retransmissions with bge driver?

[Nickolay A. Kritsky]

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 at 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 at star-sw.com