From: Mauro Carvalho Chehab Date: Thu, 30 Apr 2020 16:04:29 +0000 (+0200) Subject: docs: networking: convert tcp-thin.txt to ReST X-Git-Tag: v5.8-rc1~165^2~382^2~3 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=ff159f4f1152b7012d378c69ffd253ed53227865;p=linux-2.6-block.git docs: networking: convert tcp-thin.txt to ReST Not much to be done here: - add SPDX header; - adjust identation, whitespaces and blank lines where needed; - add to networking/index.rst. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: David S. Miller --- diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst index f53d89b5679a..89b02fbfc2eb 100644 --- a/Documentation/networking/index.rst +++ b/Documentation/networking/index.rst @@ -107,6 +107,7 @@ Contents: strparser switchdev tc-actions-env-rules + tcp-thin .. only:: subproject and html diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 38f811d4b2f0..3266aee9e052 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -886,7 +886,7 @@ tcp_thin_linear_timeouts - BOOLEAN initiated. This improves retransmission latency for non-aggressive thin streams, often found to be time-dependent. For more information on thin streams, see - Documentation/networking/tcp-thin.txt + Documentation/networking/tcp-thin.rst Default: 0 diff --git a/Documentation/networking/tcp-thin.rst b/Documentation/networking/tcp-thin.rst new file mode 100644 index 000000000000..b06765c96ea1 --- /dev/null +++ b/Documentation/networking/tcp-thin.rst @@ -0,0 +1,52 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +Thin-streams and TCP +==================== + +A wide range of Internet-based services that use reliable transport +protocols display what we call thin-stream properties. This means +that the application sends data with such a low rate that the +retransmission mechanisms of the transport protocol are not fully +effective. In time-dependent scenarios (like online games, control +systems, stock trading etc.) where the user experience depends +on the data delivery latency, packet loss can be devastating for +the service quality. Extreme latencies are caused by TCP's +dependency on the arrival of new data from the application to trigger +retransmissions effectively through fast retransmit instead of +waiting for long timeouts. + +After analysing a large number of time-dependent interactive +applications, we have seen that they often produce thin streams +and also stay with this traffic pattern throughout its entire +lifespan. The combination of time-dependency and the fact that the +streams provoke high latencies when using TCP is unfortunate. + +In order to reduce application-layer latency when packets are lost, +a set of mechanisms has been made, which address these latency issues +for thin streams. In short, if the kernel detects a thin stream, +the retransmission mechanisms are modified in the following manner: + +1) If the stream is thin, fast retransmit on the first dupACK. +2) If the stream is thin, do not apply exponential backoff. + +These enhancements are applied only if the stream is detected as +thin. This is accomplished by defining a threshold for the number +of packets in flight. If there are less than 4 packets in flight, +fast retransmissions can not be triggered, and the stream is prone +to experience high retransmission latencies. + +Since these mechanisms are targeted at time-dependent applications, +they must be specifically activated by the application using the +TCP_THIN_LINEAR_TIMEOUTS and TCP_THIN_DUPACK IOCTLS or the +tcp_thin_linear_timeouts and tcp_thin_dupack sysctls. Both +modifications are turned off by default. + +References +========== +More information on the modifications, as well as a wide range of +experimental data can be found here: + +"Improving latency for interactive, thin-stream applications over +reliable transport" +http://simula.no/research/nd/publications/Simula.nd.477/simula_pdf_file diff --git a/Documentation/networking/tcp-thin.txt b/Documentation/networking/tcp-thin.txt deleted file mode 100644 index 151e229980f1..000000000000 --- a/Documentation/networking/tcp-thin.txt +++ /dev/null @@ -1,47 +0,0 @@ -Thin-streams and TCP -==================== -A wide range of Internet-based services that use reliable transport -protocols display what we call thin-stream properties. This means -that the application sends data with such a low rate that the -retransmission mechanisms of the transport protocol are not fully -effective. In time-dependent scenarios (like online games, control -systems, stock trading etc.) where the user experience depends -on the data delivery latency, packet loss can be devastating for -the service quality. Extreme latencies are caused by TCP's -dependency on the arrival of new data from the application to trigger -retransmissions effectively through fast retransmit instead of -waiting for long timeouts. - -After analysing a large number of time-dependent interactive -applications, we have seen that they often produce thin streams -and also stay with this traffic pattern throughout its entire -lifespan. The combination of time-dependency and the fact that the -streams provoke high latencies when using TCP is unfortunate. - -In order to reduce application-layer latency when packets are lost, -a set of mechanisms has been made, which address these latency issues -for thin streams. In short, if the kernel detects a thin stream, -the retransmission mechanisms are modified in the following manner: - -1) If the stream is thin, fast retransmit on the first dupACK. -2) If the stream is thin, do not apply exponential backoff. - -These enhancements are applied only if the stream is detected as -thin. This is accomplished by defining a threshold for the number -of packets in flight. If there are less than 4 packets in flight, -fast retransmissions can not be triggered, and the stream is prone -to experience high retransmission latencies. - -Since these mechanisms are targeted at time-dependent applications, -they must be specifically activated by the application using the -TCP_THIN_LINEAR_TIMEOUTS and TCP_THIN_DUPACK IOCTLS or the -tcp_thin_linear_timeouts and tcp_thin_dupack sysctls. Both -modifications are turned off by default. - -References -========== -More information on the modifications, as well as a wide range of -experimental data can be found here: -"Improving latency for interactive, thin-stream applications over -reliable transport" -http://simula.no/research/nd/publications/Simula.nd.477/simula_pdf_file