User guide

VOIP INFORMATION 129
What is a SIP Proxy and Registrar?
SIP’s basic architecture is client/server in nature. The main entities in the
SIP server are the Proxy, Redirect Server and the Registrar.
TalkSwitch 48-CVA has the SIP Server fully integrated for easy deployment
and maintenance of your VoIP network. If you are deploying a multi-site
configuration which can comprise of TalkSwitch 48-CVA units, certified 3rd
party gateways and certified 3rd party SIP phones, one TalkSwitch
48-CVA can act as the SIP Proxy and Registrar. The other SIP end-points will
register with this TalkSwitch 48-CVA and all calls will be negotiated through
this TalkSwitch 48-CVA.
When you first set up your VoIP device (TalkSwitch 48-CVA, gateway or
phone), it will register itself with the TalkSwitch 48-CVA that is configured
as the SIP Server so that calls can be directed to your location.
When you initiate a VoIP call, your device (TalkSwitch 48-CVA, gateway or
phone) will contact the TalkSwitch 48-CVA that is configured as the SIP
Server to obtain the contact information for the destination you are trying
to reach. Once the information is received, the call is established directly
between your location and the destination. The SIP Server is no longer
involved in the call.
If the location of the SIP Proxy and Registrar has a Dynamic IP Address, you
have to use Dynamic DNS since the SIP Server location becomes unreachable
as soon as the IP address changes.
What is Dynamic DNS?
Dynamic DNS is a Domain Name Service used with Dynamic IP addresses. DNS
is used to allow devices to find other devices on the Internet by name rather
than by IP address. Dynamic DNS allows you to use a domain name — FQDN
(which does not change) to locate a device with a Dynamic IP address. There
are companies on the Internet which can provide you with a DNS address,
even if your IP address changes. For example, www.dyndns.org or hn.org or
www.no-ip.com. You should consult with them about how to use their
service. The basic idea is that you will receive an address like
myname.homeip.net which points to your IP address (i.e. 209.210.230.140).
This is important for locations where the SIP Server resides and where the
public IP address is dynamic. All other locations will point to this SIP
Server’s domain instead of an IP address.