[ovs-dev] [RFC] Proposal for enhanced select groups

[Ben Pfaff]

On Fri, Aug 22, 2014 at 09:19:41PM +0900, Simon Horman wrote:
> I have been working with Netronome on examining the possibilities of
> providing (richer) load balancing facilities in Open vSwitch.
> 
> It seems to us that the current select group provides for some load
> balancing functionality. And that in particular the way that it is
> implemented in Open vSwitch provides L2 destination load balancing (it
> hashes on the destination ethernet address). Our ideas so fare are as follows:
> 
> 1. Provide a richer and ideally extendible select group in the
>    form of an OpenFlow extension to groups.
> 
>    * Allow the fields used to be selected.
> 
>      In the case of a hash this would be the fields that are hashed.
> 
>      An implication of this is that the pre-requisites of these
>      fields would need to be present in the flow's match.
>      In masking of the fields would be allowed but not
>      required for fields whose TLVs allow masking.
> 
>    * Allow designation of the selection method used.
> 
>      For example hash.
> 
>    * Allow passing a parameter to the selection method.
> 
>      For example an initial value key for hashes.

There is an outstanding patch on this topic already:
        http://patchwork.openvswitch.org/patch/5424/

It sounds reasonable to make select groups configurable.  The way to do
that would be to implement the OpenFlow 1.5 (draft) proposal to add
properties to groups and group buckets, which is filed in the ONF JIRA
as EXT-350.

> 2. Investigate allowing selection of buckets to occur in the datapath. Or
>    in other words a megaflow with a select group action.  The current
>    select group implementation seems to be a good candidate for this
>    investigation.

Maybe this could be implemented via recirculation without datapath
changes, in the same way that bonds are implemented.