[ECOS] ethernet performance <TCPIP guru question>

[Stephen Polkowski]

Hello,

	I've been working on a simple ftp server for ECOS.  I have it up
and working on the intel pc using the 82559 ethernet card.  I'm also 
using redboot to load my application over the ethernet.

	When I ftp a file to my server application I seeing some really
slow ethernet speeds.  I have a 100Mb ethernet running on a 2Ghz Pentium 
  IV.  So, my system should be fast enough to handle the data.  I'm 
getting about 65k bytes a second transfer rate.  I should be get getting 
something close to 10M bytes a second.  What's the problem?

         I did a tcpdump from my Linux machine.  I've noticed two things.
First, the TCP window size in ECOS isn't sliding during the transfer. 
This might be confusing the sender, I'm not sure.  Also, I see a burst 
of data packets and ACKS from ECOS which appear good.  Then all of a 
sudden, ECOS starts to ACK to the same packet over and over.  After a
few more acks, the sequence resumes.  Is this normal?  Does this explain 
the slow network performance?

Here's the dump of the burst sequence running into the ACK sequence.

Thanks.

1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1507369:1508817(1448) ack 1 win 5792
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1508817:1510265(1448) ack 1 win 5792
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1510265:1511713(1448) ack 1 win 5792
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1511713:1513161(1448) ack 1 win 5792
1.1.1.2.55961 > 1.1.1.3.ftp-data: P 1513161:1514609(1448) ack 1 win 5792
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1513161 win 18824
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1514609:1516057(1448) ack 1 win 5792
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1516057:1517505(1448) ack 1 win 5792
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1517505:1518953(1448) ack 1 win 5792
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1518953:1520401(1448) ack 1 win 5792
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1513161 win 18824
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1520401:1521849(1448) ack 1 win 5792
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1513161 win 18824
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1521849:1523297(1448) ack 1 win 5792
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1513161 win 18824
1.1.1.2.55961 > 1.1.1.3.ftp-data: P 1513161:1514609(1448) ack 1 win 5792
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1513161 win 18824
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1513161 win 18824
1.1.1.2.55961 > 1.1.1.3.ftp-data: . 1523297:1524745(1448) ack 1 win 5792
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1513161 win 18824
1.1.1.3.ftp-data > 1.1.1.2.55961: . ack 1523297 win 8688

-- 
Stephen Polkowski
Centaur Technology
Austin, TX
(512) 418-5730


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