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 100.100.100.100. This IP also has DNS record associated with fcsdk.com. FAS contains two applications: Application1 has two controlled domains fcsdk.com and example.com, Application2 has two controlled domains: url.net and cafex.com
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 Route:fcsdk.com matches Application 1
Application 1 processes the Request
Right Hand Side:
The Route:cafex.com matches Application 2
Application 2 processes the Request
Example 2:
The INVITE has a route (another.com), not destined for any Application
The Container will simply Proxy the Request onto another.com
Example 3:
The Route:100.100.100.100 does not match a controlled domain.
The Domain of the Request URI:example.com matches Application 1.
Application 1 will process the Request.
Example 4:
The Route:fcsdk.com does not match a controlled domain.
The Domain of the Request URI:example.com matches Application 1.
Application 1 will process the Request.
Example 5:
The Route:fcsdk.com 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:100.100.100.100 does not match a controlled domain.
The Domain of the Request URI:error.com 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 Route:cafex.com
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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