[Asterisk-Users] g729 and latency measures

[Erick Perez]

Thanks Rich, but i'm only allowed to use g729.
you said that some folks run high latency connections, but is 300ms
high in my setup?

On 3/19/06, Rich Adamson <radamson at routers.com> wrote:
> Erick Perez wrote:
> > Hi, we have set up a small project in a school the following way:
> > SITE_A(4 port analog to ip
> > g729)------ADSL_ISP1-------ISP2--------Asterisk-----PSTN
> > Site A has 1 Megabit of bandwith (up 512kilobit down 1 megabit)
> > The asterisk box gets internet service via a wireless antenna. 1 Mbit
> > of up/down bandwith
> >
> > Comments:
> > So far, this means that I will need licenses for the 729.
> > asterisk only supports 20ms sampling on g729 so 4 channels will need
> > 96 kilobits at 20ms sampling (or is it kilobytes??) for the internet
> > bandwith.
> > i cannot use CRTP because i cant be sure if the ISP's routers are CRTP aware.
> > Installing ADSL from ISP1 on the asterisk place will give a clear advantage
> >
> > Please correct any of my prior statements if wrong.
> >
> > should I maintain packet latency below 300ms or 150ms?
>
> The objective should be to keep latency as low as possible, however some
> folks do run asterisk via satellite which as a very lengthy latency.
>
> > How can I measure this latency all the way to the asterisk?
>
> Several ways depending on how accurate a measurement you want. A simple
> ping would give a starting point. A much more expensive way is to use
> VoIP analysis software to measure it, but be prepared to spend at least
> $1,500 (US) to do that.
>
> > Should I ping from SITE_A to the asterisk box with 8k packets?
>
> If you want to emulate a sip/iax packet, use a packet size of about 200
> bytes.
>
> > If I can't install ADSL for the moment, will the above setup work?
>
> Probably a bigger issue to address relates to what "other" traffic might
> be passing across the dsl and/or wireless channel that might be
> consuming bandwidth and impacting the rtp packets.  Broadcasts
> originating from devices outside your control (other isp users), hackers
> attempting to access your ip addresses (at both ends), data traffic
> between your two endpoints, etc, are just some thoughts of items using a
> portion of the bandwidth available.
>
> Might also think about jitter (eg, variations in latency) and what that
> might do to your end to end communications.
>
> There are other low bandwidth codecs available that could be used
> instead of g729. Some include ilbc, g726, gsm, etc. Each consumes
> different bandwidths, and each provide a slightly different quality of
> audio. See the wiki for more detail on what each consumes for bandwidth
> on the wire.
>
>
>
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--

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Erick Perez
Linux User 376588
http://counter.li.org/  (Get counted!!!)
Panama, Republic of Panama