I'm having many little problems with my gigabit network.

My hard drive reads at 85 MB/s, so why am I downloading from the ftp server at 68 MB/s? How could I diagnose what is eating those 17 MB/s?

Why does my windows machine have a slow 326 Mbit/s transmit speed compared with ubuntu's transmit speed of 763 Mbit/s when testing with iperf?

Why do I get slow samba speeds?

Windows is connected to Ubuntu with a 6 foot crossover cable. Both machines are fully updated.

windows xp3
motherboard: gigabit ga-965p-ds3
cpu: C2D E4400
hard drives: 250gb seagate, read = 85 MB/s
lan: marvel 8053 Gigabit LAN (onboard, PCI-E)

ubuntu 8.04 gateway
motherboard: Asus P5B-MX
cpu: C2D E2160
hard drive: 250gb seagate, read = 85 MB/s
lan: attansic® L1 PCI-E Gigabit LAN controller (onboard, PCI-E)


  • windows pc downloading from gateway: 763 Mbit/s = 95 MB/s
  • gateway downloading from windows pc: 326 Mbit/s = 41 MB/s


  • windows pc downloading from gateway: 544 Mbit/s = 68 MB/s


  • windows pc downloading from gateway: 194 MBit/s = 24 MB/s
  • gateway downloading from windows pc: 160 MBit/s = 20 MB/s


        netbios name = SHWICK_GATEWAY
        server string = SHWICK_GATEWAY
        interfaces = lo, eth1
        bind interfaces only = Yes
        map to guest = Bad User
        passdb backend = tdbsam
        syslog only = Yes
        os level = 65
        preferred master = Yes
        domain master = Yes
        dns proxy = No
        wins support = Yes
        invalid users = root

        path = /home/ftp/
        create mask = 0640
        directory mask = 0750
        guest only = Yes
        guest ok = Yes

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What category is the crossover cable
They both got gigabit cards?

Yes both onbaord gigabit cards. Crossover is CAT5.

So I found how to make samba faster, I removed "SO_RCVBUF=8192 SO_SNDBUF=8192" from socket options. I let the tcp stack set the buffer size automatically now. 8192 was too small for a gigabit lan.

But is there any way I can improve the ftp speeds? The problem is server side, as I tested a download on both windows and from an ubuntu livecd, and both times it was 68 MB/s.

You should really be using cat6 cable on a gigabit LAN
giabit cards dont need crossover cables anyway, a patch is fine

Well I give up I guess I'll settle for 68 MB/s ftp and 43 MB/s samba. lame.

I tried a bunch of tcp tweaking on my ubuntu gateway, stuff from articles like

# TCP gigabit tweaks
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216

net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216

Tried setting mtu to 9000, tried disabling tcp sack. Double checked cables were cat5e. (cat5e supports gigabit)

Booted ubuntu livecd on windows machine, iperf got 940 Mbit/s down. And I get 544 Mbit/s from ftp server.

Tried messing with nfs, looked like i was getting 62 MB/s down. Couldn't do proper tests b/c livecd boot kept running out of space.

Whatever. Getting that last 17 MB/s isn't worth it if it's this difficult.

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