Progressively slower transmission and potential buffer handling issue. about wifi101 HOT 5 OPEN

This was my fault! An errant component was frequently toggling IRQs during the network handling and as soon as that was cleared away things started to behave much better. Sorry for the noise.

from wifi101.

Hey everyone.... I slimmed down my test case, pulling in the SimpleWebServer example and making a few modifications:

1. I buffer all the HTTP headers into one write call.
2. The server sends a Content-Length of 1MB and produces that data as a stream of 1400 byte blocks. Each block is filled with the same byte, incremented on each block (1400 0's, 1400 1's, etc...) So packets are easy to see the local order of.

I then issued a curl command on my desktop to download while I took a Wireshark capture.

Notable in the capture is that things don't appear to be going smoothly from the beginning haha. It starts with a missing TCP segment, which should have been captured and then sputters through some more of those and out of order TCP and then eventually degrades into a whole flood of TCP retransmissions.

Which if I'm understanding the behind the scenes makes sense, as those retransmission's are only possible if the data is still around, and that's a lot of data to keep around, hence my buffering and speed issues.

Jacob

winc1500-slow-1MB-2.pcapng.gz

from wifi101.

In an effort to eliminate variables I moved my WiFi closer to the hardware and reran the test. First test went really well, and then the second test went south on me. I've uploaded the pcap from that test, as well which I think may demonstrate the problem better as things appear fairly smooth and then the problems become extremely visible.

I'm running these curl's from a wired connection on the same router serving the WiFi, by the way. Things don't get any better when both ends are on the WiFi.

winc1500-1MB-closer-wifi-2.pcapng.gz

Jacob

from wifi101.

I should note that the previous capture was done running the whole code/stack that originally exhibited the problem and appears more difficult to reproduce when I narrow the code down the my test case based on SimpleWebServer. I'm going to keep digging to see if something I'm doing is exacerbating this problem in that case.

Jacob

from wifi101.

I spoke too soon. This is still an issue for me and I believe my prior work was just making my own code less of an factor. Closer WiFI for easier testing made the issue less likely to surface, but now that I've returned everything to their rightful positions it's back with a vengeance.

from wifi101.