X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=DESIGN;h=c53a8ea3f54a839aaeb1b6a08d005961e5e8cefd;hb=4cf6a09c619d2c362ecfa688c90aadae4b1be39e;hp=2e3fced8067e681bf6f87877694d6c48ee3c3043;hpb=007948177581f3b3dad188221593d0e4bdca6ba0;p=sliver-openvswitch.git

diff --git a/DESIGN b/DESIGN
index 2e3fced80..c53a8ea3f 100644
--- a/DESIGN
+++ b/DESIGN
@@ -9,6 +9,38 @@ successful deployment.  The end of this document contains contact
 information that can be used to let us know how we can make Open vSwitch
 more generally useful.
 
+OpenFlow
+========
+
+The OpenFlow 1.0 specification requires the output port of the OFPAT_ENQUEUE
+action to "refer to a valid physical port (i.e. < OFPP_MAX) or OFPP_IN_PORT".
+Although OFPP_LOCAL is not less than OFPP_MAX, it is an 'internal' port which
+can have QoS applied to it in Linux.  Since we allow the OFPAT_ENQUEUE to apply
+to 'internal' ports whose port numbers are less than OFPP_MAX, we interpret
+OFPP_LOCAL as a physical port and support OFPAT_ENQUEUE on it as well.
+
+
+Multiple Table Support
+======================
+
+OpenFlow 1.0 has only rudimentary support for multiple flow tables.
+Notably, OpenFlow 1.0 does not allow the controller to specify the
+flow table to which a flow is to be added.  Open vSwitch adds an
+extension for this purpose, which is enabled on a per-OpenFlow
+connection basis using the NXT_FLOW_MOD_TABLE_ID message.  When the
+extension is enabled, the upper 8 bits of the 'command' member in an
+OFPT_FLOW_MOD or NXT_FLOW_MOD message designates the table to which a
+flow is to be added.
+
+The Open vSwitch software switch implementation offers 255 flow
+tables.  On packet ingress, only the first flow table (table 0) is
+searched, and the contents of the remaining tables are not considered
+in any way.  Tables other than table 0 only come into play when an
+NXAST_RESUBMIT_TABLE action specifies another table to search.
+
+Tables 128 and above are reserved for use by the switch itself.
+Controllers should use only tables 0 through 127.
+
 
 IPv6
 ====