With OVS 2.6, the Logical Switch table, in the hardware_vtep schema, has a new field, replication_mode. This bug will be used to add support to netvirt (touches ovsdb and genius, also) for setting the replication_mode of logical switches. The default will be for ODL to set the replication_mode to "source_node" when creating logical switches.

From vtep.5():

Replication Mode:

For handling L2 broadcast, multicast and unknown unicast traffic, pack‐
ets can be sent to all members of a logical switch referenced by a
physical switch. There are different modes to replicate the packets.
The default mode of replication is to send the traffic to a service
node, which can be a hypervisor, server or appliance, and let the ser‐
vice node handle replication to other transport nodes (hypervisors or
other VTEP physical switches). This mode is called service node repli‐
cation. An alternate mode of replication, called source node replica‐
tion involves the source node sending to all other transport nodes.
Hypervisors are always responsible for doing their own replication for
locally attached VMs in both modes. Service node replication mode is
the default and considered a basic requirement because it only requires
sending the packet to a single transport node.

replication_mode: optional string, either service_node or source_node
This optional column defines the replication mode per Logi‐
cal_Switch. There are 2 valid values, service_node and
source_node. If the column is not set, the replication mode
defaults to service_node.