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

Mathieu Rohon mathieu.rohon at gmail.com
Tue Nov 25 16:14:47 UTC 2014

On Tue, Nov 25, 2014 at 9:59 AM, henry hly <henry4hly at gmail.com> wrote:
> 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.

Moreover, this solution is tested by the gate (at least ovs), and is
simpler for small deployments

> 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
> controller.

+100. Note that Dynamic routing is in progress.

> 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
> Henry
> 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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