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How VAS Traffic Forwarding Works
Examples of valid VLAN tag ranges for an SCE platform:
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•
The SCE platform enforces that the VLAN tags configured by the user keep this format, meaning that
the lower three bits match the VAS server number for which the VLAN tag is configured and that the
higher nine bits match the higher nine bits previously configured for other VAS servers on this SCE
platform. However, the SCE platform is not aware of the configuration of other SCE platforms, and
therefore it is the responsibility of the user to configure a unique nine bits (SCE id) for each SCE
platform.
Note that the use of VLAN tags is an integral part of the VAS solution, and therefore requires the VAS
device to be able to work in 802.1q trunk while preserving the VLAN information.
Service Flow
The mapping of traffic portions to VAS Server Groups is done through the standard SCA GUI, this
definition is given per package.
The SCE platform classifies a flow to a VAS Server Group based on the subscriber package and the
TCP/UDP ports of the flow. It then selects one server within this group to handle the flow.
The SCE platform performs load sharing between multiple VAS servers belonging to the same Server
Group; the balance is based on subscriber load. In other words, the SCE platform ensures that the
subscribers are evenly distributed between the VAS servers in the same group. Note that the mapping of
subscriber to a VAS server (per group) is kept even when servers are added or removed from the group
either due to configuration changes or changes in the operational status of the servers in the group. The
mapping will change only if the same server changes its status.
The following sections explain in more detail when and how the mapping is changed.
Data Flow
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•
In a deployment using VAS traffic forwarding, there are two types of data flows:
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•
The following figure depicts the two types of data flows running through a single SCE platform and a
single VAS server.
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•
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Cisco SCE 2000 and SCE 1000 Software Configuration Guide
12-6
0x20, 0x21 – 0x27, but not 0x33
0x58,0x59 – 0x5F, but not 0x26
Non-VAS Data Flow, page 12-7
VAS Data Flow, page 12-8
Non-VAS flow
VAS flow
Ports are illustrated as two uni-directional half ports, RX (on the left side) and the TX (on the right
side).
The SCE platform has four ports.
–
The VAS server has two ports.
–
For the sake of illustration, the SCE platform traffic flow direction is left to right while the VAS
traffic flow is right to left. The arrow below the name of the element indicates the traffic flow
direction.
The Ethernet switches are omitted.
Chapter 12
Value Added Services (VAS) Traffic Forwarding
OL-7827-12
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