System information

VoIP to VoIP
Eventually, the need for the PSTN will likely vanish, and most voice communications
will take place over network connections.
The original thinking behind the SIP protocol was that it was to be a peer-to-peer
protocol. Technically, this is still the case. What has happened, however, is that things
have gotten a bit more complicated. Issues such as security, privacy, corporate policies,
integration, centralization, and so forth have made things a bit more involved than
simply putting a URI into a SIP phone and having a SIP phone somewhere else ring in
response.
The SIP protocol has become bloated and complex. Implementing SIP-based systems
and networks has arguably become even more complicated than implementing tradi-
tional phone PBXs and networks.
#
We are not going to get into the complexities of designing and implementing VoIP
networks in this book, but we will discuss some of the ways you can configure Asterisk
to support VoIP connectivity to other VoIP systems.
Configuring VoIP Trunks
In Asterisk, there is no need to explicitly install your VoIP modules (unless for some
reason you did not compile Asterisk with the required modules). There are several VoIP
protocols that you can choose to use with Asterisk, but we will focus on the two most
popular: SIP and IAX.
Configuring SIP trunks between Asterisk systems
SIP is far and away the most popular of the VoIP protocols—so much so that many
people would consider other VoIP protocols to be obsolete (they are not, but it cannot
be denied that SIP has dominated VoIP for several years now).
The SIP protocol is peer-to-peer and does not really have a formal trunk specification.
This means that whether you are connecting a single phone to your server or connecting
two servers together, the SIP connections will be similar.
The need to be able to connect two Asterisk
systems together to allow calls to be sent between them is a fairly common requirement.
Perhaps you have a company with two physical locations and want to have a PBX at
each location, or maybe you’re the administrator of the company PBX and you like
Asterisk so much that you would also like to install it at home. This section provides a
quick guide on configuring two Asterisk servers to be able to pass calls to each other
Connecting two Asterisk systems together with SIP.
#There are many proprietary PBX systems in the market that have a basic configuration that will work right
out of the box. Asterisk deployments are far more flexible, but seldom as simple.
VoIP | 147