An IKE security association (SA) is a set of parameters that define how the Internet Key Exchange (IKE) protocol will authenticate and establish the secure channel between the IPsec VPN peers. When you configure an IPsec VPN, one IKE SA is created between the peers, regardless of how many CoS forwarding classes are used to separate the traffic. The SA will be used to negotiate the IPsec SA parameters, such as encryption algorithms and keys.
In this scenario, only 1 IKE security association is required between the IPsec peers, no matter how many CoS forwarding classes are used to separate the voice and data traffic.