During IKE negotiation, there can be multiple traffic selectors
for different networks and protocols. For example, the Initiator
might indicate that it wants to send TCP packets from 172.168.0.0/16
through the tunnel to its peer, destined for 198.5.0.0/16. It also
wants to send UDP packets from 172.17.0.0/16 through the same tunnel
to the same gateway, destined for 0.0.0.0 (any network). The peer gateway
must agree to these traffic selectors so that it knows what to expect.