LAN file copy anomaly

  • Thread starter Thread starter Jimmy Dean
  • Start date Start date
J

Jimmy Dean

I have a small LAN - 3 WinME PCs (which work well thank you) and one
WinXP Pro PC.

When I copy say 500 MB/44 files from a WinME PC to the XP PC using
Windows Explorer on the Me PC, I get transfer rates 4-6 MB/s - not
fantastic but OK.

When I copy the other way - XP -> Me using Windows Explorer on the XP
PC, rates are typically 1.2 MB/s.

And...
when I copy from XP to Me, but using Windows Explorer on the Me PC,
the rate is 4-5 MB/s!!

No changes, same NICs, cables, switches only the direction (and Win
Explorer version) is different.

Replacing the Skymaster switch with a Netgear one made no difference.

Can someone explain this

thanks
jd
 
JD - similar issue here - XP Pro to XP home 500M in 2hours regardles of
doing a DOS copy or a drag and drop.
100mbs full duplex switched, all Netgear equipment, no other network traffic
etc. There are some knowledge base articles out there. Specifically I
think the SMB signing is stuffed in both XP pro and XP home. Even did a
direct crossover connection and same issue.

Will keep you informed of our progress in case it's the same issue.

Regards, CIndy
 
JD - similar issue here - XP Pro to XP home 500M in 2hours regardles of
doing a DOS copy or a drag and drop.
100mbs full duplex switched, all Netgear equipment, no other network traffic
etc. There are some knowledge base articles out there. Specifically I
think the SMB signing is stuffed in both XP pro and XP home. Even did a
direct crossover connection and same issue.

Will keep you informed of our progress in case it's the same issue.

Regards, CIndy
Click to expand...

Thanks Cindy.

Wow! or something like 70 KB/s - I should complain!

Will let you know if I find something -"LAN file copy anomaly"

cheers
jd
 
Search support.microsoft.com using the keyword "TcpDelAckTicks" . See if a
variation on these solutions solves your problem. If you have a network
sniffer you can easily see what if causing the delays (or decrease in
performance) by checking the 'delta times' between packets. Cheers!
 
Well, first of all, 6MBps is 48Mbps, which is more than just OK. It's
very good for Windows machines. It's not even bad for a pair of Unix
machines, depending on the bus speed and NIC cards of the machines involved.
I'm assuming this is 100BaseT. In any case, it sounds to me like a latency
problem. Given you are using Windows Explorer, this doesn't surprise me,
much.

I assume you have tried a ping between workstations? I gather these
machines are all on one physical LAN segment? In that case, the LAN latency
should be less than a millisecond. TCP connection rates are absolutely
limited by latency and the size of the TCP receive buffer on the target
machine. I don't know for certain what sizes the receive buffers are for
either XP or Me, but since Me is based on the Windows 98 Kernel, I suspect
it may be 8K, and since XP is optimized for networking, I suspect its
default is at least 16K or 32K.

With an 8K TCP receive buffer and a 1ms latency, the maximum connection
rate is right at 65Mbps, or about 8MBps. In larger, more diverse networks,
the link latency may be significantly higher, making any delays internal to
the machines less of a factor. In your case, however, any delays of even a
few hundred microseconds could cause the overall latency to increase
significantly.

That said, I wouldn't ordinarily expect any internal delays to be on the
order of 7ms, which is what would result in a 1.2Mbps transfer rate, but if
upping the default TCP receive buffer on the target machine increases the
transfer rate, then that is precisely what is happening, and it is highly
likely Windows Explorer is the culprit.
 
Thanks for the lengthy response.

Well, first of all, 6MBps is 48Mbps, which is more than just OK. It's
very good for Windows machines. It's not even bad for a pair of Unix
machines, depending on the bus speed and NIC cards of the machines involved.
I'm assuming this is 100BaseT. In any case, it sounds to me like a latency
problem. Given you are using Windows Explorer, this doesn't surprise me,
much.

I assume you have tried a ping between workstations? I gather these
machines are all on one physical LAN segment? In that case, the LAN latency
should be less than a millisecond. TCP connection rates are absolutely
limited by latency and the size of the TCP receive buffer on the target
machine. I don't know for certain what sizes the receive buffers are for
either XP or Me, but since Me is based on the Windows 98 Kernel, I suspect
it may be 8K, and since XP is optimized for networking, I suspect its
default is at least 16K or 32K.
Click to expand...

Yes latency either way is < 1 ms
With an 8K TCP receive buffer and a 1ms latency, the maximum connection
rate is right at 65Mbps, or about 8MBps. In larger, more diverse networks,
the link latency may be significantly higher, making any delays internal to
the machines less of a factor. In your case, however, any delays of even a
few hundred microseconds could cause the overall latency to increase
significantly.

That said, I wouldn't ordinarily expect any internal delays to be on the
order of 7ms, which is what would result in a 1.2Mbps transfer rate, but if
upping the default TCP receive buffer on the target machine increases the
transfer rate, then that is precisely what is happening, and it is highly
likely Windows Explorer is the culprit.
Click to expand...

It happens even with other file managers such as ZTreeWin or Beyond
Compare.

It seems to depend on which PC the file copying prog resides. If it
resides on PC(XP) copying is very slow, regardless of whether the
transfer is PC(XP) to PC(Me) or vice versa. OTOH, if the file copy
prog resides on PC(Me), copying is fast again independent on copy
direction.

BTW where do I set the TCP receive buffer size - can't find it in
network neightbourhood, TCP/IP or the NIC properties.

thanks
jd
 
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