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Date:      Mon, 9 Aug 2004 17:35:45 +0400
From:      "Nickolay A. Kritsky" <nkritsky@star-sw.com>
To:        sirola@fisica.unige.it
Cc:        freebsd-net@freebsd.org
Subject:   Re: retransmissions with bge driver?
Message-ID:  <78135817453.20040809173545@star-sw.com>
In-Reply-To: <878ycoag8v.fsf@statpro.com>
References:  <878ycoag8v.fsf@statpro.com>

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Hello sirola,

Try to switch one of the NICs to half-duplex mode. This should do the
trick.

Monday, August 09, 2004, 12:05:20 PM, sirola@fisica.unige.it wrote:

sfui> Hello,
sfui> I'm going to set up a server with FreeBSD 4.10. While testing the
sfui> network performance, I see a lot of tcp retransmissions on both the
sfui> network cards this server have. These are identified as BCM5704C and
sfui> using the bge driver. Actually, the network cards are configured as
sfui> 100baseTX <full-duplex> (no autoselection) and i get a 5% of
sfui> retransmissions. Modifying the tcp kernel configuration as follows
sfui> raises the maximum transfer rates a bit, from 70KBytes/s to
sfui> 150KBytes/s which are nevertheless poor performances. The relevant
sfui> parts of my net.inet.tcp are as follows:

sfui> net.inet.tcp.inflight_enable: 1
sfui> net.inet.tcp.sendspace: 65535
sfui> net.inet.tcp.recvspace: 65535
sfui> net.inet.tcp.rexmit_min: 20
sfui> net.inet.tcp.rexmit_slop: 200
sfui> kern.ipc.nmbclusters: 32768

sfui> By the way, no errors/collisions are reported with netstat -in...
sfui> netstat -s shows

sfui> tcp:
sfui>         3283167 packets sent
sfui>                 1934388 data packets (438813217 bytes)
sfui>                 20514 data packets (28327158 bytes) retransmitted
sfui>         2095620 packets received
sfui>                 1786464 acks (for 438791442 bytes)
sfui>                 22570 duplicate acks

sfui> what could be the reason of all these retransmissions? Bad cabling? A
sfui> poor switch?

sfui> Thanks in advance for your help,
sfui> enrico

sfui> P.S.
sfui> If I'm writing to the wrong list, please let me know it

-- 
Best regards,
;  Nickolay A. Kritsky
; SysAdmin STAR Software LLC
; mailto:nkritsky@star-sw.com




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