[LARTC] newbie - shaping a PSTN connection

[LARTC] newbie - shaping a PSTN connection

[Daniel Horth]

Hi - I've been going through the LARTC how-to and have successfully used the
sample scripts (and wondershaper) with my xDSL links.

I'm now faced with the challenge of providing 8 users at work an effective
remote access connection over a PSTN ppp connection. The critical traffic in
this case relates to our stock enquiry application which is running over
terminal services.

I've been attempting to use the wondershaper script with this PSTN
connection - but don't seem to be able to improve latency at all. doing a
bit of research I've only really found references to shaping broadband
connections. Surely shaping of PSTN ppp connections is equally (probably
more) applicable?

I was hoping that someone might be able to point me in the direction of
information relating to successfully providing my users high priority
terminal services traffic over the PSTN link.

I would also appreciate being shown where I might find a searchable archive
of this list.

Thanks in advance!

- Dan.

PS. in case you think I'm mad running 8 users over PSTN - it's just a
stop-gap while we wait for our SHDSL installations - which should be in by
the end of the month. In future I will be using the PSTN as a backup incase
the SHDSL goes down though - so any shaping work will not be lost!

__________________________________
Euroluce Lighting Australia PTY LTD
92-94 Tennyson Road, Mortlake, NSW 2137
Ph: (02) 9743 6099   Fx: (02) 9743 6406
http://www.euroluce.com.au/

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Re: [LARTC] newbie - shaping a PSTN connection

[Damion de Soto]

Daniel Horth wrote:
> Hi - I've been going through the LARTC how-to and have successfully used the
> sample scripts (and wondershaper) with my xDSL links.
Are you using the cbq or htb shaping scripts ?

> I've been attempting to use the wondershaper script with this PSTN
> connection - but don't seem to be able to improve latency at all. doing a
> bit of research I've only really found references to shaping broadband
> connections. Surely shaping of PSTN ppp connections is equally (probably
> more) applicable?
If you're using low bandwidth values with the htb qdisc, you might have to change the
r2q parameter - see http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm


> I would also appreciate being shown where I might find a searchable archive
> of this list.
just use google on http://mailman.ds9a.nl/pipermail/lartc/


regards

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Damion de Soto - Software Engineer  email:     damion@snapgear.com
SnapGear ---                           ph:         +61 7 3435 2809
  | Custom Embedded Solutions          fax:         +61 7 3891 3630
  | and Security Appliances            web: http://www.snapgear.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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RE: [LARTC] newbie - shaping a PSTN connection

[Dancer Vesperman]

No worries. Why does it work?
Every packet leaving an interface is up to MTU bytes in length. Let's
say that a byte is ten bits (8+ 1start+1stop). So a 1500byte packet is
15000 bits. On a 28.8K connection, that means a 1500 byte packet takes
0.52 seconds to transmit. Assuming that the queueing discipline is FIFO
(first-in-first out) and the queue length on the interface is, say, 10
packets, a packet can take 10*0.52 seconds to get to the head of the
queue. Plus transmission time, that's 5.2 (for queuing) +0.52 for
transmission. Quite a delay.

You may be able to do better by shortening the packet queue on the
interface (ip link set ppp0 qlen 4) for example. Or attaching an SFQ
queueing discipline (tc qdisc add dev ppp0 root handle 1: sfq perturb
10) - although for SFQ, I think you'd want a more substantive queue
length.


On Tue, 2003-09-09 at 18:52, Daniel Horth wrote:
> wow - from 8 second ping responses on my heavily loaded link to 2 second
> just by changing the MTU - sure I'll be able to improve further on that with
> experimentation.
> 
> thanks for that!
> 
> - dan.
> 
> 
> -----Original Message-----
> From: Dancer Vesperman [mailto:dancer@anthill.echidna.id.au]
> Sent: Tuesday, 9 September 2003 6:37 PM
> To: Daniel Horth
> Subject: Re: [LARTC] newbie - shaping a PSTN connection
> 
> 
> I'd seriously advise cutting your MTU/MRU down. A lot. Say as low as 562
> or 168. If your MTU/MRU is defaulting to 1500, it's going to be hard to
> get any effective shaping on your link.
> 
> On Tue, 2003-09-09 at 18:21, Daniel Horth wrote:
> > Hi - I've been going through the LARTC how-to and have successfully used
> the
> > sample scripts (and wondershaper) with my xDSL links.
> 
> __________________________________
> Euroluce Lighting Australia PTY LTD
> 92-94 Tennyson Road, Mortlake, NSW 2137
> Ph: (02) 9743 6099   Fx: (02) 9743 6406
> http://www.euroluce.com.au/
> 
> The contents of this email are confidential. If you are not, or believe you
> may not be, the intended recipient of this email, please let us know by
> reply and then delete it from your system. You should not copy the message
> or disclose its contents to anyone. No warranty or other assurance is given
> by us that this email is free of any virus or any other defect or error.
> 
> Any views or opinions presented in this email are solely those of the author
> and do not necessarily represent those of the company. If verification is
> required please request a hard-copy version.
> 
> Scanned by Inflex - Queries to: postmaster@euroluce.com.au
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Re: [LARTC] newbie - shaping a PSTN connection

