NDT-DEV email list created

[Richard Carlson <>]

Don;

Forgive me for sounding like a broken record on this topic, but the NDT 
(Network Diagnostic Tool) system was specifically designed to go beyond 
merely reporting up/down load speeds.  The server captures dozens of TCP 
variables and analyzes them to identify why a given result was posted.

You don't need to guess if there were packet retransmissions, the NDT 
server tells you that.  You don't need to guess if the delay is high, 
low, or varying, just look at the test results.  You don't need to guess 
if the client's configuration is limiting throughput, just look at the 
test results.

If the results given at the end of the test aren't enough, then turn on 
more diagnostics, capture the packet trace, get TCP variables at 5 msec 
intervals for the 10 sec test.  Use the data that's being collected, and 
reported, to better understand what is going on.

If you need help reading the test results, post a question to the 
ndt-dev email list.  We'll be glad to help walk you through the results.

What I would start looking at is,

What is the TCP window size set to?  The 100% increase in speed between 
Calgary and Montreal probably means the receive window is the limited 
factor.  (assuming the RTT to Montreal is 2x the RTT to Calgary). Then 
look at the time spend in the various states.  Sitting in the send or 
receive states indicates a host resource issue.   Look at the number of 
packets sent/ack's received.

Given that the Websocket Upload numbers are 10x lower than the others, 
I'd wonder if there isn't a math error in the code somewhere and you are 
simply seeing a reporting error, not a testing error.  Looking at the 
packet traces and other diagnostic data will quickly point out that type 
of code bug.

Rich (NDT grandfather).

On 07/08/2015 01:38 PM, Don Slaunwhite wrote:
> Hi Jordan,
>
> It seems we may have multiple email threads going on about this issue. I'll 
> respond with details on the other thread. 8) But to help clarify for the 
> people here.
>
> We were running a Windows 2012 Server  as the Amazon VM. At first we chose one with 
> "Low" network bandwidth, but we also created another with "High" network 
> bandwidth. On those Windows machines we have testing software which runs our IPT test through the 
> Chrome browser. It basically just goes flash then websocket etc. The times between runs is 
> roughly 30 seconds and we let it run overnight.
>
> We did see slower values coming from the Toronto site, so we ran the same 
> tests to Calgary and Montreal. Those sites gave us much better results (in 
> both Flash and Websocket) but still Flash was significantly faster. I'm not 
> sure if it is our implementation of the Flash/websockets client or what.
>
> For instance in Montreal
>
> Flash Upload - 304Mbps
> Flash Download - 220Mbps
> Websocket Upload - 45Mbps
> Webscoket Download - 230Mbps
>
> And in Calgary
>
> Flash Upload - 616Mbps
> Flash Download - 542Mbps
> Websocket Upload - 44Mbps
> Webscoket Download - 472Mbps
>
> So even on other servers we are definitely seeing a degradation of Websocket 
> upload. Now perhaps it truly is something with the VM. But even then it seems 
> a bit odd. We have no firewall/anti-virus on. What sort of things have you 
> seen gone wrong with VM testing?
>
> We did do some external real life testing via our employee's home systems 
> (not through VPN etc) and we still saw slower Websocket speeds. (But not 
> anything of this magnitude of difference.)
>
> For example:
>
> (about 200 tests from around Ottawa)
>
> 20.8 Mbps - Flash Chrome Download Avg
> 3.034 Mpbs  - Flash Chrome Upload Avg
> 21.2 Mpbs - Websocket Chrome Download Avg
> 2.56 Mpbs - Websocket Chrome Upload Avg
>
> So not as big a difference, but still large enough to wonder. Then combined 
> with the VM testing above.
>
> Do you have a dataset from your testing that we could look at? Honestly if 
> you have a good sample size of data that we can feel comfortable with, then 
> we can start looking at what exactly on our implementation is going wrong. 
> (if it is indeed our implementation.)
>
> Thanks,
> Don
>
>
> -----Original Message-----
> From: Jordan McCarthy 
> [mailto:]
> Sent: July-07-15 3:53 PM
> To: Don Slaunwhite
> Cc: 
> ;
>  
>
> Subject: Re: [ndt-dev] Websocket Client - Upload Speed Problem
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>
> Hi everybody,
>          We've also been monitoring the performance characteristics of the 
> WebSockets client closely, both before and after the client's official 
> publication in NDT 3.7.0, and we haven't been able to reproduce the disparity 
> that CIRA has encountered.  We've run Websocket-based tests from several 
> different browser combinations on a variety of operating systems and 
> consumer-grade connections, during various times of the day, and haven't 
> encountered any appreciable differences (within any given 
> machine/connection/time of day combination).  Additionally, for the sake of 
> thoroughness we've run C-client tests from the same connections, and the 
> numbers we got from the C client runs were pretty comparable with what we 
> were getting out of all of the Websockets tests.
>
> Don: could you tell us a little bit more about your testing methodology?  I'm 
> guessing you spun up a Linux VM, and used X-forwarding to get access to an 
> instance of the browser running on the VM?
>
> Off the top of my head that sounds reasonable, but we've definitely seen 
> weird artifacts introduced by running tests out of VM environments, so 
> perhaps that could be throwing things off somewhat.
>
> Jordan
>
> Jordan McCarthy
> Open Technology Institute @ New America
> Public Key: 0xC08D8042 | 4A61 3D39 4125 127D 65EA DDC2 BFBD A2E9 C08D 80
> 42
>
> On 07/06/2015 02:45 PM, Don Slaunwhite wrote:
> > Hi Everyone,
> >
> >
> >
> > My name is Don Slaunwhite and I’m a Product Manager at CIRA. We have
> > been utilizing the NDT tests as part of our Internet Performance Test
> > up here in Canada.
> >
> >
> >
> > We have been working on transitioning to the Websocket client with our
> > test, but we have been seeing some very different results in upload
> > speeds as compared to the flash client.
> >
> >
> >
> > We did a lot of internal/external testing and in every case the upload
> > speeds for the websocket version were lower (most times
> > significantly) than our current flash client. The download speeds are
> > comparable, with websocket usually coming in a bit faster
> >
> >
> >
> > For example we setup a VM at Amazon to run some (hopefully!)
> > controlled tests. Using Chrome and Firefox.
> >
> >
> >
> > Chrome Averages based on ~200 tests
> >
> > Flash 19.3Mpbs Upload
> >
> > Flash 49.8Mpbs Download
> >
> > Websocket  9.3Mpbs Upload
> >
> > Websocket  54.3Mpbs Download
> >
> >
> >
> > Firefox Averages based on ~300 tests
> >
> > Flash 27.4 Mpbs Upload
> >
> > Flash 50.1 Mpbs Download
> >
> > Websocket  11.1 Mpbs Upload
> >
> > Websocket  57.2 Mpbs Download
> >
> >
> >
> > In each case the websocket upload is significantly lower. I’m trying
> > to determine if this is expected behaviour with the websocket code. If
> > not what possible items might be causing this type of speed
> > degradation.
> >
> >
> >
> > We are running with client versions 3.7.0 (Flash has a buffer size of
> > 32K) against mlab servers in Toronto.
> >
> >
> >
> > I realize there will be new functionality/capability with the multiple
> > stream releases, but right now I’d like to try and focus on one major
> > change at a time, so any ideas on speed differences between Flash and
> > Websocket using just 3.7.0 would be really helpful.
> >
> >
> >
> > Thanks,
> >
> > Don
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