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BubbleTrouble

Occasional Visitor
I have been using iPerf3 on my LAN to test speeds and am getting the following results between my two PCs (PC1 and PC2) which are connected using gig ethernet and are both connected directly to my switch.

c:\iperf>iperf3.exe -c 192.168.0.13 -p 3000
Connecting to host 192.168.0.13, port 3000
[ 4] local 192.168.0.2 port 54997 connected to 192.168.0.13 port 3000
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 109 MBytes 916 Mbits/sec
[ 4] 1.00-2.00 sec 113 MBytes 948 Mbits/sec
[ 4] 2.00-3.00 sec 113 MBytes 944 Mbits/sec
[ 4] 3.00-4.00 sec 112 MBytes 942 Mbits/sec
[ 4] 4.00-5.00 sec 112 MBytes 942 Mbits/sec
[ 4] 5.00-6.00 sec 112 MBytes 944 Mbits/sec
[ 4] 6.00-7.00 sec 112 MBytes 944 Mbits/sec
[ 4] 7.00-8.00 sec 112 MBytes 943 Mbits/sec
[ 4] 8.00-9.00 sec 113 MBytes 945 Mbits/sec
[ 4] 9.00-10.00 sec 112 MBytes 943 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 1.10 GBytes 941 Mbits/sec sender
[ 4] 0.00-10.00 sec 1.10 GBytes 941 Mbits/sec receiver

I then run the test from my PC1 to my PC3(connected using a powerline homeplug) and get these results:

c:\iperf>iperf3.exe -c 192.168.0.3 -p 4000
Connecting to host 192.168.0.3, port 4000
[ 4] local 192.168.0.2 port 55002 connected to 192.168.0.3 port 4000
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 25.8 MBytes 216 Mbits/sec
[ 4] 1.00-2.00 sec 24.9 MBytes 209 Mbits/sec
[ 4] 2.00-3.00 sec 24.1 MBytes 202 Mbits/sec
[ 4] 3.00-4.00 sec 25.0 MBytes 210 Mbits/sec
[ 4] 4.00-5.00 sec 24.9 MBytes 209 Mbits/sec
[ 4] 5.00-6.00 sec 25.1 MBytes 211 Mbits/sec
[ 4] 6.00-7.00 sec 25.0 MBytes 210 Mbits/sec
[ 4] 7.00-8.00 sec 26.9 MBytes 226 Mbits/sec
[ 4] 8.00-9.00 sec 25.6 MBytes 215 Mbits/sec
[ 4] 9.00-10.00 sec 26.2 MBytes 220 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 254 MBytes 213 Mbits/sec sender
[ 4] 0.00-10.00 sec 253 MBytes 213 Mbits/sec receiver

could anyone confirm whether these results are what should be expected? Am I to understand correctly that powerline is limited to half duplex and uses CSMA/CA like wireless ?
also does anyone know if using the -w option to increase the packet size will be of any benefit ? for example if I use the command iperf3.exe -c 192.168.0.3 -w 4000K does this mean that a packet with size 4MB (4000KB) is sent to the iperf server in one go ?
is that realistic as I thought that TCP limits each segment to 1500bytes due to window size ?
 
could anyone confirm whether these results are what should be expected? Am I to understand correctly that powerline is limited to half duplex and uses CSMA/CA like wireless ?
also does anyone know if using the -w option to increase the packet size will be of any benefit ? for example if I use the command iperf3.exe -c 192.168.0.3 -w 4000K does this mean that a packet with size 4MB (4000KB) is sent to the iperf server in one go ?
is that realistic as I thought that TCP limits each segment to 1500bytes due to window size ?

Numbers aren't too bad for HomePlug AV1200 - might consider testing from another outlet, and jumping circuits does have some impact on speed, along with any potential noise sources near by either end of the link

(there's a good article on the Main Site regarding HomePlug performance - it's a bit dated, but all advice there is still very relevant)

HomePlug - it's different than WiFi, as the physical layer link between the different end-points (whether two or more) is scheduled - much like Token Ring from back in the day - which helps quite a bit - each node having a reserved time to speak or not... the Ethernet interface likely is full duplex itself, and in my experience, they don't do jumbo frames, even the Gigabit versions - which is ok.

IPerf can let one build really big packets at the TCP/UDP layers, but recall that is transport layer... when you get deeper into the stack where ethernet lives, those big transport layer packets are going to be broken up and fragmented across multiple ethernet layer frames at the data link layer (think ethernet, WiFi, etc...)...

In any event - the -w switch is setting the Tx Window Size, not the MTU (or MSS) size - normally this is an automatic feature of the TCP/IP stack along with the NIC driver, along with the path discovery algo's between the source and sink...

(recall in the olden days of Dial Up SLIP/PPP sessions - TCP Rwin was 4 times MTU, and MSS was MTU minus 40 bytes)

Hope this helps...
 

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