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Re: Nova's network architecture


I will make a detailed description of this and where it is going.  I have a couple of branches cleaning up some of this, and some ideas for how it should be.  Briefly, the allocate and setup were split out so we could give a quick response from the api including the ip without having to wait for the setup, but it should really be returning 'pending' and doing all of the network setup at once with a call to nova-network from the compute host or the scheduler.  More after Nebula 1.0 (Monday)

On Oct 2, 2010, at 6:56 AM, Ewan Mellor wrote:

> Can someone please explain the intended architecture for Nova's networking
> code?
> Firstly, there is a daemon called nova-network, which I assumed would be
> responsible for managing networking in the entirety, but we also have
> nova-api handling networking configuration directly (calling
> network_manager.allocate_fixed_ip in response to a run_instance request)
> and nova-compute also doing some network setup (calling
> network_manager.setup_compute_network).
> I don't understand the dividing line of responsibility for these three
> (particularly why we need the API layer to allocate IP addresses, and how
> it's even possible to do this before the scheduler has had a chance to place
> the VM).
> Secondly, looking at the code in network.manager, I see a base class called
> NetworkManager, with two subclasses FlatManager and VlanManager, but
> NetworkManager also has a driver, of which we seem to only have one example:
> linux_net.
> I don't understand the division between these two orthogonal customization
> routes.  What belongs to the manager subclass, and what belongs to the driver?
> Thirdly, I don't understand the configuration of the network manager.  We've
> got a flag called "rs_network_manager" in the Rackspace API layer.  How is this
> different to flag called "network_manager" elsewhere?  What does it mean
> if these settings are different?  rs_network_manager=FlatManager,
> network_manager=VlanManager is the default at the moment, and I don't
> understand how that can have a sensible meaning.
> The reason I'm looking at all this at the moment is there are definitely
> going to be changes required to make this work with XenAPI, both for the
> existing bridging mechanism that we use, and for the upcoming Open vSwitch.
> I'm trying to figure out how these distinctions should be managed.
> Thanks in advance,
> Ewan.
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