Re: [Cake] The two SCE tests I have in mind

[Pete Heist <pete@heistp.net>]

> On Mar 24, 2019, at 9:55 AM, Dave Taht <dave.taht@gmail.com> wrote:
> 
> 1) The research into whether bit flipping to the extent that SCE will
> do has not been done yet. The study of ECT(0) vs ECT(1) behavior
> transiting to CE was a little lightweight.
> 
> To test this we going to fire up a ton of nanodes in various data
> centers, with low SCE thresholds, and low bandwidths, to flip lots of
> bits, and test between the data centers and from as many vantage
> points around the net as we can get - do packet captures as well as
> flent tests
> 
> as a control, set up identical boxes, with SCE disabled, in the same
> data centers.
> 
> Setup flent, irtt, iperf3.

Sounds good, I’ll offer my home setup with a couple APU2s as a “residential WISP” vantage point. I was unable to access it with OpenVPN from the boat but I’ll sort that out before I go.

> 2) Diffserv bit preservation test
> 
> The research going by on the tsvwg mailing seems a bit dated. It is
> very straightforward to use irtt to test to see what udp codepoints
> survive e2e, and to also leverage this testbed setup. Similarly,
> netperf can easily be used to mark tcp. We do not have a good packet
> cap tool to verify that the bits are being set right, however I think
> irtt can be modified to check for correctness here and produce a
> report.

The irtt server knows what codepoint was negotiated and could easily emit a log message if incoming packets don’t match, but unfortunately the codepoint of incoming packets is not available without using a raw conn (requires root). We’ll want that anyway for UDP lite and I’ll see what’s possible tonight, but for now we can also just use a simple tcpdump filter like this:

tcpdump -r file.pcap udp port 2112 and greater 80 and "ip[1] != 0x1”

“greater 80” ignores the handshake packets and 0x1 is whatever TOS value we want to make sure the packets contain. We can use different filters for other traffic.

> On Sun, Mar 24, 2019 at 1:45 AM Jonathan Morton <chromatix99@gmail.com> wrote:
>> 
>>> On 24 Mar, 2019, at 8:37 am, Pete Heist <pete@heistp.net> wrote:
>>> 
>>> I should theoretically arrive at the boat today some time after 3pm, having picked up a mini HDMI to HDMI adapter, which we can use with the cable that’s there…
>> 
>> Awesome.  I'm also setting up a Linux VM on my Mac, which should help things along.
>> 
>> We're bringing up some actual hardware with the SCE-enabled Cake on it now.  Dave wants to investigate various theoretical phenomena the Internet might exhibit with a mixture of ECN codepoints; I just want to be sure it actually works as intended, before I move on to fiddling with TCP.
>> 
>> - Jonathan Morton
>> 
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> 
> 
> 
> -- 
> 
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-205-9740