3Com CoreBuilder 2500 User Manual - page 84
6-14
C
HAPTER
6: R
OUTING
WITH
IPX
Server Information Maintenance
When a router’s SAP agent receives a SAP broadcast response indicating a
change in a server’s configuration, the agent updates its server
information table and informs other SAP agents. Examples of such a
change are when a server is disconnected or becomes accessible through
a better route.
The SAP agent immediately sends an update broadcast to all directly
connected network segments except the segment from which the
information was received. All future periodic broadcasts contain the
change information.
SAP Aging
Router SAP agents use a special aging mechanism to deal
with a SAP agent that goes down suddenly without sending a DOWN
broadcast. A hardware failure, power interruption, or power surge can
cause this situation.
Each SAP agent maintains a timer for each entry in its server information
tables. This timer tracks the elapsed time since the entry has been
updated. This information is either new or changed, and the SAP agent
immediately passes it on, so changes are quickly captured and stored
throughout the intranetwork.
SAP Request Handling
When a SAP agent receives a general request,
it notifies the sending source about all servers known to the agent. This
response includes the same information that is sent out in periodic SAP
broadcasts. When the request is specific, the SAP agent notifies the
sending source about all servers of the requested type.