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Peer-to-peer throughput on LAN

Markbnj

Markbnj

Elite Member <br>Moderator Emeritus
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I was running into throughput issues moving a large tarball to a company server today, and as part of a series of tests I transfered some files between two machines here on my LAN, using FTP and SFTP/SCP.

Both machines are wired in to a DLink DI-514, have 10 megabit ethernet cards, and cable runs of six feet. One machine is a Windows XP SP2 system and the other is a Debian sid system.

Copying files between these via either FTP or SFTP maxes out at 350 kbps. There are four wireless clients on the network as well, but none of them are in active use at this time.

So it seems like I should get much better throughput than that. What do you guys think?
 
If they're 10 meg ethernet half-duplex cards that is about normal. Make sure the NICs are set to autodetect speed/duplex.

350 kbs is about 3.5 Mbs including overhead which is about right for 10 meg half-duplex ethernet.
 
Thanks, spidey. The windows box NIC is set to full autonegotiate, and on the Debian system the kern.log file says eth0 is running full-duplex. I'm beginning to wonder whether the router is an issue.
 
They're standard six-foot patch cables, factory terminated. Nothing fancy, but I didn't think I needed to worry too much about the quality at 10 meg.
 
Originally posted by: Markbnj
Thanks, spidey. The windows box NIC is set to full autonegotiate, and on the Debian system the kern.log file says eth0 is running full-duplex. I'm beginning to wonder whether the router is an issue.
Click to expand...

Well you could have a duplex mismatch. This is where one end of the link is operating full duplex and the other half. That can cause really poor performance.
 
Thanks for those links, Jack. As far as I can see I am getting just about exactly half what I should be. I checked all the NICs and again as far as I can tell they are all in full-duplex mode. The stack is optimized on the windows box, but I will have to mess around with debian system to figure out how to do that. Nevertheless I wouldn't expect a 100% increase from whatever I do there.

I did see something interesting, don't know if it will be meaningful to you guys. If I am pulling a large file off the debian box I get no more than 350-ish kbps. If I push the file from the Windows xp box to the debian box I get twice that, or around 700-750 kbps.

Going to look a little bit at the router settings, but I don't recall there being much there that affects LAN throughput.

 
The Router per-se is Not a factor, the LAN uses only the switch part of the Router.

100Mb/sec cards cost only few $$$ may be it is the time to switch over to late 20th century (the 21st century is already Giga time).

Did you try to transfer between one of the Wireless computers and the XP, and between the same Wireless, and the Debian and compare the outcome.
 
Actually I didn't try wireless. I did see the anomaly with coming vs. going between the XP and debian machines. I get about twice the performance copying data to the debian machine as copying it from. Wierd.

The NICs on both computers report 100 mbps links. I need to check the switch on the DI-514 (you're right, switch not router). It's probably 2-3 years old at this point, would think it was 100 mbps too, which makes the throughput I'm getting all that much more surprising.
 
Switches and NICs aren't that complicated. Sounds like you have a duplex mismatch. Make sure both the NIC and switch are set to autonegotiate.

Number one cause of ethernet performance problems is cabling.
Number two is a duplex mismatch.
 
Thanks for the tips, guys. I don't see anything else I can mod on the settings for the NICs, and there is almost nothing I can do to the DLink with regards to switch operation. I agree that it sounds like a duplex mismatch. I suppose it could be bad cabling, but I'm inclined to think the standard patch cables I'm using are at least OK. Nevertheless I am going to upgrade the switch/router to something that supports gigabit and N, and take it from there. I will probably also upgrade the NICs in the two machines and replace the cables.
 
On one post you say you're using 10mb NIC's and on another post you're saying the speed is at 100mb? Which is it, are you using 10mb or 100mb NIC's. If you're using 10mb, it's worth the price just to upgrade them (at this point, Gig-E cards are like...$15 or $20)
 
Originally posted by: kevnich2
On one post you say you're using 10mb NIC's and on another post you're saying the speed is at 100mb? Which is it, are you using 10mb or 100mb NIC's. If you're using 10mb, it's worth the price just to upgrade them (at this point, Gig-E cards are like...$15 or $20)
Click to expand...

The first post was my mistake. When I looked at it more carefully I realized that both NICs are running 100 mbps links.

I decided to upgrade the router and one NIC. The NIC on the XP box is a Marvell integrated that should support gigabit, plus I bought one Intel NIC for the Debian system. For the router I went with the DLink DIR-655. I don't really need N, and I am not 100% certain this will solve the issues, but the backbone was due for an upgrade anyway.

Also bought two 7' CAT-6 550 Mhz CAT-6 patch cables.
 
I hate to go off on a tangent here, but I've dealt with a lot of Linux systems where the admin was ranting and raving and how much faster the network stack was than windows only to find it's real xfer speed was absurdly bad while the windows machines chugged along with no problem. SMB negotiation problems in general can be a nightmare to troubleshoot, but FTP should be more bulletproof and should flat out make those NIC cards scream 'mommy'.

Yeah, I've heard the claims that 'all Inel NICs work great with Linux'....pull my finger. Debian is kind of a black art and isn't exactly Ubunto....just something to think about.

I would be extremely curious what would happen if the following tests were made:

-Force both NICs to 100/half just to see what happens.
-Throw another Windows box on that same switch and do some file copies and test the speed.
 
No tangent at all, as far as I am concerned. I'm maybe a little apprehensive about getting the Intel NIC to work on Debian... we'll see 🙂. Can't lose more than $25 on that gamble. They do have Linux drivers available for it on their website.

Thing is, from the Windows box to Debian I get 700+ kbps, and almost exactly half that going the other way. You're right, I should toss another Windows box on the switch and try it out. Might do that tonight.

Beyond that I'm sort of out of ideas. I know enough Linux to get the config and ifup/down the ethernet interfaces, but I don't have the low-level chops there that I do on Windows. Both machines _say_ the NICs are at full-duplex 100 mbps. If that's true, then it pretty much leaves the switch in terms of hardware to look at. Of course, there could be something in software hobbling the Debian box. It's running bind9 and squid and serves all our machines here as a caching proxy/DNS, so I'd like to have it work as well as possible.
 
I'd really, really like to see what happens with two Windows boxes chatting at each other just to rule out software problems with Debian. As much as I'm trying to gain more respect for Linux, I've simply had too many performance problems with light weight Linux utility distros compared to even sloppy Windows 2000 installs on the same hardware. Debian can bring new life to a 486 based spare PC, but when it comes to newer hardware things are different.

The Windows box pulling files down from the Debian box with FTP should flat out saturate the NIC.

This is why I keep 3Com 3c980's in my bag at all times for diagnosing network problems. The drivers are included with every version of windows worth using, and the 3C980 negotiates with anything. I otherwise haven't had to mess with duplex settings in my own environments in a very long time. Oddly, Intel is the worst offender with this because their auto windows updates can do screwy things to their 10/100 server based NICs. Can't tell you how many times I've had to drive across town because an Intel NIC update cut off a production server because of a stupid media setting. This is where Linux has the advantage.
 
But even pulling data to the XP machine from Debian I am only getting .7 mBps or so, which if the links are really at 100 mbps is quite a difference. I checked the specs on the older DLink DI-514 I am using, and it should support 10/100 at the switch ports. So at this point I am not sure what's going on.

At least putting the DIR-655 in with new high-quality cables should remove any doubts about the switch/transport. If the Intel NIC won't work in the Debian system I will still be in a position where I should be getting 100 mbps links. If the throughput doesn't improve I will have to dig into the Debian system more than I have so far.
 
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