How many Server Flows and/or Subscriber Flows are required for SIP Trunking?

A. one Subscriber Flow and two Server Flows

B. a minimum of two Subscriber Flows
C. one Subscriber Flow and one Server Flow
D. a minimum of two Server Flows

Two types of flows need to be defined for the proper routing of SIP messages from and to the endpoints and the SIP server.
• Server Flows – Routing destination sent by SIP server (Session Manager).
• Subscriber Flows – Routing destination sent by SIP endpoints.

Example, Server Flows:

References: Avaya Aura Session Border Controller Enterprise Implementation and Maintenance (2012), page 540, 546