Very slow Gb connection

kwiqsilver · Guru Joined: 19 Mar 2003 Posts: 360

I just set up a gigabit connection using a Marvell 88E8001 (sk98lin module) and a RTL-8169 (r8169 module). I had it running with a cat-5 crossover cable, but was only getting about 150Mb/s. I then bought a cat-6 crossover and now it's only running about 120Mb/s.
Is there a way to test the two ethernet controllers to see which one is running slow, or if it's the cable? But a cat-6 cable should support those cards at full speed, right?

NeddySeagoon · Posted: Tue May 17, 2005 7:32 pm Post subject:

kwiqsilver,

A 32 bit 33MHz PCI bus cannot provide data fast enough to max out a 1Gb link.
If its shared with other devices the data rate available for the NIC is reduced further.
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nobspangle · Posted: Tue May 17, 2005 8:07 pm Post subject:

Also bear in mind that most hard disks aren't going to be able to sustain anyware near 1Gb/s

kwiqsilver · Guru Joined: 19 Mar 2003 Posts: 360

That's true. But the hard disks on both ends are capable of 50MB/s+ sustained transfer, so if the network was capable of that, a remote harddisk would be almost as fast to access as a local one. That's basically what I'm going for.
But in any case, a gigabit connection should be able to outperform 10MB/s, which is more along the lines of a decent 100Mbps connection.

NeddySeagoon · Posted: Tue May 17, 2005 9:13 pm Post subject:

kwiqsilver,

kwiqsilver · Guru Joined: 19 Mar 2003 Posts: 360

The network line is most likely the bottleneck. A 32-bit 66MHz PCI bus can transfer 2112Gbps (theoretically).
The video is all on the AGP bus for both systems. Neither system was running audio, significant network traffic, or making significant disk use.
The only things of significance running were the reading from (or writing to) the SATA bus, and the network connection between the boxes, which were using a small percentage of the capacity on the PCI bus, even with ACKs and such being returned.

But my original question remains: Is there a way to analyze a network card to verify what sort of throughput it is capable of? Years ago I had to run a 3Com utility to enable duplexing on my 3c905b card (it was set to not duplex out of the box), and I want to rule out something like that in this case.

encase · n00b Joined: 25 Oct 2004 Posts: 55 Location: Switzerland

150MByte/s * 8 = 1000Mbit/s

kwiqsilver · Guru Joined: 19 Mar 2003 Posts: 360

encase · n00b Joined: 25 Oct 2004 Posts: 55 Location: Switzerland

ok...

can you post all specifications of your hardware: wires, cards, routers, switches etc.
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kwiqsilver · Guru Joined: 19 Mar 2003 Posts: 360

Box One has an Asus A7N8X-E Deluxe motherboard with onboard Gigabit Ethernet:

yottabit · Posted: Sun Jun 12, 2005 10:22 pm Post subject:

also turn on jumbo frame support... you can do this in Linux simply by setting the MTU to 9000 bytes instead of 1500 bytes (use the 'ifconfig' command, and for help 'man ifconfig'). Be sure to do this on both ends or there's no point.

If the other end is Windoze, it's usually a driver option in the driver properties through Device Manager.

(I mention Jumbo Frame because you're directly connected with crossover cable. If you're going through a switch, be sure the switch supports Jumbo Frame explicitly or you may have issues.)
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