Hi, we have a link with 70Mbits upload/download with UDP and about 60Mbits TCP U/D with 20 connections. The link is N mode with 40MHz nstreme, only bridging and routing.
When using standard Internet speedtests on one side of this link, the result on this link is a ‘horrible’ 14Mbits (they use a single TCP upload connection? ).
When we run two of them at the same moment, we get two ‘horrible’ 14Mbits, to sum a total of ‘not so horrible’ 28Mbits… and so on.
Which is the technology that splits the bandwidth?
Is there a way to ‘aggregate’ those multiple 14Mbits TCP streams in one?
You will see that single TCP connection speed is strongly affected by
a) Round-Time Trip (RTT) time - ping to there and back
b) Maximum Segment Size (MSS) - amount of data per packet
c) TCP Window size of both endpoints (default is 64K)
There are lots of materials about this, just search for it.
Ok, this sounds good… but there is something I did not mention… if you run the tests in the oposite direction, it reaches the correct speed.
If I undersatand what you explain, the results on both directions should be the same (as window sizes and roundtrips should be the same). Any ideas on how can this be ‘asymentric’?
To what are you connected? Cable, Adsl, fibre? What kind of contract?
Most connections are not symmetric. Usually bandwidth TO end user is more than FROM end user.
Well Ok.
I have a symmetric line myself. 20Mb up and down.
But if I run a www.speedtest.net I get the full 20Mb download, but hardly ever more than 10,11Mb upload.
Only if I run that test on two or three PC’s with their own public IP’s I get to the full 20Mb upload.
Why that is the case is also not so clear to me.
Asked the provider and they don’t even understand my question. I reach both speeds in both directions. So what is my problem?
Sometimes I’ve had TCP problem with devices’ ethernet port in “autonegotiation”. I that case one connection didn’t reach maximum bandwidth, but more connections yes. Setting ethernet ports at 100 Mbps Full Duplex solved problem.
If you want to set ethernet speed remotely pay attention if you are using straight or cross cable connecting devices. If cable is incorrect result could be an ethernet link down.
@Wirelessrudy: I think problem is probably on ISP side. I’ve had the same problem with more than one line. Download was maximum with one TCP connection, upload was maximum only with 2/3 connections or above. No issue with UDP.
I’ve asked my ISP and it said there’s no problem. Insisting, it has solved on some lines but not on others because “there’s not any problem”. But I don’t think so…
