Vas Redundancy - Cisco SCE 8000 10GBE Software Configuration Manual

VAS Redundancy

VAS Redundancy
The VAS servers should be configured with high availability so that the failure of a single VAS server
will not degrade total system performance and availability. This requirement must be considered when
determining the number of VAS servers necessary for each VAS service.
There are two mechanisms that guarantee the performance and availability of the VAS services:
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In addition to failure of an individual VAS server, a complete VAS server group is considered to be failed
if a defined minimum number of servers are not active.
The following sections provide more information regarding the possible points of failure in a VAS traffic
forwarding deployment.
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VAS Server Failure
The system monitors the health of a VAS server by periodically checking the connectivity between the
Cisco SCE platform and the VAS server. When the Cisco SCE platform fails to establish or maintain a
connection to the server within a configurable window of time, the server is considered to be in Down
state.
When the server is in Down state:
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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 continues 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, you can configure:
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If the minimum number of active servers equals the total number of configured servers, it means there
is no redundancy and failure of one server causes the failure of the whole server group.
Cisco SCE 8000 10GBE Software Configuration Guide
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Load sharing—The Cisco SCE platform distributes the subscribers between all the active VAS
servers within a server group.
Monitoring—The Cisco SCE platform monitors connectivity with the VAS servers and handles
server failure according to the applied configuration.
VAS Server Failure, page 14-10
VAS Server Group Failure, page 14-10
Ethernet Switch Failure, page 14-11
Disabling a VAS Server, page 14-11
New logged-in subscribers are distributed between the other active servers in the group.
Subscribers that are mapped to this server are mapped to a new server if they initiate a new flow.
The server group may move to a Failure state if the failure caused the number of active servers in
the group to go below the minimum number configured.
The minimum number of active servers necessary.
The action to take in case the actual number of active servers goes below the configured minimum.
Chapter 14 Value-Added Services (VAS) Traffic Forwarding
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