Version 7.2 753 Mediant 500L Gateway & E-SBC
User's Manual 39. Advanced SBC Features
♦ Source SIP Interface: Interface-2
♦ Source IP Group: IP-Phone-B
8. In the IP-to-IP Routing table, configure the routing rules:
• Index 0:
♦ Source IP Group: IP-Phone-A
♦ Destination IP Group: Primary-Proxy
• Index 1:
♦ Source IP Group: Primary-Proxy
♦ Destination IP Group:IP-Phone-A
• Index 2:
♦ Source IP Group: IP-Phone-B
♦ Destination IP Group: Sec-Proxy
• Index 3:
♦ Source IP Group: Sec-Proxy
♦ Destination IP Group: IP-Phone-B
39.6 Configuring Dual Registration
Some SIP entities (e.g., IP Phones) are setup to register with two registrar/proxy servers
(primary and secondary). The reason for this is to provide call redundancy for the SIP entity
in case one of the proxy servers fail. When the SIP entity registers with the proxy servers, it
sends two identical REGISTER messages - one to the primary proxy and one to the
secondary proxy. When the device is located between the SIP entity and the two proxy
servers, it needs to differentiate between these two REGISTER messages even though
they are identical. This is crucial to ensure that the device forwards the two registrations to
the proxy servers and that the device performs correct call routing between the SIP entity
and the two proxy servers.
To differentiate between these REGISTER messages, a unique SIP Interface needs to be
used for each REGISTER message. Each REGISTER message is registered in the
registration database using a unique "ac-int=<value>" string identifying the SIP Interface for
the Contact user. In addition, for SIP requests (e.g., INVITE) from the proxy servers, the
device needs to search its registration database for the contact user so that it can forward it
to the user. In normal registration, the host part of the Request-URI contains the IP address
of the device and therefore, there is no way of knowing which registered user the INVITE is
intended for. To overcome this issue, you can configure the device to use a special string
with a unique value, "ac-feu=<value>" for each registration, allowing the device to
differentiate between two registrations from the same user (identical REGISTER requests).
Each REGISTER message is registered in the registration database using the unique "ac-
feu=" string identifier for the Contact user.
A summary of how the device registers the two REGISTER messages in its registration
database is as follows:
1. The addresses of the proxy servers that are configured on the SIP entity (IP Phone)
must be the device's IP address with a different SIP local port for each one, for
example:
• Primary Proxy Server: 172.17.0.1:5060
• Secondary Proxy Server: 172.17.0.1:5080
2. When the device receives two identical REGISTER messages from the SIP entity, it
differentiates them by the SIP port on which they are received. The port allows the
device to associate them with a SIP Interface (5060 for "Interface-1" and 5080 for
"Interface-2").
3. The device performs SIP message manipulation (Pre-classification Manipulation) on
To Next Page
Loading...
