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Understanding FAS Controlled Domains

Fusion Application Server (FAS) can host multiple SIP/HTTP applications.  In order for SIP messages to be routed to the correct application FAS allows each application to have a number of Controlled Domains. The SIP container will inspect an initial SIP Request to determine if there is a suitable Domain.

This article focuses on SIP Requests arriving at FAS from an External Entity (eg: another SIP client); it does not cover Requests generated by an application, nor routing between applications hosted on the same FAS.

Also note, that all the examples here are for Initial INVITE Requests; subsequent requests already have a determined application path and will not be Routed.

All the examples consider FAS is installed on a host with an IP address  This IP also has DNS record associated with  FAS contains two applications: Application1 has two controlled domains and, Application2 has two controlled domains: and

Each of the diagrams below show, one or two inbound Initial INVITE requests destined for FAS.  On receipt of a SIP Request, FAS will inspect the top-most route header or request uri to determine the next Domain to route to.


Example 1:

Left Hand Side:

The matches Application 1

Application 1 processes the Request

Right Hand Side:

The matches Application 2

Application 2 processes the Request

Example 2:

The INVITE has a route (, not destined for any Application

The Container will simply Proxy the Request onto


Example 3:

The Route: does not match a controlled domain.

The Domain of the Request matches Application 1.

Application 1 will process the Request.

Example 4:

The does not match a controlled domain.

The Domain of the Request matches Application 1.

Application 1 will process the Request.


Example 5:

The matches no Controlled Domain

The Container will route the Request back to itself; having performed a DNS query. Eventually, the Max-Forward's header is exceeded, the container will create a 483 - Too Many Hops Response


Example 6:

The Route: does not match a controlled domain.

The Domain of the Request does not match a controlled domain AND it not is it resolvable.

The container cannot route the request, so generates a 500 Server Internal Error Response

Example 7:

Left Hand Side:

In this example the Route does not match any Application Domain

However, a Default Application Router is set

In this case, Application 1 will process the Request

Right Hand Side:

The Request has a

Even though there is a Default Application Router, the Route matches the Controlled Domain for Application 2.

Application 2 will process the request








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