Re: [ECOS] ethernet performance <TCPIP guru question>

[Gary Thomas <gthomas at redhat dot com>]

On Wed, 2002-04-24 at 18:35, Stephen Polkowski wrote:
> 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've tested TCP operations with eCos, using 100Mb interfaces, and I get
transfer rates of around 8Mbytes/sec (Linux host, sending data to an 
eCos application which simply sinks the data).

>          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.
> 

Which IP address is the eCos side?
I assume from your description that the eCos "server" program is being
sent the data.  What does it do with it when it arrives?

> 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



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