Whats a Business to Business call ?

When user place a call outbound from the enterprise to an external video service/customer or receive a call from external video service/customer over the internet its a business-to -business call.

How can we make it working?

Using Expressway servers we can make this working. Expressway C and E together form a firewall traversal solution and its the core component of B2B Communication.

How Expressway Firewall Traversal Works

1. Expressway-E is the traversal server installed in DMZ. Expressway-C is the traversal client installed within the
   enterprise network
2. Expressway-C connects via the firewall to a specific port on Expressway-E with secure login credentials.
3. Once the connection has been established, Expressway-C sends keep-alive packets to Expressway-E.
4. When Expressway-E receives an incoming call, it issues an incoming call request to Expressway-C.
5. Expressway C then initiates connection through CUCM to the endpoint
6. The call is established and media traverses the firewall securely

B2B Call Flow

Cisco SRV Records for business-to-business