causes extra delay in ARQ. I ever tried to seperate TCP from UDP packets and I got same result. ipfw add pipe 100 TCP from any to any ipfw add pipe 200 not TCP from any to any ipfw pipe 100 config delay 65ms ipfw pipe 200 config delay 65ms Also, I tried to use the bi-direction pipes, but seems that all traffic going through dummynet is in-bound traffic, so there is no packet goes through second pipe (pipe 200). ipfw add pipe 100 ip from any to any in ipfw add pipe 200 ip from any to any out ipfw pipe 100 config delay 65ms ipfw pipe 200 config delay 65ms Is there any error in my configuration? Thanks! Junfeng
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