Encrypted mobile to landline phone calls with Asterisk 1.8, Snom ...

Disable TCP keepalive
Most modern operating system support TCP keepalive at Layer3 of ISO/OSI pile.
The TCP keepalive of Linux must be disabled because the TCP keepalive to keep the TLS connection is done at SIP protocol
level by PrivateGSM Enterprise that every 3 minutes send a \r\n to the SIP/TLS server (56byte of data).
On Linux you can disable TCP keepalive with the following command:
● echo 0 > /proc/sys/net/ipv4/tcp_keepalive_probes
Choose right data plan
In order to use mobile VoIP networking efficiently you must consider
Think that on mobile networks with:
● AMR 4.75kbit you consume about 100Kbyte/s per minute
● AMR 12.2kbit you consume about 200Kbyte/s per minute
Additionally PrivateGSM require an always-on connection that consume 1-2Mb/months to keep connection to PBX always on.
Best data plans are:
● Flat
● Traffic based
You must not use a time based mobile data plan.
Example SIP account
In this section you will find example extension (VoIP account) with the specific configuration parameters required to configure a
PrivateGSM Enterprise and a Snom phone.
The extension has to be put in sip.conf or in realtime sql configuration.
PrivateGSM SIP account
Below is reported an example for SIP account for a PrivateGSM Enterprise phone.
Here we add only the required field that must be used for Private GMS Enterprise edition.
disallow=all
allow=amr:100
autoframing=yes
encryption=yes
transport=tls
port=5061
qualify=no
Snom SIP account
Below is reported an example for SIP account for a Snom phone:
disallow=all
allow=gsm
autoframing=yes
encryption=yes
transport=tls
port=5061
qualify=yes