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 favor 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.
