packet delay because of blackhole

[Anthony Pankov]

Just for somebody convince.

While analyzing client<->server HTTPS conversation one second delay in
packet exchange was discovered (strongly reproducible):

Sample:
N        time
6       0.002303        10.28.4.14      10.28.4.50      SSL     Client Hello
7       0.106710        10.28.4.50      10.28.4.14      TCP     443 > 1447 [ACK] Seq=1 Ack=103 Win=65535 Len=0
8       1.045712        10.28.4.50      10.28.4.14      TLSv1   Server Hello, Certificate, Server Hello Done

Another sample:
10      0.011722        10.28.4.14      10.28.4.50      TLSv1   Application Data
11      0.115933        10.28.4.50      10.28.4.14      TCP     443 > 1442 [ACK] Seq=839 Ack=519 Win=65466 Len=0
12      1.054037        10.28.4.50      10.28.4.14      TLSv1   Application Data

The reason for delay is sysctl tcp.blackhole value grater than 0, much to surprise.

So, turning tcp.blackhole to 0 eliminate any delay (strongly reproducible).

System: FreeBSD 6_2_stable

-- 
Best regards,
 Anthony                          mailto:ap00 at mail.ru


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