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Chapter 12
Value Added Services (VAS) Traffic Forwarding
In the VAS over 10G topology, a failure may occur at any of the following three points:
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•
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Health Check in VAS over 10G Topology
In the VAS over 10G topology, special attention must be paid to the selected IP addresses of the health
check flows. A flow initiated by an SCE platform may not always be hashed correctly by the
EtherChannel. Therefore, a health check packet can be sent out from one SCE platform, go through the
7600/6500 towards the VAS server, then be sent back from the VAS server through the 7600/6500 but
hashed by the EtherChannel to a SCE platform different than the originator SCE platform.
To prevent this from happening, the SCE platform opens eight flows per VAS server. This ensures that
at least one of the flows will be mapped to the correct SCE platform; the other SCE platforms disregard
health check packets not initiated by them.
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Failure of an SCE platform
SCE platform failure is detected and handled by the 7600/6500 device. In such case, the
EtherChannel will balance the traffic load between the other active SCE platforms. SCA BB and
VAS service through the other SCE platforms continues uninterrupted with no change in the VAS
link.
Failure of a 7600/6500
The 10G link that goes through the failed 7600/6500 device is lost completely, however SCA BB
and VAS services on the 10G link that goes through the second 7600/6500 device continue
uninterrupted. In case of failure of the 7600/6500 that is connected to the active set of VAS servers,
all the VAS traffic of the other 10G link is forwarded to the standby set of VAS servers
Failure of a VAS server group
Failure of a VAS server group on the active VAS traffic link is detected by the VAS health check.
Failure of any VAS server group triggers the switch of the entire link to the standby VAS servers. A
server group failure is declared when the number of active VAS servers drops below the parameter
"minimum active VAS servers in a group" (see
Parameters, page
12-26).
Both links preserve SCA BB and VAS services. However, during the transition period, the replacing
VAS servers will see VAS flows in the middle and the VAS service may be temporarily damaged.
How to Configure VAS Server Group Failure
Cisco SCE 2000 and SCE 1000 Software Configuration Guide
VAS over 10G
12-39
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