SIP registry and DNS SRV
All SIP phones require that we configure some parameters, at least the SIP server address or name. This server address is used when the phone needs to enter the voice over IP network and registers itself to the registrar1. The registrar keeps a database of the associated phone with their IP address and the UDP or TCP port they can be joined on, by default the 5060. On top of that mechanism, each call requires some exchanges with a SIP proxy, this one can route the call to its destination or some other proxy server. The proxy location can either be entered in the phone configuration or using a dynamic service that can resolve name versus IP address. Let see how these processes are working and how to implement these.
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- not the SIP proxy as sometimes stated [↩]
