From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Taht Subject: [PATCH iproute2 4/4] netem: add documentation for the new slotting feature Date: Tue, 7 Nov 2017 13:16:56 -0800 Message-ID: <1510089416-5945-5-git-send-email-dave.taht@gmail.com> References: <1510089416-5945-1-git-send-email-dave.taht@gmail.com> Cc: Dave Taht To: netdev@vger.kernel.org Return-path: Received: from mail-pf0-f194.google.com ([209.85.192.194]:46182 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933968AbdKGVRG (ORCPT ); Tue, 7 Nov 2017 16:17:06 -0500 Received: by mail-pf0-f194.google.com with SMTP id p87so426830pfj.3 for ; Tue, 07 Nov 2017 13:17:06 -0800 (PST) In-Reply-To: <1510089416-5945-1-git-send-email-dave.taht@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Signed-off-by: Dave Taht --- man/man8/tc-netem.8 | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) diff --git a/man/man8/tc-netem.8 b/man/man8/tc-netem.8 index b31384f..8c41d77 100644 --- a/man/man8/tc-netem.8 +++ b/man/man8/tc-netem.8 @@ -8,7 +8,8 @@ NetEm \- Network Emulator .I OPTIONS .IR OPTIONS " := [ " LIMIT " ] [ " DELAY " ] [ " LOSS \ -" ] [ " CORRUPT " ] [ " DUPLICATION " ] [ " REORDERING " ][ " RATE " ]" +" ] [ " CORRUPT " ] [ " DUPLICATION " ] [ " REORDERING " ] [ " RATE \ +" ] [ " SLOT " ]" .IR LIMIT " := " .B limit @@ -51,6 +52,14 @@ NetEm \- Network Emulator .B rate .IR RATE " [ " PACKETOVERHEAD " [ " CELLSIZE " [ " CELLOVERHEAD " ]]]]" +.IR SLOT " := " +.BR slot +.IR MIN_DELAY " [ " MAX_DELAY " ] {[" +.BR packets +.IR PACKETS " ] [ " +.BR bytes +.IR BYTES " ] }]" + .SH DESCRIPTION NetEm is an enhancement of the Linux traffic control facilities @@ -162,6 +171,27 @@ granularity avoid a perfect shaping at a specific level. This will show up in an artificial packet compression (bursts). Another influence factor are network adapter buffers which can also add artificial delay. +.SS slot +defer delivering accumulated packets to within a slot, with each available slot +configured with a minimum delay to acquire, and an optional maximum delay. Slot +delays can be specified in nanoseconds, microseconds, milliseconds or seconds +(e.g. 800us). Values for the optional parameters +.I BYTES +will limit the number of bytes delivered per slot, and/or +.I PACKETS +will limit the number of packets delivered per slot. + +These slot options can provide a crude approximation of bursty MACs such as +DOCSIS, WiFi, and LTE. + +Note that slotting is limited by several factors: the kernel clock granularity, +as with a rate, and attempts to deliver many packets within a slot will be +smeared by the timer resolution, and by the underlying native bandwidth also. + +It is possible to combine slotting with a rate, in which case complex behaviors +where either the rate, or the slot limits on bytes or packets per slot, govern +the actual delivered rate. + .SH LIMITATIONS The main known limitation of Netem are related to timer granularity, since Linux is not a real-time operating system. -- 2.7.4