[LARTC] (yet another) HTB question(s)

[LARTC] (yet another) HTB question(s)

[Gabriel]

Hi, I've read the documentation about HTB and I pretty much
managed to grasp how it works. In theory. But there still
are some questions and I want to check with you to see if I
understand things correctly. So here goes:
1) when used on a router for shaping traffic done by
clients connected to it, shaping is done on the interface
connected to the cable/dsl modem. If I wanted to create
classes for every client on the network, I would have to
use iptables to mark packets (using -j MARK) and not
filters because, according to
http://www.docum.org/docum.org/kptd/ the shaping is done
after the SNAT, so all the clients would have the src
address rewritten with the public IP. Am I getting this
right?
2) shaping inbound traffic is tricky because you can't
control the rate that the packets come to you. Is it a good
idea to shape the outgoing traffic to the clients on the
LAN side NIC? Would I achieve both upload and download
shaping using the same htb script (a script that does
shaping using iptables for marking packets and fw for
matching them) on both NICs (LAN side and ISP side)?
3) I've tried to find an answer to this question but all I
got was some similar question a couple of years ago from
Martin Brown. What happens if shaping a variable bandwidth
link and, at one moment, for a period of time, the
available bandwidth goes beyond the rate specified for the
class 1:1 (the class attached to the root qdisc)? How will
htb act in such a situation?
4) related to 3), I've tried to use a syntax like this: "tc
clas add dev $ETH parent 1:0 classid 1:1 htb rate $RATE
ceil $CEIL", where CEIL > RATE , but the  max speed I
achieved was the RATE speed. After further reading, I found
out that you can't (well, you can, there's no syntax error,
but it's useless) specify CEIL for the class attached to
the root qdisc because it doesn't have a parent to borrow
from. So is there a way to simulate a variable bandwidth
link or should I just set RATE to the highest possible
value the bandwidth can reach?
5) related to 1). Is there a (major) difference between -j
MARK and -j CLASSIFY? From what I've read, -j CLASSIFY sets
both the major and minor (major:minor) numbers to be
matched while -j MARK only sets the minor.

That's about it for now. :) Thanks


		
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Re: [LARTC] (yet another) HTB question(s)

[Andreas Klauer]

On Tuesday 16 August 2005 21:37, Gabriel wrote:
> If I wanted to create classes for every client on the network, I would
> have to use iptables to mark packets (using -j MARK) and not
> filters because, according to 
> http://www.docum.org/docum.org/kptd/ the shaping is done
> after the SNAT, so all the clients would have the src
> address rewritten with the public IP. Am I getting this
> right?

I'm not 100% sure, but I think so. Anyway, I'm more comfortable with 
iptables than the sometimes rather complicated tc filter syntax. So I try 
to do most stuff in iptables.

> 2) shaping inbound traffic is tricky because you can't
> control the rate that the packets come to you. Is it a good
> idea to shape the outgoing traffic to the clients on the
> LAN side NIC?

Yes, you can't control the way packets come to you directly. But still, 
does that mean you should allow an incoming connection to hog the whole 
bandwidth? Dropping packets slows down incoming tcp connections, and in my 
case, although dropping means throwing away already-downloaded packets, I 
feel it improved usability.

> Would I achieve both upload and download shaping using the same htb
> script (a script that does shaping using iptables for marking packets and
> fw for matching them) on both NICs (LAN side and ISP side)?

There might be minor differences (on LAN interface, you have to account for 
internal LAN traffic, e.g. SSH sessions to your router, and other local 
services you might be running, which do not actually use internet 
bandwidth.

> What happens if shaping a variable bandwidth link and, at one moment, for
> a period of time, the available bandwidth goes beyond the rate specified
> for the class 1:1 (the class attached to the root qdisc)? How will
> htb act in such a situation?

I don't have a variable bandwidth link, but I guess HTB won't let you use 
more bandwith than specified in any case.

> 4) related to 3), I've tried to use a syntax like this: "tc
> clas add dev $ETH parent 1:0 classid 1:1 htb rate $RATE
> ceil $CEIL", where CEIL > RATE , but the  max speed I
> achieved was the RATE speed. After further reading, I found
> out that you can't (well, you can, there's no syntax error,
> but it's useless) specify CEIL for the class attached to
> the root qdisc because it doesn't have a parent to borrow
> from. So is there a way to simulate a variable bandwidth
> link or should I just set RATE to the highest possible
> value the bandwidth can reach?

I doubt that HTB was made for variable bandwidth links. Anyway, I suggest 
you try out both possibilities and use the ones that work best for you. 
Shaping is always a lot of trial & error in my opinion.

> 5) related to 1). Is there a (major) difference between -j
> MARK and -j CLASSIFY? From what I've read, -j CLASSIFY sets
> both the major and minor (major:minor) numbers to be
> matched while -j MARK only sets the minor.

I haven't used classify so far, but if I understand it right, it puts 
packets directly into the appropriate class. If that's true, it's a good 
idea to use it, since it saves you the hassle of first marking packets and 
then adding tc filter matches for that mark.

HTH
Andreas
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Re: [LARTC] (yet another) HTB question(s)

[Dmytro O. Redchuk]

On Tue, Aug 16, 2005 at 12:37:48PM -0700, Gabriel wrote:
> 1) when used on a router for shaping traffic done by
> clients connected to it, shaping is done on the interface
> connected to the cable/dsl modem. If I wanted to create
> classes for every client on the network, I would have to
> use iptables to mark packets (using -j MARK) and not
> filters because, according to
> http://www.docum.org/docum.org/kptd/ the shaping is done
> after the SNAT, so all the clients would have the src
> address rewritten with the public IP. Am I getting this
> right?
This page:
http://mailman.ds9a.nl/pipermail/lartc/2005q1/014656.html
(LARTC archive) contains a lot of useful links, one of them:
http://ebtables.sourceforge.net/br_fw_ia/PacketFlow.png

Note right bottom corner of that picture.

> 4) related to 3), I've tried to use a syntax like this: "tc
> clas add dev $ETH parent 1:0 classid 1:1 htb rate $RATE
> ceil $CEIL", where CEIL > RATE , but the  max speed I
> achieved was the RATE speed. After further reading, I found
> out that you can't (well, you can, there's no syntax error,
> but it's useless) specify CEIL for the class attached to
> the root qdisc because it doesn't have a parent to borrow
> from. So is there a way to simulate a variable bandwidth
> link or should I just set RATE to the highest possible
> value the bandwidth can reach?
http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm (6. Priorizing
bandwidth share) answers this question. Use qdisc inside qdisc.

> That's about it for now. :) Thanks
Thank you,

-- 
  _,-=._              /|_/|
  `-.}   `=._,.-=-._.,  @ @._,
     `._ _,-.   )      _,.-'
        `    G.m-"^m`m'        Dmytro O. Redchuk

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Re: [LARTC] (yet another) HTB question(s)

[panca sorin]

> 4) related to 3), I've tried to use a syntax like
this: > "tc
> clas add dev $ETH parent 1:0 classid 1:1 htb rate
$RATE
> ceil $CEIL", where CEIL > RATE , but the  max speed
I
> achieved was the RATE speed.

try to add 2-level root class:
tc qdisc add dev $ETH root handle 1: htb default FF
tc class add dev $ETH parent 1: classid 1:1 htb rate
$MAXRATE ceil $MAXRATE
tc class add dev $ETH parent 1:1 classid 1:2 htb rate
$MINRATE ceil $MAXRATE
tc class add ... [your child classes]

I don't know if it'll work but worth trying.


		
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