Administrator's Guide

The Path Daemon application is responsible for pushing end-to-end flows for all ARP and IPv4 flow
misses that arrive at the controller. By default, Path Daemon is responsible for Layer-2 forwarding
only. This component depends on other network service components like Node manager and
Topology manager.
Path Daemon does the following:
• Registers with the controller as a Director. Directors are allowed to send a packet out.
• Registers for ARP packets and IPv4 packets.
• Uses the Node Manager to get the end hosts corresponding to the source and destination
MAC addresses and the switches to which these hosts are connected. It makes use of the
Topology Manager service to get the end-to-end path between the source and destination
switches. It makes use of the controller to push flows to the switches. The flowchart in Figure 1
provides more details of its operation.
• Path Daemon uses the following match fields when pushing a flow module. These match fields
have been chosen so that the flow modules are pushed on hardware tables in both Provision
and Comware switches.
◦ Ether Type
◦ Source Macaddress
◦ Destination Macaddress
◦ Input Port
◦ Output port
• Path Daemon also registers for Port Status Down messages. When such messages are received,
Path Daemon removes all flows configured for the impacted port, thereby causing the packet-ins
to again come to the controller.
Operation notes:
• Does not handle multicast and broadcast traffic
• Does not configure the reverse path along with the forward path
• Drops packets from sources that the controller has not learned
• Floods packets when their destinations are not known
• Does not support multi-pathing or fast-failover
• Performance is topology-dependent, recommended for 100-200 node environments
2.3 Path daemon 11