Administrator's Guide

2 Understanding the embedded applications
2.1 Link manager
The Link Manager builds information about links between network elements in the controller domain.
This application maintains a table of source and destination devices and ports, and transmits
discovery packets to ports on attached datapaths.
Link Manager
• Learns and maintains all inter-switch links in the control domain.
• Provides data used by the controller topology module to construct end-to-end paths.
• Deciphering port state changes.
• Generates link events to notify interested listeners.
• Identifies multi-hop links between disconnected segments of the control domain.
• Provides information used by applications to reconfigure flows when a link goes down.
NOTE: The controller injects BDDP packets for discovery. No LLDP packets are sent.
To avoid sending discovery packets on certain ports such as an edge port, LinkManager maintains
a special list of ports identified as "Suppressed LLDP Ports". Adding ports to the suppressed LLDP
list can be done using the REST API.
Link Service sends BDDP packets with LLDP payloads containing a TLV with an associated link
controller ID in one of the optional LLDP TLVs. This enables Link Service to differentiate the BDDP
messages it has generated.
As it is possible for non-OpenFlow devices to be present between OpenFlow switches, Link Service
also sends out BDDP messages to discover "multi-hop links", which refer to a link between two
OpenFlow switches on a path through one or more non-OpenFlow devices.
2.2 Node manager
• Learns and maintains end-host locations in the network.
• Uses information received from network devices to maintain the ARP table and end host data.
• Uses the Topology Service to determine if a port receiving a packet is an edge port or not.
• Learns and maintains end nodes in the controller domain, and associates end nodes with
edge ports.
• Builds an ARP cache with MAC-IP translations of end hosts.
• Maintains ARPs on a per-VID basis.
• Provides the edge port details for end hosts.
Example ARP table data:
VIDMACIP Address
10000:00:5e:00:53:01192.0.2.1
11000:00:5e:00:53:20192.0.2.2
12000:00:5e:00:53:02192.0.2.3
2.3 Path daemon
Path daemon is a "proof of concept" network service application built on top of the SDN controller.
10 Understanding the embedded applications