7). It is used between two DIAMETER servers to exchange
information about the capabilities of the server. Either end of a DIAMETER dialog would
send this to the other node to request information about the capabilities of the server.
The Capabilities-exchange-answer (CEA) message is sent in response to the CER,
by either the network element or the OCS (depending on who originated the CER; see
Table 7.8). The answer provided in this message communicates the capabilities of the
server or entity answering. For example, a charging platform would use this message
to communicate to a network element that it supports the DIAMETER protocol and
supports online charging.
Device-watchdog-request (DWR) is sent by either the network element or the OCS,
when there has been a lapse in traffic between the two nodes (see Table 7.9). The request
is sent to determine if there was a failure in the facilities. The sending node is
expecting to receive an answer in response; if no response (DWA) is received, then the
node assumes that the communications path between the two entities has failed.
Device-watchdog-answer (DWA) is sent in response to a DWR, by either the network element
or the OCS (dependent on who originated the DWR; see Table 7.10). The DWA assures
the opposite node that transmission between the two entities is still operational.
DIAMETER Attribute-Value Pairs (AVPs) The AVPs are the parameters used within the
DIAMETER messages to provide information regarding an event or the originator of an
event.
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