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
