Network round-trip latency
Netperf's request/response tests measure the number of "transactions" completed over a given period of time. A "transaction" is defined as the exchange of a single request and a single response. Netperf supports request/response testing for both TCP and UDP, and it can be configured to use a custom request and response size.
For this test, we swapped between the Intel and the Killer GigE controllers. The other hardware and software on the system remained the same. Thus, any differences in the average round trip latency that we see in this testing should be due to the NIC in use and its driver.
Netperf is usually distributed as source code, so pre-built binaries for Windows are usually only made available by third parties. Not all versions of the software are easy to come by. For this test, we used the pre-built netperf 2.4.5 binary from this source for Windows. On our Linux server, we built netperf 2.4.5 from source.
We ran the following command on our test system:
netperf.exe -l 30 -t TCP_RR -L 192.168.1.25 -H 192.168.1.40 -c -- -r size,size
..with the server set up to listen on the following IP address:
netserver -L 192.168.1.40
Once again, our test system was connected to the server using a crossover CAT6 cable.
Netperf reports the number of transactions performed per second over the duration of the test, which we inverted to turn into an average round trip latency. The CPU usage numbers were taken directly from the Netperf output. These tests were run three times, and we reported the median result.
First up, some TCP round trip latency tests:
With a request and response size of just one byte, we are effectively finding the minimum time it takes to get a TCP packet out on the wire and to receive the response from the server. The Killer's results are impressive. The Intel's I219-V's minimum round trip latency is 38.3 microseconds, or 71%, longer than the Killer E2400's.
Obviously, both NICs are using the same underlying Windows networking stack, so we've now found a test where the low-latency tuning that the Killer folks have done can be measured. But, what does the CPU usage look like for this test?
Impressively, the Killer is no hungrier for your precious CPU cycles in this test than the Intel controller.
Round trip latency for a single byte test is interesting for finding the minimum path length through the network and driver stack, but it's somewhat academic. Let's see what happens when we increase the size.
With a 32-byte payload, the results are even more impressive. Here, the Killer has a round-trip latency that is under one-third of what the Intel controller achieves.
And it does so using a comparable amount of host CPU cycles.
Once we reach sizes of 128 bytes, the Killer's lead shrinks to 4.7%. CPU usage between the two competing connectivity solutions is still comparable, though.
When sending and receiving 512 bytes, the Killer's round trip latency is 12.5% less than the Intel. CPU usage for the Killer looks a little higher, but only by 0.3%.
Using the standard drivers, without the rest of the Killer software stack, and enabling or disabling Bandwidth Control in the Killer Suite resulted in no meaningful differences in performance or CPU usage.
Most online multiplayer games rely on UDP instead of TCP, though. With that fact in mind, we ran through these same tests using netperf's UDP request/response mode.
Similar to last time, we ran the following command on our test system:
netperf.exe -l 30 -t UDP_RR -L 192.168.1.25 -H 192.168.1.40 -c -- -r size,size
..and once again, the server was set up to listen on the following IP address:
netserver -L 192.168.1.40
These results don't perfectly mirror the average round-trip latencies we saw for TCP packets, but the trend is the same for UDP datagrams. The Killer outperfors the Intel controller by a wide margin at small request-and-response sizes, and the margin shrinks as the size increases. The Killer's CPU usage is higher than Intel's, but not more than 1% higher in these tests.
Since most games rely on UDP datagrams of 128 bytes or less, the above results show the Killer NIC is doing its part to minimize the client-side latency. Once your network traffic leaves your home router, however, that data has to fend for itself out on the Internet. With that in mind, your online gaming experience depends on more than which Gigabit Ethernet controller you're using. That said, minimizing the time game data spend in the depths of your PC obviously can't hurt.
Now that we've thoroughly exhausted our network performance tests, let's look at what else Killer's software suite can do for us.
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