openstack team mailing list archive

[Dan Wendlandt <dan@xxxxxxxxxx>]

On Thu, Apr 26, 2012 at 12:55 PM, Salman Malik <salmanmk@xxxxxxxx> wrote:

>  Hi All,
>

Hi Salman,


>
> I am trying to learn the functionality of Quantum plugins used in
> OpenStack. I have read through the Quantum Admin Guide and had few
> basic/quick question about quantum and OVS interaction with it:
>
>
> 1) OVS can have ports in which vNICS can be plugged, so why does it need
> to use an integration bridge for connecting all VMs on the same node to a
> network?
>

I'm not sure I follow what question you're asking.  When OVS is running on
a host, it has one or more "bridges", and bridges have "ports".  A linux
device representing the vNIC must be added as a port of a bridge being
managed by the Quantum plugin.  We call this bridge the "integration
bridge".   The Quantum plugin can then configure the ports and bridges
appropriately to forward traffic based on the logical model created via the
Quantum API.  Can you be more precise about what you're asking here?



>
> 2) The OVS quantum plugin seems to implement the core API functions and
> (viewing the code) I concluded that it just makes maintains the logical
> mappings e.g. b/w net IDs and VLAN IDs in a database. So how is this
> mapping implemented on the actual ports of OVS? Is it the OVS quantum agent
> responsible for directing the packets to correct input/output ports based
> on the updates that it gets from the database?
>

In VLAN-mode, its even simpler than that.  The agent simply puts each port
as a VLAN access port for the right VLAN, based on the database, and then
has OVS perform standard L2 learning to forward packets.


>
> 3) The quantum admin guide says that the nova client will be the main user
> of quantum and will interact with it via REST API, so it would be nice if
> someone can point me to the code (file path name etc.) where this happens.
>

This is the QuantumManager code in Nova:
https://github.com/openstack/nova/tree/master/nova/network/quantum

One word of warning: this code will be being simplified and largely removed
in Folsom, so while its useful to look at it to learn about Quantum, I'd
ask around before investing the time to make significant changes to the
code.

>
>
> PS: What is the purpose of Quantum Manager in this architecture and where
> should I look for its code?
>

see above :)

Dan



>
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-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dan Wendlandt
Nicira, Inc: www.nicira.com
twitter: danwendlandt
~~~~~~~~~~~~~~~~~~~~~~~~~~~