[openstack-dev] [Neutron][L2 Agent][Debt] Bootstrapping an L2 agent debt repayment task force

henry hly henry4hly at gmail.com
Tue Nov 25 08:59:24 UTC 2014

Hi Armando,

Indeed agent-less solution like external controller is very
interesting, and in some certain cases it has advantage over agent
solution, e.g. software installation is prohibited on Compute Node.

However, Neutron Agent has its irreplaceable benefits: multiple
backends support like SRIOV, macvtap, vhost-user snabbswitch, hybrid
vswitch solution like NIC offloading or VDP based TOR offloading...All
these backend can not be easily controlled by an remote OF controller.

Also considering DVR (maybe with upcoming FW for W-E), and Security
Group, W-E traffic control capability gap still exists between linux
stack and OF flowtable, whether features like advanced netfilter, or
performance for webserver app which incur huge concurrent sessions
(because of basic OF upcall model, the more complex flow rule, the
less megaflow aggregation might take effect)

Thanks to L2pop and DVR, now many customer give the feedback that
Neutron has made great progressing, and already meet nearly all their
L2/L3 connectivity W-E control directing (The next big expectation is
N-S traffic directing like dynamic routing agent), without forcing
them to learn and integrate another huge platform like external SDN

No attention to argue on agent vs. agentless, built-in reference vs.
external controller, Openstack is an open community. But, I just want
to say that modularized agent re-factoring does make a lot of sense,
while forcing customer to piggyback an extra SDN controller on their
Cloud solution is not the only future direction of Neutron.

Best Regard

On Wed, Nov 19, 2014 at 5:45 AM, Armando M. <armamig at gmail.com> wrote:
> Hi Carl,
> Thanks for kicking this off. I am also willing to help as a core reviewer of
> blueprints and code
> submissions only.
> As for the ML2 agent, we all know that for historic reasons Neutron has
> grown to be not only a networking orchestration project but also a reference
> implementation that is resembling what some might call an SDN controller.
> I think that most of the Neutron folks realize that we need to move away
> from this model and rely on a strong open source SDN alternative; for these
> reasons, I don't think that pursuing an ML2 agent would be a path we should
> go down to anymore. It's time and energy that could be more effectively
> spent elsewhere, especially on the refactoring. Now if the refactoring
> effort ends up being labelled ML2 Agent, I would be okay with it, but my gut
> feeling tells me that any attempt at consolidating code to embrace more than
> one agent logic at once is gonna derail the major goal of paying down the so
> called agent debt.
> My 2c
> Armando
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