With the introduction of the full software-defined networking stack provided by OpenStack Networking (neutron) in the Folsom release, development effort on the initial networking code that remains part of the Compute component has gradually lessened. While many still use nova-network in production, there has been a long-term plan to remove the code in favour of the more flexible and full-featured OpenStack Networking.
An attempt was made to deprecate nova-network during the Havana release, which was aborted due to the lack of equivalent functionality (such as the FlatDHCP multi-host high availability mode mentioned in this guide), lack of a migration path between versions, insufficient testing, and simplicity when used for the more straightforward use cases nova-network traditionally supported. Though significant effort has been made to address these concerns, nova-network will not be deprecated in the Icehouse release. In addition, the Program Technical Lead of the Compute project has indicated that, to a limited degree, patches to nova-network will now again begin to be accepted.
This leaves you with an important point of decision when designing your cloud. OpenStack Networking is robust enough to use with a small number of limitations (IPv6 support, performance issues in some scenarios) and provides many more features than nova-network. However, if you do not have the more complex use cases that can benefit from fuller software-defined networking capabilities, or are uncomfortable with the new concepts introduced, nova-network may continue to be a viable option for the next 12 to 18 months.
Similarly, if you have an existing cloud and are looking to upgrade from nova-network to OpenStack Networking, you should have the option to delay the upgrade for this period of time. However, each release of OpenStack brings significant new innovation, and regardless of your use of networking methodology, it is likely best to begin planning for an upgrade within a reasonable timeframe of each release.
As mentioned, there's currently no way to cleanly migrate from nova-network to neutron. We recommend that you keep a migration in mind and what that process might involve for when a proper migration path is released. If you must upgrade, please be aware that both service and instance downtime is likely unavoidable.
