We have a need to transfer about 50GB of data from a Windows 2003 server at a remote site across a gig WAN circuit to a Windows 2008 server at our data center. When we try to send that traffic over the nearly-empty gig link, bandwidth use never exceeds about 12M or so. We do use that link for database-syncing, and that process can use about 980Mbps, so the link is fully capable of carrying the traffic. We suspect bandwidth-delay-product might factor in here, or perhaps some limit built into Windows 2003, but if somone can give us a definitive answer, we would be grateful.
Router hardware: Cisco 3945e on each end for the gig link.