[ovs-dev] OFPMT_TABLE_FEATURES is supported in OVS or not

Jean Tourrilhes jt at hpl.hp.com
Wed Mar 11 17:58:24 UTC 2015


tech_kals Kals wrote :
> 
> Switch can maintain any number of flow tables. But, the controller will
> come to know about it only through "OFPMT_TABLE_FEATURES".

	That's incorrect.
	Currently, the main method for hardware switches is to use an
out-of-band mechanism. If you look at any hardware switch, there is
usually explicit documentation about what tables are implemented and
what each table supports. The controller just has a driver for each
switch type.
	This method is currently being formalised using the TTP
language, so that all vendors express their table structures the same
way. Currently TTPs are only out-of-band, so you need to input then in
your controller somehow, TTP v1.1 may add the ability to negociate
TTPs in-band and for the controller to query it from the switch.

	For software switches, such as OVS and CPqD SoftSwitch, it's
even more trivial. Software switches do support all possible
table-ids, and all features are supported in all tables. In other
words, the controller can just blindly program all the tables any way
it wants, use any table-id it want and any feature it want, it will
always work.

	Ben already told you that OFPMT_TABLE_FEATURES (read-only) is
supported in OVS 2.4. This is a new feature, so it would obviously
benefit from more testing and people pushing it to the limit. As you
seem to have very clear idea on how you want to use that feature, you
should upgrade to OVS 2.4 (OVS trunk) and test it exhaustively for
your use case and report bugs. I think it would be a more productive
use of everybody's time.

	Regards,

	Jean



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