3. Constraints and challenges

3.1 Global IPv6 connectivity: avoiding IPv6 Internet fragmentation

The density of interconnection agreements between IP connectivity operators, the meshing of the IPv4 Internet, the reliability of IPv4 engineering rules (e.g. inter- and intra-domain routing policies) and operators' expertise in diagnosing and resolving faults have made the IPv4 Internet more robust and reliable. Maintaining Internet robustness (i.e. guaranteeing at least the same level of robustness as IPv4-only Internet) is a challenge for current and future IPv6...