3.4 Forwarder List
The source speci¯es the forwarder list in priority order
based on the expected cost of delivering a packet from each
node in the list to the destination. The cost metric is the
number of transmissions required to move a packet along
the best traditional route from the node to the destination,
counting both hops and retransmissions. This metric is similar
to ETX [4], differing in that ExOR uses only the forward
delivery probability. ExOR uses knowledge of the complete
set of inter-node loss rates to calculate these ETX values.
Figure 5 shows the ETX values to node E from each node
in the network of Figure 4. Each node's ETX value is the
sum of the link ETX values along the lowest-ETX path to