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[lwip-devel] [patch #9751] UDP client/serveur support in lwiperf


From: David GIRAULT
Subject: [lwip-devel] [patch #9751] UDP client/serveur support in lwiperf
Date: Wed, 30 Jan 2019 12:44:24 -0500 (EST)
User-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36

Follow-up Comment #4, patch #9751 (project lwip):

According to the delay_target calculation, since buf_len is constant 1470 (or
1450 with IPv6), the calculated delay is:
- 11760µs for 1Mb/s (1000000)
- 1176µs  for 10Mb/s (10000000)
- 373µs   for 30Mb/s (30000000)

Using a timing limited to one microsecond granularity will limit the maximum
UDP bw to 11.76Mb/s.

WiFi certification require UDP bandwidth you can't achieve sending one frame
each millisecond (sorry don't remember the required bw for WiFi N test plan).

You can send more frame for each millisecond but this will impact the
calculation of jitter at the receiving endpoint.

May be we can have a new `u64_t sys_now_us()` to allow fine grained timing in
lwIP ? Defaulting to `sys_now()*1000`.

This let user providing whatever implementation they want. If not provided
maximum UDP bandwidth will be limited.


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