PAA server

Figure: The PAA-server operations.
\includegraphics[width=5in]{gfx/paa-server.eps}

The basic operations of the PAA-server is illustrated in figure 12.10.

The first thing PAA does when going from client- to server-mode is to connect to the routing-daemon via a TCP socket to the loopback device (127.0.0.1 or ::1).

Upon receiving an Address Request from a PAA-client the PAA-server queries the routing protocol for a free address. In the implementation, this means querying the PAA-plugin via IPC. If the Address Request contains a preferred address, this is passed to the OLSR daemon in the query message. When using IPv6 the MAC address of the sender is always passed in the message. If no free IP addresses can be allocated, the PAA-server will transmit an Address Response message with the FAILIURE flag set. If an IP offer is received from the routing protocol, an Address Response message is generated containing the offered IP, the ID and SEQNO from the received Address Request.

Upon receiving an Address Test message link-local, the PAA-server forwards this message to the routing protocol if the FORWARDED flag is not set in the message. This is to prevent forwarding of messages forwarded link-local from other PAA-servers, which can lead to loops. The PAA-server then sends an Address Test Response message back to the PAA-client to confirm that the message has been received and is currently being processed.

A PAA-server should only forward messages link-local if there exists any unconfigured 1 hop neighbors. To detect this, the PAA-server listens for Forward Request messages which are sent periodically by unconfigured nodes. Upon receiving a Forward Request the forward timer of the server is set to current time + a predefined holding time. Upon receiving an Address Test message from the routing protocol, the PAA-server broadcasts or multicasts this message link-local, setting the FORWARDED flag, if the forward timer is not expired.

Andreas 2004-07-29