Re: [lwip-users] lwip reply delayed after long communication idle time

[Jochen Strohbeck]

Now, in 2.1.x, the first http request after host and controller power up is
served but still delayed for ca. 5s and I don't know if this is a "feature"
or bug of ARP.
Please have a look at the commented 1st trace below.
The second trace shows the normal behavior. The controller immediately sends
out a ARP broadcast after receiving the first TCP msg. For me the host is
expecting this broadcast but this is missing in the first trace.

Who is to blame for the delay? The http server or the host? How to get rid
of the delay if possible? I'm on windows 10.

1880    73051.473650    de:bd:00:00:00:29       Broadcast       ARP     60      
ARP Announcement for
192.168.0.100
-> controller power on

1881    73205.861086    192.168.0.9     192.168.0.100   TCP     66      57961 → 
80 [SYN] Seq=0
Win=64240 Len=0...
-> 1st http.get() request after power up (python requests)

1882    73208.861658    192.168.0.9     192.168.0.100   TCP     66      [TCP 
Retransmission]
57961 → 80 [SYN] Seq=0 Win=64240...
-> retrans after 3s

1883    73210.857278    Dell_7a:2c:51   de:bd:00:00:00:29       ARP     42      
Who has
192.168.0.100? Tell 192.168.0.9
-> host ARP request after 2s

1884    73210.861936    192.168.0.9     192.168.0.100   TCP     66      57962 → 
80 [SYN] Seq=0
Win=64240 Len=0 MSS=1460 WS=2...
1885    73210.862961    de:bd:00:00:00:29       Broadcast       ARP     60      
Who has 192.168.0.9?
Tell 192.168.0.100
1886    73210.862988    Dell_7a:2c:51   de:bd:00:00:00:29       ARP     42      
192.168.0.9 is at
98:e7:43:7a:2c:51
1887    73210.863678    de:bd:00:00:00:29       Dell_7a:2c:51   ARP     64      
192.168.0.100 is at
de:bd:00:00:00:29
1888    73210.863679    192.168.0.100   192.168.0.9     TCP     60      80 → 
57962 [SYN, ACK]
Seq=0 Ack=1 Win=2920 Len=0 MSS=1460
:

1990    74227.892538    de:bd:00:00:00:29       Broadcast       ARP     60      
ARP Announcement for
192.168.0.100
1991    74248.600750    192.168.0.9     192.168.0.100   TCP     66      58120 → 
80 [SYN] Seq=0
Win=64240 Len=0 MSS=1460...
1992    74248.601430    de:bd:00:00:00:29       Broadcast       ARP     60      
Who has 192.168.0.9?
Tell 192.168.0.100
1993    74248.601456    Dell_7a:2c:51   de:bd:00:00:00:29       ARP     42      
192.168.0.9 is at
98:e7:43:7a:2c:51
1994    74248.601813    192.168.0.100   192.168.0.9     TCP     60      80 → 
58120 [SYN, ACK]
Seq=0 Ack=1 Win=2920...




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