[ovs-discuss] openvswitc forwarding modes

ravi kerur rkerur at gmail.com
Thu Jul 12 18:23:21 UTC 2012


On Thu, Jul 12, 2012 at 2:26 AM, <mvpbl_c at iol.pt> wrote:

> **
>
> Hello,
>
> I have two questions about OpenvSwitch and I hope someone can advise me.
> In the openvswitch features they speak about:
> -Kernel and user-space forwarding engine options
> -Multi-table forwarding pipeline with flow-caching engine
> What this means? can you give me some advise?
>
> In the normal switch it exist three forwarding modes, from what I know.
> Is possible in openvswitch to also specify one of three possible
> forwarding modes for each port, like:
> 1-Cut-through
> 2-Fragment-free
> 3-Store-and-forward
>
>
Software switching can be close to Store-and-forward mechanism since
packets are in skb's, headers extracted, matched and forwarded or dropped
or something other actions based on the configured actions.Cut-through
mechanism doesn't generally apply to NIC based switching.

w.r.t openvswitch forwarding options, kernel-space switching happens in
kernel if there is a matching entry else punted to userspace, userpspace
installs a flow and subsequent packets are switched in kernel, user-space
switching everything hapens in user land via tun/tap interface. I have just
given general explanation of what they are, you need to look into kernel
and user-space code to understand better.

> If this is possible, can someone give me a tip of how can I do this.
>
> Sorry for bother,
>
> Thanks in advanced,
> Best Regards,
> Cruz Marco
>
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>
>
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