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I have a situation where I need best possible throughput (TCP/IP sockets & SMB3) between two Windows Server 2016 connect with a 1m patch cable.

I have to use existing hardware.

When you connect two Windows Server 2016 machines together directly, without using a switch, you should be able to get better performance since you know there is only two computers on the subnet.

The question is, which parameters to tune, and what set those parameters to? I have been looking at the parameters on the drivers for the network cards, but I guess that there are settings in windows as well that affect the network stack and how TCP/IP, RPC, named pipes and so on behave.

Both machines are Dell R430 with Intel Ethernet I350 QP 1Gb Server Adapter.

The "front" machine is connected the the normal network through one nic, and to the "backend" machine through a 1m patch cable on another nic. The "backend" machine is only connected to the "front" machine.

NoOneSpecial
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1 Answers1

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Using TCP over gigabit Ethernet, there shouldn't be any difference between direct connection or a switch in between (unless the switch is ancient). For the last two decades, switches have been running at "wire speed" = forwarding as fast as is physically possible.

A switch introduces a tiny, additional latency into the connection (in the order of 2 to 10 µs). Unless the protocol in use is extremely sensitive to latency you won't see any difference. Especially TCP handles latencies well.

Also, when using a switch there's next to no penalty for other computers on the network unless their traffic shares a single link that's already running at full capacity.

With a fairly decent network design you can run streams across the entire network and a number of switches that run at close to 100% of the link speed.

With current Windows versions, the IP stack is already set up or very good performance by default. I haven't had to tweak the parameters in many years.

Make sure you've got current drivers installed and the offloading features in the NICs are turned on.

When gigabit speed isn't enough you can aggregate multiple links (this is where the fun starts) or replace the NICs with 10GE ones (much simpler but more costly).

Zac67
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  • so there are no settings like flow control, or settings for detecting/avoiding collisions or anything like that that can optimized when we know there are only two computers on the physical network? – NoOneSpecial Apr 28 '18 at 22:05
  • Flow control is rarely useful and collisions are a thing of the past, especially with gigabit upwards. – Zac67 Apr 28 '18 at 22:10