elders of t3h interwebz! i seek your wisdom for a rather strange matter...
i am working on a case: a small network involving a Window Server 2012 R2 machine configured as a router, RADIUS server for wireless and also used for general network storage.
the network goes: Cisco router > server > wireless AP & computer
the server has 3 NIC's:
- mainboard Realtek Gbit controller - connected to wireless AP > other wireless devices
- PCIE Intel ET dualport adapter:
- Port 1 - connected to desktop pc
- Port 2 - connected to router
the network is not a domain, and technically the whole setup works fine; hosts are talking to the server, server monitors all connections, everyone has internet and no latency or dropout problems...
the issue here is: the throughput.
the premises has ADSL2+ that, on speed tests i did on my laptop with a straight connection to the router, reaches 20Mbps download (router reports line at 22Mbps). but the server is only getting 15Mbps at best, and so do all subsequent connections that run through the server.
at first i thought this could be a driver issue, so did the usual, no help. then i thought it could be hardware, and tried changing to different NICs for the router connection, still no good. always getting 14~15.
also tried disabling flow control, interrupt mod, power saving features, TCP RWIN autotuning and SMB signing, and checked offloading and RSS options, also increased the transmit and receive buffers... none of them helped.
i am a little out of ideas at this stage, there seems to be some sort of bandwidth control throttling the connection, but i cannot identify what and why ><
inputs and comments much appreciated ^^ much <3 and thanks!