[LARTC] [patch] Improvements for the TBF chapter

[Christian Hammers <ch@westend.com>]

Hi

Please consider applying this patch:
	- Clearifies the relation between 'rate' and 'burst'
	- Corrects statement about non-existing input qdisc (-> IMQ)

bye,

-christian-

Index: lartc.db
=================================RCS file: /var/cvsroot/2.4routing/lartc.db,v
retrieving revision 1.12
diff -u -B -b -r1.12 lartc.db
--- lartc.db	20 Jul 2002 14:44:26 -0000	1.12
+++ lartc.db	28 Jul 2002 11:25:06 -0000
@@ -2102,18 +2102,27 @@
 </Para>
 </VarListEntry>
 <VarListEntry>
-<Term>burst/buffer/maxburst</Term>
+<Term>rate and burst/buffer/maxburst</Term>
 <ListItem>
 <Para>
-Size of the bucket, in bytes. This is the maximum amount of bytes that
-tokens can be available for instantaneously. In general, larger shaping
-rates require a larger buffer. For 10mbit/s on Intel, you need at least
-10kbyte buffer if you want to reach your configured rate!
+Rate is the amount of tokens that are tried to put into the bucket every 
+second specified in mbit/s.
+</Para>
+<Para>
+Burst is the size of the bucket, in bytes. This is the maximum amount of bytes
+that tokens can be available for instantaneously.
 </Para>
-
 <Para>
-If your buffer is too small, packets may be dropped because more tokens
-arrive per timer tick than fit in your bucket.
+In general, larger shaping rates require a larger buffer. Remember that if
+your buffer is too small, packets may be dropped because regardless how
+much tokens the 'rate' parameter tries to put in the bucket, the ones that
+actually fit into it are not sufficient for all waiting data.
+</Para>
+<Para>To archive a throughput of 10mbit/s on Intel you have to set the buffer
+to 12.8kbyte. Calculation: On Intel the kernel HZ variable is 100, which means
+that the token filler function is called 100 times per second. 100 times 
+12.8kbyte are 1310720byte or 10485760bit that are pushed into the bucket - 
+assuming a high enough value for the rate variable.
 </Para>
 </VarListEntry>
 <VarListEntry>
@@ -2125,13 +2134,6 @@
 token usage for a packet.
 </Para>
 </VarListEntry>
-<VarListEntry>
-<Term>rate</Term>
-<ListItem>
-<Para>
-The speedknob. See remarks above about limits!
-</Para>
-</VarListEntry>
 </VariableList>
 </Para>
 
@@ -2502,8 +2504,10 @@
 <ListItem>
 <Para>
 Delaying or dropping packets in order to make traffic stay below a
-configured bandwidth. In Linux, policing can only drop a packet and not
-delay it - there is no 'ingress queue'.
+configured bandwidth. In Linux, policing used to be only able to drop a packet
+and not delay it - there was no 'ingress queue'. A currently developed solution
+is the 'intermediate queueing device' (IMQ). It is discussed in a seperate
+chapter. 
 </Para>
 </VarListEntry>
 <VarListEntry>

-- 
Christian Hammers    WESTEND GmbH - Aachen und Dueren     Tel 0241/701333-0
ch@westend.com     Internet & Security for Professionals    Fax 0241/911879
          WESTEND ist CISCO Systems Partner - Authorized Reseller

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