scp copy speed

I have a linux computer and a windows computer.  Both have 100Mbps network cards and both are configured to be 100Mbps.  When I copy files I get a speed of about 2.0 MB / s.  Is this normal?  To me it seems a little slow for a 100Mbps network card.
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Are you using a switch or a hub?  Full Duplex connections?

How is the network being routed?

Are the CPUs fast enough to encrypt at line speed?  How heavily loaded are they?

In short, there are a number of variables that could impair performance.  You need to quantify them and then vary them until you get the desired level of performance.
bryanlloydharrisAuthor Commented:
Each one is connected to a switch.  It is a Netgear fast ethernet switch.  The model number is fs105.

Windows -> Network Connections -> Local Area Connection -> Speed = 100.0 Mbps
Windows = 2.4Ghz computer(has the dual core thing) seems very fast

Linux -> mii-tool = eth0: negotiated 100baseTx-FD, link ok
Linux = 1.6Ghz computer I'm not sure if this is fast enough

How can I tell if they are Full Duplex?

How can I tell how the network is routed?

There are 5 plugs on the netgear switch, here is what they are plugged into.

1. airport repeater(with a lan cable) -> main airport in other room -> to cable modem -> internet
2. windows computer with a lan cable
3. linux computer with a lan cable

>> How can I tell if they are Full Duplex?

They are, "FD" in "100baseTx-FD" stands for full duplex

>> How can I tell how the network is routed?

Easily ;) It's not since they both are plugged into one cheap fs105 switch. ;))

Really a mystery - how fast does a regular FTP between the two work?
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Well, clearly the Linux NIC is running full duplex, it's not so clear about the Windows one.

From Local Area Connection Properties, click on the Configure button, go to the Advanced tab and have a look at the Link Speed & Duplex property, if it exists.  It is most likely to be set to auto detect, but can be set to 100Mbs/Full Duplex.

From the Windows Command Prompt, enter the following:

route print

At the Linux command line, enter:


I suspect a lot of traffic is being routed via the wireless network, impacting SCP performance severely.  The way to fix that, if that is the case is to have a lan cable connecting the switch and the main airport which I presume is acting as the router/gateway for this network.

1st of all, Half/Duplex would not slow down things that much. In fact, with some switches it would even HELP.

2nd, he indicated that both computers are plugged into the same switch, and he never said anything about them having wireless cards - so how would the airport be involved? Even if it IS the gateway, these 2 computers would talk to each other directly, provided they are on the same subnet. And even if they weren't, the whole thing would only be limited to the speed between the switch and WAP, which most likely is 100mb anyway.
Set both NIC's to auto. Setting the speed to a fixed setting doesn't help if the switch isn't managed and also set to the same setting as the NIC connected to that port.
bryanlloydharris, it's quite slow.
I have about 10MByte/s in 100 Mbit/s network.
Cheap D-Link switch was used (in my test). Copying was done from Solaris/SPARC 1.4Ghz to FreeBSD/Intel 2.4Ghz.
One single file 430MB was transfered in 42 seconds.

Probably you are transferring a lot small files. In that case SCP works slower then it would be one big file.

Also it may be Linux who slows down your transfer. To check this, run small test.
Try to transfer the same file from Linux to Linux itself via SCP (use your local IP). And do the same from Windows to itself.
In Linux you may transfer to /dev/null or to real path.
most likely it's the encryption algorithm which slows your connection down.
See my answer in http:Q_21696152.html and play around with the algorithm used for encryption.


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bryanlloydharrisAuthor Commented:
I have just noticed the speed is erratic.

If I use FileZilla (with sftp connection) I get only 600kB/s
If I use cygwin xterm along with scp.exe (also cygwin) it is about 2.0 MB/s

If I use the linux computer scp it goes _much_ faster at about 7.2MB/s

So I'm still not sure about why it is this way.
There is nothing erratic about this.

If you _constantly_ get only 600kB/s out of FileZilla you pretty much have your answer, XoF is right.
bryanlloydharris, first, try to change encription algorithm, as suggested.
Also try pscp.exe on Windows machine. You can find it here:
bryanlloydharrisAuthor Commented:
Yes XoF you're right.  Here is the new speed using scp.  It is now about 10MB/s which is a lot faster.

$ scp -1 -cblowfish 100MiB bryanh@
100MiB                                         74%   75MB  10.5MB/s

Thank you for all the help, I didn't think so many would answer.

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