 part to destination SBC part to destination SBC Policy: IPv6 promotion Normal flow Destination SBC Dual-stack UA IPv4-only sends invite to IPv4-only Destination SBC Dual-stack Ua Policy: No IPv6 promotion called UA IPv6 promotion tagged sends invite to Policy: No IPv6 promotion solution (blue arrows) called UA are recommended Dual-stack UA Dual-stack UA Policy: IPv promotion Policy: IPve promotion Invite embeds Invite embeds IPv4 offer IPv4 offer Invite embeds Invite embeds Invite embeds Invite embeds ANAT offer IPv6 offer IPv6 offer ANAT offer by called UA by called UA 200 OK sent Destination SBC 200 OK sent Destination SBC Destination SBC 200 OK sent Destination SBC 200 OK sent sends 200 OK by called UA by called UA sends 200 OK sends 200 OK by called UA sends 200 OK by called UA IPv4-only core nodes Destination SBC Pv4-only core nodes Pv4-only core nodes Destination SBC Pv4-only core nodes can parse IPv6 sends 200 OK can parse IPv6 can parse IPv6 sends 200 OK can parse IPv6 information as per with IPv4 information as per information as per with IPv4 information as per RFC3261 information RFC3261 RFC3261 information RFC3261 IPv4-only core nodes IPv4-only core nodes IPv4-only core nodes IPv4-only core nodes can parse multiple can parse multiple can parse multiple can parse multiple contact information in cantact information in contact information in contact information in Destination SBC Destination SBC Destination SBC Destination SBC Destination SBC Destination SBC Destination SBC Destination SBC sends 200 OK sends 200 OK with sends 200 OK with sends 200 OK sends 200 OK sends 200 OK with sends 200 OK with sends 200 OK with IPv6 ANAT information- ANAT information- with IPv6 with IPv6 ANAT information- ANAT information- with IPv6 information IPv6 priority IPv4 priority information information IPv4 priority IPv6 priority information Policy: Originating SBC Originating SBC IPv6 promotion sends ACK with sends ACK with IPv4 information Policy: Policy: towards Policy: Policy: Policy: IPv4 information IPv6 promotion I