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Hi Hitesh,
Thanks for the considerate reply.
Please see the inline comments.

On Fri, Apr 27, 2012 at 1:25 AM, Salman Malik <salmanmk at live.com> wrote:



Hi All,

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?

[Hitesh]:
As far as I know that OVS have more features over the Linux bridge, for example, VM isolation, mobility and security. These can be configured by remote controller. To help and gian the control on all these activities the integration bridge is required. I am not sure about it but I Dan or Salvotore can explain this better way. You can find the more information here http://openvswitch.org/support/

Now, what I have understood from Dan's reply is that OVS itself consists of these bridges (each bridge on a node, being called as an "integration bridge"). Correct me if I am wrong.


  
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?

[Hitesh]:
OVS agent is responsible for to update the database(accoding to actions have been told) for the local server as well Quantum server. As far as I know OVS quantum is not responsible for directing the packets to correct in/op,  This job is hadled by OVS core module on the server (datapath). OVS agent only updates the database and creation bridge etc.. Dan or Salvotore can be explained more...


Are you sure that quantum agent updates the database? I used to think that it only grabs updates by looking into the database (which is actually modified by the plugin). I am not sure so just confirming.

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.


[Hitesh]:
You can see the devstack script where we are configuring nove-network to quantum. thats the enry point for the nova-network to communicate to quantum. I will share soon more on this.

Thanks Hitesh for sharing you knowledge :) Can you comment on how nova-network interacts with Quantum-manager?

 
However, I tried my best to give to these answers. Please feel free to correct me if anything needs to share more.
 
Salman, Let me know if you want more info about this. I will be happy to share


Thanks again Hitesh. I appreciate your help.
Salman

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