I don't know the answer to 13, but are you sure they refer to minutes and not seconds? It would be insane to retransmit a packet for half hour or so and 30 seconds at most sounds more reasonable.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Kan-I Jyo Sent: Tuesday, January 18, 2011 10:49 AM To: Red Hat Enterprise Linux 5 (Tikanga) discussion mailing-list Subject: [rhelv5-list] [QA] net.ipv4.tcp_retire2 and TCP_RTO_MIN Dear list I have just playing around with the sysctl interface with regard to TCP tuning parameters and just found the following from the manual: <digest from "$man tcp"> ... snip ... tcp_retries2 (integer; default: 15; since Linux 2.2) The maximum number of times a TCP packet is retransmitted in established state before giving up. The default value is 15, which corresponds to a duration of approximately between 13 to 30 minutes, depending on the retransmission timeout. The RFC 1122 specified minimum limit of 100 seconds is typically deemed too short. Just wondering where the "13 to 30 minutes" come from. >From what I have found in <include/net/tcp.h>, the "TCP_RTO_MAX" and "TCP_RTO_MIN" are defined like the following: <include/net/tcp.h> ... snip ... #define TCP_RTO_MAX ((unsigned)(120*HZ)) #define TCP_RTO_MIN ((unsigned)(HZ/5)) #define TCP_TIMEOUT_INIT ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value */ The TCP_RTO_MAX is like "120*1=120", as a result we may wait for "120*15/60=30" minutes for a timeout, just like the manual say. On the other, I just could not find some clue where the minimal "13 minute" comes from. Could anyone shed me some light on this? -- Sincerely, Jyo _______________________________________________ rhelv5-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/rhelv5-list _______________________________________________ rhelv5-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/rhelv5-list
