[VoiceOps] VoIP over 3G/4G Data Connection

Colton Conor colton.conor at gmail.com
Sun Jul 27 14:14:38 EDT 2014

Alright notes taken so far is to obtain a static IP with the wireless
carrier to avoid their Carrier Grade NAT. We already paid $500 to get
static IPs from Verizon, so we are good to go there.

In addition use TCP for SIP. I believe we already use TCP for the SIP
signaling as we use the TCPpreferred setting on the Polycom VVX line, and
our service provider supports TCP with their Acme Packet / Broadsoft setup.
Just the signaling is TCP right? The RTP media is still UPD I assume?

Of course we would like to use a wideband codec, but I have
heard narrowband codecs work better due to less data traffic (which as you
know data is expensive on wireless). Looks like G.729 and iLBC are the most
supported narrowband codecs today. What are the thoughts about both of
these codecs? Which is better? I assume the session border controller or
softswitch would transcode the call to G.711 to send it out over the PSTN,
so do either of these codecs transcode or sound better when converted to
G.711? Are there any other codecs besides these two?

I assume we are going to be dealing with alot of packet loss whether its
going to 3G or 4G. We are also going to be dealing with high latency on 3G.
Since we have no control over both of these issues, what other
recommendations do you have? I have heard changing the ptime can help,
and certain codes have different ptime settings. I have also read about
trying to keep the MTU size down, and using SIP header compression helps. I
don't know much about this.

Any more advice would be appreciated.

On Fri, Jul 25, 2014 at 2:50 PM, Alex Balashov <abalashov at evaristesys.com>

> +1 on using TCP for traversing many layers of NAT of varying quality +
> getting around the infantile thumb-sucking that passes for ALG-"assisted"
> NAT traversal.
> --
> Alex Balashov - Principal
> Evariste Systems LLC
> Tel: +1-678-954-0670
> Web: http://www.evaristesys.com/, http://www.alexbalashov.com/
> Please be kind to the English language:
> http://www.entrepreneur.com/article/232906
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