Communication failures can occur in the following ways:
Transmit or receive path of the NIC can stop transmitting packets.
Attachment of the NIC to the link is down.
Port on the switch does not transmit or receive packets.
Physical interface in a group not present at system boot.
Host on the other end is not responding or the router that is forwarding the packets is not responding.
The Solaris implementation of IP network multipathing addresses the first four types of communication failures.