I have a couple of 
customers that have been complaining of issues on their circuits, an issue that 
causes them to have problems with large file transfers. The only noteworthy 
problems in their data streams seem to be TCP Dup Acks – I’ve seen as many as 
sixty, or over a hundred, in file transfers of 100 MB test files. However, as 
near as I can determine, these errors are being introduced in the Internet, 
outside of our network (the customers use VPNs over internet circuits with major 
carriers for these file transfers).
 
As I said, we’ve tested 
our own network thoroughly, but I’m at a loss as to where to go with this issue. 
Obviously, telling the customer, “It’s not our fault” is unacceptable, as that 
doesn’t move them any closer to error-free file transfers. On the other hand, 
I’m not sure where to tell the carriers’ help desk technicians to look for the 
source of this issue. Has anyone seen this before on Internet circuits, and is 
there some way I can use Wireshark to help pinpoint the issue more specifically 
than telling the carrier, “It’s in your cloud”?
 
Thanks,
 
Roland 
Volz
Network 
Engineer
Data 
Access/Datapatch, Inc.
40 Eisenhower 
Drive
Paramus, NJ 07652-1404
(201) 843-5468 
x7032
www.Data-Access.com