[Asterisk-Users] (newby) IAX Trunk on low bandwidth connection

Thu Feb 2 04:30:33 MST 2006

At my HQ I'm instaling a 128kbit leased line connection, with guaranteed
bandwidth to the Internet; The telco promises less then 20 ms to the
internet (to ronix.ro), no jitter and no packet loss. So I'm hoping for 40
ms times to net and small jitter :-) This is my "hub".

For my "satelite" instalations I'm planning on grabing a connection from a
different provider (as this telco provider is expensive) but I'm also
considering a 64kbit leased line from the same provider, just in case my
VoIP doesn't work with the cheeper providers. My remote instalations will
never have more then one "conversation" load, and this conversation would be
ZAP to IAX or SIP. That is, the distant instalation will need to forward all
calls coming in on the zap chanel to my HQ Asterisk. That's all it will ever
do :-). I'm not sure "trunking" woud provide anything in this case as there
will never be more then one concurent conversation from the remote * to my
HQ *. I'm expecting IAX to provide better performance over SIP but not by
much. 

Considering my remote * instalations will never have more then one concurent
conversation with my HQ and considering I can get a really good 64kbit line
I guess I'm OK. As for my HQ, I'm sure I'm OK because I'll get a 128 kbit
line and I'll be able to afford an upgrade to 256kbit. I can actually go all
the way to 2048 kbit, but that would no longer be economically viable.

So I'll see how it goes, and I hope I'll have the time to put in a comment
on the "low bandwidth" wiki on voip-info.org.

Thanks to everyone for your help.

  _____  

From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of tim panton
Sent: Thursday, February 02, 2006 11:05 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] (newby) IAX Trunk on low bandwidth connection

On 2 Feb 2006, at 08:09, Cosmin Prund wrote:

Brrghhh: Bandwidth calculation is really foggy for me:

Using the calculator I'm getting about 23 kbps for both incoming and
outgoing. What does this mean: Is a 64kbit link used at 71% capacity
((23+23):64) or is it used at only 35% (23:64)? Will this vary over time
(i.e: does the codec generate more then average data at times? How about
less then average?)

It depends on what sort of link you have. Most links are full duplex (leased
lines etc) which would be 35%

but some radio based links are half duplex which would be 71%

So for a 64k link you will (just about) get 3 729 calls. 

If all the calls between are between the same two servers, you can use IAX
trunking, which would push

you up to 5 calls. (What that tells you is that for 729 and gsm, the headers
are as big as the data).

You talk about satellite stations, if you are going for a hub and spoke, you
should put the hub

on the highest bandwidth link. 

Thanks. 

  _____  

From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Rob Lith
Sent: Wednesday, February 01, 2006 11:40 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] (newby) IAX Trunk on low bandwidth connection

What codec is that using. G.729 will give you 10 calls at best over 256k
unless you're trunking with IAX2? I don't know anyone using lpc10...

Remember a G.729 8k codec turns into 23.63 Kbps with all the overheads... 

Regards
Rob

On 2/1/06, Garth van Sittert <garth at bitco.co.za> wrote:

Hi Cosmin

You should be able to get about 12 simultaneous calls on a 128k line and
about 28 on a 256k line according to asteriskguru's bandwidth calculator
http://www.asteriskguru.com/tools/bandwidth_calculator.php.

Kind Regards
Garth

BitCo Data Communications
http://www.bitco.co.za

Cosmin Prund wrote:
> Hello everyone, this is my first post to the list, so hello again. 
>
> We're a small company in Romania and we're trying to set up a really small
> version of "call center". That is, we want to get a few land-lines from
our
> telco in different countys and "bridge" all calls to our HQ, in order to 
> make it cheeper for our clients to call us.
>
> Unfortunatelly there's no ISP in our area that can deliver a broadband
> connection for anything less then an arm and a leg, so we're considering
> runing an * <-> * connection using VoIP over a low bandwidth connection
> (we're considering 128kbit but we might be able to go to 256kbit).
>
> The bandwidth price is not a problem for our "satelite" installations, we 
> cand get acceptably priced broadband (~256kbit) so the distant *'s will
have
> propper connections.
>
> My question:
>
> Is 128kbit a wide enough connection for 1 simultaneous conversation, using

> IAX protocol with the comercial version of the g729 codec?
>
> I'm expecting this to be engough for more then 1 conversation (after all a
> single line analog connection is rated at 64kbit and I'm getting double
that 
> bandwidth)
>
> Cosmin Prund
>
>
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>

--
Garth van Sittert
BSc (Physics & Computer Science)
-----------------
Mobile: +27 (0)83 791 6662
Email:  garth at bitco.co.za 
Phone:  08600 BITCO
Web:    www.bitco.co.za

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