[openstack-dev] [neutron] Neutron scaling datapoints?

Neil Jerram Neil.Jerram at metaswitch.com
Thu Apr 9 15:01:45 UTC 2015

Hi Joe,

Many thanks for your reply!

On 09/04/15 03:34, joehuang wrote:
> Hi, Neil,
>  From theoretic, Neutron is like a "broadcast" domain, for example, enforcement of DVR and security group has to touch each regarding host where there is VM of this project resides. Even using SDN controller, the "touch" to regarding host is inevitable. If there are plenty of physical hosts, for example, 10k, inside one Neutron, it's very hard to overcome the "broadcast storm" issue under concurrent operation, that's the bottleneck for scalability of Neutron.

I think I understand that in general terms - but can you be more 
specific about the broadcast storm?  Is there one particular message 
exchange that involves broadcasting?  Is it only from the server to 
agents, or are there 'broadcasts' in other directions as well?

(I presume you are talking about control plane messages here, i.e. 
between Neutron components.  Is that right?  Obviously there can also be 
broadcast storm problems in the data plane - but I don't think that's 
what you are talking about here.)

> We need layered architecture in Neutron to solve the "broadcast domain" bottleneck of scalability. The test report from OpenStack cascading shows that through layered architecture "Neutron cascading", Neutron can supports up to million level ports and 100k level physical hosts. You can find the report here: http://www.slideshare.net/JoeHuang7/test-report-for-open-stack-cascading-solution-to-support-1-million-v-ms-in-100-data-centers

Many thanks, I will take a look at this.

> "Neutron cascading" also brings extra benefit: One cascading Neutron can have many cascaded Neutrons, and different cascaded Neutron can leverage different SDN controller, maybe one is ODL, the other one is OpenContrail.
> ----------------Cascading Neutron-------------------
>              /         \
> --cascaded Neutron--   --cascaded Neutron-----
>         |                  |
> ---------ODL------       ----OpenContrail--------
> And furthermore, if using Neutron cascading in multiple data centers, the DCI controller (Data center inter-connection controller) can also be used under cascading Neutron, to provide NaaS ( network as a service ) across data centers.
> ---------------------------Cascading Neutron--------------------------
>              /            |          \
> --cascaded Neutron--  -DCI controller-  --cascaded Neutron-----
>         |                 |            |
> ---------ODL------           |         ----OpenContrail--------
>                           |
> --(Data center 1)--   --(DCI networking)--  --(Data center 2)--
> Is it possible for us to discuss this in OpenStack Vancouver summit?

Most certainly, yes.  I will be there from mid Monday afternoon through 
to end Friday.  But it will be my first summit, so I have no idea yet as 
to how I might run into you - please can you suggest!

> Best Regards
> Chaoyi Huang ( Joe Huang )


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