The source code for this package is located in src/gov/nist/sip/proxy. The proxy is a pure JAIN-SIP application: it does not need proprietary nist-sip classes in addition of those defined in JAIN-SIP 1.1, you can substitute the NIST-SIP stack by another JAIN-SIP-1.1 compliant stack and it should interoperate. he proxy can act as presence server and be able to process NOTIFY and SUBSCRIBE requests. If this parameter is disabled, the proxy will simply forward those kind of requests following the appropriate routing decision.