[LARTC] Explanation reqd. for few (more than few!) concepts in TC <long>

From: Suraj Shankar <su_raj_in@yahoo.com>
To: lartc@vger.kernel.org
Subject: [LARTC] Explanation reqd. for few (more than few!) concepts in TC <long>
Date: Tue, 28 Oct 2003 07:06:00 +0000	[thread overview]
Message-ID: <marc-lartc-106732522922215@msgid-missing> (raw)

Hi all,
  I am a system administrator trying to understand tc.
I have been following the lartc documentation along
with a few others. I am unable to understand few
things explained in the howtos. Kindly help me with
the same ...
1) Can somebody tell me the exact difference between a
class and a qdisc? Martin Brown did try to explain to
me but, I couldn't understand!
2) When we talk about pfifo, what is the 'pack size'
understood to be; example, when I set limit to 10
(packets), how many bytes is my bucket?
3) 'HTB is suited for fixed bandwidth' ... by "fixed"
what exactly is meant ... meaning can it be used where
bandwidth is shared but at almost always a certain
"fixed" bandwidth is available (even if available
bandwidth exceeds, it will be by only a few bytes, for
a short duration)?
4) Can somebody suggest which qdisc is most ideal (for
shaping and scheduling) in a n/w where the ISP provies
a (512Kbit) pipe, which is shared by multiple (4)
clients but, an average of 45bytes can be expected at
any point in time (although, it might exceed this)?
5) The lartc howto speaks about 'mpu' with reference
to TBF, and states "for ethernet, no packet uses less
than 64 bytes", can you please tell me whether 64
bytes is the least possible; meaning adding 20 bytes
of IP and 28 bytes of TCP, I believed a TCP/IP packet
with no payload could exist of 48 bytes, is this
possible? and if a payload must be added, should it be
16 bytes atleast, can I not have a 52 byte ethernet
packet? Kindly explain.
Also, I am unable to see such a parameter when I do a
tc...help, for TBF.
6) Could you please define the 'cell' parameter in a
CBQ?
Also, I am unable to see maxburst, minburst, minidle,
mpu, rate parameter options when I do a ... for ex. :
'tc qdisc add dev eth0 handle 1 root cbq help'
7) How do I set WRR, link sharing and borrowing
parameters using TC?
8) Also, please pardon my ignorance but, do I need a
filter for a classless qdisc, cause if I were to
attach a classless qdisc to the root qdisc then by
default all packets enter this qdisc and I believe I
wouldn't have the scope to classify ... right/wrong?

  Please help me.
   Thank you.

Regards,
suraj.

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