Openflow Node Discovery - HP HPE VAN SDN Controller 2.7 Administrator's Manual

the OpenFlow instance and port where they were received. Using the origin information
contained within the received packet, the controller derives the source and destination of
the link that this packet traversed and records a link between the OpenFlow instances.
The link type is derived from the destination MAC address of the packet (direct or multi-hop).
If a link is direct, it will be discovered as both direct and multi-hop from the reporting OpenFlow
instance, but the type direct has precedence over the type multi-hop, so the link is recorded
as direct.
hybrid.mode=false
All packets are stolen to the controller by default. Therefore, the OpenFlow Link Discovery
application does not push flow rules to devices.
A controller-generated link discovery packet:
Uses a non-standard protocol, BDDP, which uses a payload format similar to LLDP.
Is sent to either a link-local MAC address (to discover direct links) or a multicast MAC address
(to discover multihop links).
The link-local MAC address is: 01:08:c2:00:00:0e
The multicast MAC address used for link discovery is: 01:1B:78:E9:7B:CD.
Contains the source device and port that introduced the packet to the controlled network.
The OpenFlow Link Discovery application listens for PACKET_IN messages that contain the
BDDP protocol. Each discovery packet has the source device ID embedded within its payload,
and the destination device can be derived from the PACKET_IN message. This design enables
the OpenFlow Link Discovery application to populate the link table with information it learns from
such received packets.
NOTE: Because PACKET_IN messages that contain the BDDP protocol are for
controller-generated link discovery packets, no corresponding PACKET_OUT is sent back to the
device that sent the PACKET_IN.
The OpenFlow Link Discovery application also listens to device and interface events and registers
with the ControllerService API to send OpenFlow packets to datapaths.
If the OpenFlowLinkDiscoveryComponent configuration has age.multihop.links=true,
the OpenFlow Link Discovery application periodically injects discovery packets into the controlled
network to refresh the multihop links. Any multihop links that are not refreshed at the interval
configured for the multihop.poll.interval key are considered to be invalid and are removed
from the link table. Additionally, network events such as a port going down or a device status
change causes relevant links to be removed from the link table, and causes discovery packets
to be sent to all datapaths that are in a ready state.

OpenFlow Node Discovery

The OpenFlow Node Discovery application is the default OpenFlow node supplier application
that is installed with the controller. This application implements the
com.hp.sdn.supplier.NodeSuppliersBroker interface and uses NodeSupplierService
and NodeService APIs to create and maintain node information for OpenFlow datapaths that
register with the controller.
If the ControllerManager configuration has hybrid.mode=false, all packets are implicitly stolen
to the controller and processed by the OpenFlow Node Discovery application. If learn.ip=true,
the node discovery application in this case uses ARP, DHP and IP packets to discover the hosts.
16 Understanding the controller architecture