SIP User's Manual 362 Document #: LTRT-83310
Mediant 600 & Mediant 1000
3. Number manipulation can be performed at both legs (inbound and outbound).
The following subsections discuss the main terms associated with the IP-to-IP call routing
application.
18.9.1.1 Proxy Sets
A Proxy Set is a group of up to five Proxy servers (for Proxy load balancing and
redundancy), defined by IP address or fully qualified domain name (FQDN). The Proxy Set
is assigned to IP Groups (of type SERVER only), representing the address of the IP Group
to where the device sends the INVITE message (destination of the call). Typically, for IP-
to-IP call routing, two Proxy Sets are defined for call destination – one for each leg (i.e.,
each IP Group) of the call (i.e., both directions).
18.9.1.2 IP Groups
An IP Group represents a logical SIP entity in the device's network environment such as an
ITSP SIP trunk, ITSP Proxy/Registrar server, IP-PBX, or remote IP-PBX users. The
address of the IP Group is typically defined by the Proxy Set that is assigned to it.
The opposite legs of the call are each presented by an IP Group: one being a Serving IP
Group; the other the Served IP Group. The Serving IP Group denotes the IP Group (e.g.,
ITSP) that provides service ("serves") to the Served IP Group (e.g., IP-PBX). This is the IP
Group to where the device sends INVITE messages received from the Served IP Group as
well as REGISTER messages for registering on behalf of the Served IP Group.
In addition, IP Groups can be SERVER or USER type. In SERVER IP Groups (e.g., ITSP
or IP-PBX), the destination address (defined by the Proxy Set) is known. In contrast, USER
IP Groups represents groups of users whose location is dynamically obtained by the device
when REGISTER requests and responses traverse (or are terminated) by the device.
Generally, these are remote IP-PBX users (e.g., IP phones and soft phones).
For registrations of USER IP Groups, the device updates its internal database with the
AOR and Contacts of the users (refer to the figure below) Digest authentication using SIP
401/407 responses (if needed) is performed by the Serving IP Group (e.g., IP-PBX). The
device forwards these responses directly to the remote SIP users. For a call to a registered
remote user, the device searches its dynamic database (by using the Request URI) for an
entry that matches a registered AOR or Contact. Once an entry is found, the IP destination
is obtained and a SIP request is then sent to this user.
Figure 18-45: IP-to-IP Routing/Registration/Authentication of Remote IP-PBX Users (Example)
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