atom feed9 messages in net.launchpad.lists.openstack[Openstack] Quantum vs. Nova-network ...
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Dan WendlandtAug 24, 2012 3:38 pm 
Dan WendlandtAug 27, 2012 10:56 am 
Salvatore OrlandoSep 5, 2012 5:42 am 
Dan WendlandtSep 5, 2012 9:55 am 
Chris WrightSep 5, 2012 12:24 pm 
Syd (Sydney) LoganSep 5, 2012 1:59 pm 
rohon mathieuSep 7, 2012 8:36 am 
Dan WendlandtSep 7, 2012 9:56 am 
Syd (Sydney) LoganSep 7, 2012 10:34 am 
Subject:[Openstack] Quantum vs. Nova-network in Folsom
From:Dan Wendlandt (
Date:Aug 24, 2012 3:38:48 pm

tl;dr both Quantum and nova-network will be core and fully supported in Folsom.

Hi folks,

Thierry, Vish and I have been spending some talking about OpenStack networking in Folsom, and in particular the availability of nova-network now that Quantum is a core project. We wanted to share our current thinking with the community to avoid confusion.

With a project like OpenStack, there's a fundamental trade-off between the rate of introducing new capabilities and the desire for stability and backward compatibility. We agreed that OpenStack is a point in its growth cycle where the cost of disruptive changes is high. As a result, we've decided that even with Quantum being core in Folsom, we will also continue to support nova-network as it currently exists in Folsom. There is, of couse, overhead to this approach, but we think it is worth it.

With this in mind, a key question becomes: how do we "direct" users to the networking option that is right for them. We have the following guidelines:

1) For users who require only very basic networking (e.g., nova-network Flat, FlatDHCP) there's little difference between Quantum and nova-network is such basic use cases, so using nova's built-in networking for these basic use cases makes sense.

2) There are many use cases (e.g., tenant API for defined topologies and addresses) and advanced network technologies (e.g., tunneling rather than VLANs) that Quantum enables that are simply not possible with nova-network, so if these advanced capabilities are important to someone deploying OpenStack, they clearly need to use Quantum.

3) There are a few things that are possible in nova-network, but not in Quantum. Multi-host is the most significant one, but there are bound to be other gaps, some of which we will uncover only when people try their particular use case with Quantum. For these, users will have to use nova-network, with the gaps being covered in Quantum during Grizzly.

As a result, we plan to structure the docs so that you can do a basic functionality Nova setup with flat networking without requiring Quantum. For anything beyond that, we will have an "advanced networking" section, which describes the different advanced use of OpenStack networking with Quantum, and also highlight reasons that a user may still want to use nova-networking over Quantum.

Moving beyond Folsom, we expect to fully freeze the addition of new functionality to nova-network, and likely deprecate at least some portions of the existing nova-network functionality. Likely this will leave the basic flat and flat + dhcp nova networking intact, but reduce complexity in the nova codebase by removing more advanced networking scenarios that can also be achieved via Quantum. This means that even those using nova-network in Folsom should still be evaluating Quantum if they networking needs beyond flat networking, such that this feedback can be incorporated into the Grizzly deliverable of Quantum.