An exemplary method includes at least on network element of a first network domain exchanging signaling and media border processing information with at least one network element of a second network domain by way of a secure packet-switched connection, exchanging service policy information with the at least one network element of the second network domain by way of the secure packet-switched connection, peering sessions associated with different service types between the first network domain and the second network domain by way of a packet-switched network-to-network interconnection interface (“NNII”) in accordance with the exchanged signaling and media border processing information, and enforcing different performance threshold specified by the service policy information for peering the sessions associated with the different service types.