A PAC and PNS must have only one control connection between them. It is possible, however, for a PNS and a PAC to simultaneously attempt to establish a control connection to each other. When a Start-Control-Connection-Request is received on one TCP connection and another Start-Control-Connection-Request has already been sent on another TCP connection to the same peer, a collision has occurred.
The "winner" of the initiation race is the peer with the higher IP address (compared as 32 bit unsigned values, network number more significant). For example, if the peers 192.33.45.17 and 192.33.45.89 collide, the latter will be declared the winner.
The loser will immediately close the TCP connection it initiated, without sending any further PPTP control messages on it and will respond to the winner's request with a Start-Control-Connection-Reply message. The winner will wait for the Start-Control-Connection-Reply on the connection it initiated and also wait for a TCP termination indication on the connection the loser opened. The winner MUST NOT send any messages on the connection the loser initiated.