Routing to accomodate SIP applications.
The Deep Packet Inspection capable firewalls offer the ability to apply Routing and Dial Plan rules to all incoming SIP traffic. As the Ingate product has the ability to look at Layer 2 through Layer 7 of the OSI model, Routing and Dial Plan rules can combine the use of several layers at once. Combining such things as the TCP/IP (Transport Layer) with the SIP protocol (Application Layer) ensures that only predefined SIP traffic is processed.
Best Routing Rules:
The actual Dial Plan, then, combines these three attributes to provide the ultimate in flexibility and security in defining:
This also gives the ability to have multiple different IP-PBX vendors and multiple different ITSP accounts. N+1 ITSPs to N+1 IP-PBXs. There is no limit to the customization of call routing in some routers.
Policies related to SIP have to do with allowing or disallowing SIP traffic based on SIP Methods, SIP Mime Content, SIP Domains and other higher-level rules. A SIP Method policy can be implemented to ensure incoming SIP packets are matched on the particular SIP Method and Traffic to specified domains. If required, Authentication can be applied for processing the packet. Further policies can be applied to filter MIME Content types, to ensure the type of SIP Traffic is allowed. Filtering based on specific Header information is also possible.
Other Routing Rules and Policies can also be applied to allow for SIP Domain forwarding, Static SIP URI forwarding, SIP Registrar Authentication, and more.