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VAS Redundancy
VAS Server Failure
The system monitors the health of a VAS server by periodically checking the connectivity between the
SCE platform and the VAS server. When the SCE platform fails to establish or maintain a connection to
the server within a configurable window of time, the state of the server is considered to be Down.
The implications of such state are:
•
•
•
If the connectivity to the server resumes, the state of the server is changed to Up. The server returns to
the list of active servers and will continue to serve subscribers that were mapped to it before the failure
and have not yet been mapped to a new server during the failure time, as well as new subscribers.
VAS Server Group Failure
For each VAS Server Group, the user can configure the following:
•
•
Note that if the minimum number equals the total number of configured servers, it means there is no
redundancy and failure of one server will cause the failure of the whole server group.
When the SCE platform detects that the number of active servers within a group is below the configured
minimum, it changes the state of the group to Failure. The configured action-on-failure will then be
applied to all new flows mapped for that VAS Server Group (existing flows will not be affected.)
There are two possible actions when the VAS Server Group has failed:
•
•
When the number of active servers is above the minimum and the state of the group is changed to Active
again, the configured action-on-failure is no longer applied to new flows. However, to maintain the
coherency of the network, flows that were Blocked or Passed are not affected by the change in the state
of the Server Group.
Ethernet Switch Failure
The Ethernet switches are a single point of failure in the VAS topology. A complete failure of an Ethernet
switch causes all the VAS services to be declared as failed and the configured action (on-failure) will be
taken for all new VAS flows.
Cisco SCE 2000 and SCE 1000 Software Configuration Guide
12-10
New logged-in subscribers will be distributed between the other active servers in the group.
Subscribers that are mapped to this server will be mapped to a new server if they initiate a new flow.
The Server Group may move to a Failure state if this failure caused the number of active servers in
the group go below the minimum configured.
The minimum number of active servers necessary.
The action to take in case the actual number of active servers goes below this number.
Block — all new flows assigned to the failed VAS Server Group will be blocked by the SCE
platform.
Pass — all new flows assigned to the failed VAS Server Group will be considered as regular
non-VAS flows, and will be processed without VAS service (that is, they will get SCA BB service
but not VAS service).
Chapter 12
Value Added Services (VAS) Traffic Forwarding
OL-7827-12
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