What are the necessary
to SIP-enable a gateway, in a situation where I directly connect the analog phone to the gateway?
What is SIP-T?
There is no RFC support required to connect an analog phone to an
port on a gateway. The RFC support comes into play only on the Ethernet side of the gateway where the gateway has to connect to an external SIP server. In that case, RFC 3261 is the base RFC. From there, it will just depend on what feature set can be supported by the gateway and the associated SIP server. Typically the ITSP providing the SIP service will have a recommended list of gateways it supports.
SIP-T is defined in RFC 3372. It does not really apply to the scenario above. It explains how to bridge between SS7 networks on the PSTN with an IP network in the middle using SIP to encapsulate the SS7 messaging.