[Dan Horth]

Damion de Soto said:
> Daniel Horth wrote:
>> Hi - I've been going through the LARTC how-to and have successfully
used
>> the
>> sample scripts (and wondershaper) with my xDSL links.
> Are you using the cbq or htb shaping scripts ?

The cbq scripts...

>> I've been attempting to use the wondershaper script with this PSTN
connection - but don't seem to be able to improve latency at all. doing
a
>> bit of research I've only really found references to shaping broadband
connections. Surely shaping of PSTN ppp connections is equally
(probably
>> more) applicable?
> If you're using low bandwidth values with the htb qdisc, you might have
to
> change the
> r2q parameter - see http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm

I guess I need to do further reading on this - I was confused and thought
that the htb script involved a different software set and as such I opted
for the working cbq script. Anyway - The site you pointed at seems to have
a good amount of interesting information - I'll have a good read through
that before I post further questions!

>> I would also appreciate being shown where I might find a searchable
archive
>> of this list.
> just use google on http://mailman.ds9a.nl/pipermail/lartc/

that's what I tried first before posting any questions - but google don't
have that URL indexed... then I worked out that with searching within a
site using google it needs to be the top domain, not the full URL, ie:

shape ppp site:http://mailman.ds9a.nl/pipermail/lartc/

does not work, but:

shape ppp site:http://mailman.ds9a.nl

does... anyway - I digress, this is not a "how-to search using google"
list after all! :)

thanks for the pointers, I'll be dropping by the list again once I've done
a bit more research!

- Dan.
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Re: [LARTC] newbie - shaping a PSTN connection

[Stef Coene]

On Wednesday 10 September 2003 02:43, Dancer Vesperman wrote:
> No worries. Why does it work?
> Every packet leaving an interface is up to MTU bytes in length. Let's
> say that a byte is ten bits (8+ 1start+1stop). So a 1500byte packet is
> 15000 bits. On a 28.8K connection, that means a 1500 byte packet takes
> 0.52 seconds to transmit. Assuming that the queueing discipline is FIFO
> (first-in-first out) and the queue length on the interface is, say, 10
> packets, a packet can take 10*0.52 seconds to get to the head of the
> queue. Plus transmission time, that's 5.2 (for queuing) +0.52 for
> transmission. Quite a delay.
>
> You may be able to do better by shortening the packet queue on the
> interface (ip link set ppp0 qlen 4) for example. Or attaching an SFQ
> queueing discipline (tc qdisc add dev ppp0 root handle 1: sfq perturb
> 10) - although for SFQ, I think you'd want a more substantive queue
> length.
You can use sfq with a shorter queue :
http://www.docum.org/stef.coene/qos/faq/cache/21.html

Stef

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 "Using Linux as bandwidth manager"
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     #lartc @ irc.oftc.net

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Re: [LARTC] newbie - shaping a PSTN connection

[Stef Coene]

On Wednesday 10 September 2003 01:44, Damion de Soto wrote:
> Daniel Horth wrote:
> > Hi - I've been going through the LARTC how-to and have successfully used
> > the sample scripts (and wondershaper) with my xDSL links.
>
> Are you using the cbq or htb shaping scripts ?
>
> > I've been attempting to use the wondershaper script with this PSTN
> > connection - but don't seem to be able to improve latency at all. doing a
> > bit of research I've only really found references to shaping broadband
> > connections. Surely shaping of PSTN ppp connections is equally (probably
> > more) applicable?
>
> If you're using low bandwidth values with the htb qdisc, you might have to
> change the r2q parameter - see
> http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm
And I also have to promote my site a bit :)
http://docum.org

Stef

-- 

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 "Using Linux as bandwidth manager"
     http://www.docum.org/
     #lartc @ irc.oftc.net

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