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Chapter 12
Value Added Services (VAS) Traffic Forwarding
VAS Traffic Forwarding and SCA BB
When VAS traffic forwarding is enabled, in addition to all its basic functions, the SCA BB application
classifies each flow as either a VAS flow or as a standard flow (non-VAS flow). This classification is
made on the first packet of the flow (for example TCP SYN packet). The classification must be
performed on the very first packet since the classification is used to select the routing of the packet to a
VAS server or to the subscriber/network.
VAS traffic forwarding rules are configured through the SCA-BB console. These rules map certain traffic
to the VAS Server Groups. When a flow is classified as a VAS flow, the VAS Server Group for this flow
is selected. If the group includes more than one VAS server, traffic will be forwarded in such a way that
the subscriber load is shared between the servers on the same group.
The mapping of traffic portions to VAS Server Groups is done through the standard SCA GUI, this
definition is given per package
VLAN Tags for VAS Traffic Forwarding
The traffic is routed between the SCE platform and the VAS servers by VLANs. There is a unique VLAN
tag for each SCE platform/VAS server combination.
Before being forwarded to the VAS servers, the SCE platform adds the VLAN tag to the original traffic.
When the traffic returns to the SCE platform, the SCE platform removes the VLAN tag it previously
added, and then forwards the traffic on its original link.
The VLAN tag to be used for each VAS server is configured by the user. To preserve consistency of the
traffic flow, the VAS solution requires the user to configure a unique VLAN tag for each SCE
platform/VAS server combination.
The VLAN tag format is shown in
Figure 12-2
11
The VLAN tag has twelve bits, divided as follows:
•
•
•
•
•
Observe the following for the nine bits that identify the SCE platform:
•
•
OL-7827-12
VLAN Tag Format
SCE unique prefix
10
9
8
The VLAN tag has twelve bits, divided as follows:
–
The lower three bits identify the VAS server.
The higher nine bits identify the SCE platform.
–
For example:
0x20 = 100 000 = SCE #4, VAS #0
0x21 = 100 001 = SCE #4, VAS #1
0x58 = 1011 000 = SCE #11, VAS #0
These nine bits must be the same for all VAS servers attached to a specific SCE platform.
These nine bits must be different for VAS servers attached to different SCE platforms.
Figure
12-2.
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6
5
4
Cisco SCE 2000 and SCE 1000 Software Configuration Guide
How VAS Traffic Forwarding Works
VAS #
3
2
1
0
12-5
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