ping message table...

from cisco's site...

http://www.cisco.com/en/US/docs/ios/12_3/configfun/command/reference/cfr_1g06.html#wp1075989

Character	Description
!	Each exclamation point indicates receipt of a reply.
.	Each period indicates that the network server timed out while waiting for a reply.
U	A destination unreachable error protocol data unit (PDU) was received.
C	A congestion experienced packet was received.
I	User interrupted test.
M	Could not fragment.
?	Unknown packet type.
&	Packet lifetime exceeded.