linux/include
Damian Lukowski 6fa12c8503 Revert Backoff [v3]: Calculate TCP's connection close threshold as a time value.
RFC 1122 specifies two threshold values R1 and R2 for connection timeouts,
which may represent a number of allowed retransmissions or a timeout value.
Currently linux uses sysctl_tcp_retries{1,2} to specify the thresholds
in number of allowed retransmissions.

For any desired threshold R2 (by means of time) one can specify tcp_retries2
(by means of number of retransmissions) such that TCP will not time out
earlier than R2. This is the case, because the RTO schedule follows a fixed
pattern, namely exponential backoff.

However, the RTO behaviour is not predictable any more if RTO backoffs can be
reverted, as it is the case in the draft
"Make TCP more Robust to Long Connectivity Disruptions"
(http://tools.ietf.org/html/draft-zimmermann-tcp-lcd).

In the worst case TCP would time out a connection after 3.2 seconds, if the
initial RTO equaled MIN_RTO and each backoff has been reverted.

This patch introduces a function retransmits_timed_out(N),
which calculates the timeout of a TCP connection, assuming an initial
RTO of MIN_RTO and N unsuccessful, exponentially backed-off retransmissions.

Whenever timeout decisions are made by comparing the retransmission counter
to some value N, this function can be used, instead.

The meaning of tcp_retries2 will be changed, as many more RTO retransmissions
can occur than the value indicates. However, it yields a timeout which is
similar to the one of an unpatched, exponentially backing off TCP in the same
scenario. As no application could rely on an RTO greater than MIN_RTO, there
should be no risk of a regression.

Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-09-01 02:45:47 -07:00
..
acpi Revert "ACPICA: Remove obsolete acpi_os_validate_address interface" 2009-07-27 18:42:38 -04:00
asm-generic Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2009-08-12 17:44:53 -07:00
crypto
drm drm/radeon: Add support for RS880 chips 2009-08-05 12:07:09 +10:00
keys
linux dcbnl: Add support for setapp/getapp commands to dcbnl 2009-09-01 01:24:30 -07:00
math-emu
media V4L/DVB (12283): gspca - sn9c20x: New subdriver for sn9c201 and sn9c202 bridges. 2009-07-24 14:03:30 -03:00
mtd
net Revert Backoff [v3]: Calculate TCP's connection close threshold as a time value. 2009-09-01 02:45:47 -07:00
pcmcia
rdma
rxrpc
scsi
sound
trace net: skb ftracer - add tracepoint to skb_copy_datagram_iovec (v3) 2009-08-13 16:26:14 -07:00
video
xen
Kbuild