SIP INVITE messages received at a load balancer are returned as SIP Redirect messages which are addressed to an access director and include additional information, such as a tracing token and a cryptographic token. When the access director receives the redirected SIP INVITE, the access director analyzes the included cryptographic token and passes the SIP INVITE if the cryptographic token is correct. This provides the needed access control function to allow the access directors to be directly accessed by the endpoints, rather than funneling all communications through the load balancer.