netdev - [PATCH iproute2 4/4] netem: add documentation for the new slotting feature

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Message-Id: <1510089416-5945-5-git-send-email-dave.taht@gmail.com>
Date:   Tue,  7 Nov 2017 13:16:56 -0800
From:   Dave Taht <dave.taht@...il.com>
To:     netdev@...r.kernel.org
Cc:     Dave Taht <dave.taht@...il.com>
Subject: [PATCH iproute2 4/4] netem: add documentation for the new slotting feature

Signed-off-by: Dave Taht <dave.taht@...il.com>
---
 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