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Cisco SCE 8000 10GBE Software Configuration Guide
OL-30621-02
Chapter 14 Value-Added Services (VAS) Traffic Forwarding
How VAS Traffic Forwarding Works
The following sections provide a more detailed description of how VAS traffic forwarding works.
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Requirements for VAS Servers, page 14-4
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VAS Traffic Forwarding and SCA BB, page 14-5
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VLAN Tags for VAS Traffic Forwarding, page 14-5
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Requirements for VAS Servers
Because the VAS devices are installed behind the Cisco SCE platform, they should follow the network
behavior of the Cisco SCE platform. Therefore, VAS devices must meet the following two requirements:
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VAS devices must be equipped with separate interfaces for the subscriber side and separate
interfaces for the network side.
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Traffic towards the subscribers should be sent from the subscriber interface and from the network
interface for the internet.
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VAS devices must be transparent in Layer 2. The VAS servers must act like Layer 2 switches, in that,
they are not allowed to change traffic headers or to generate new traffic..
Layer 2 Transparency
To handle non-management traffic of VAS services, follow these guidelines:
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The VAS services should work in promiscuous-mode in Layer 2 and accept packets with any
destination MAC address.
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When forwarding traffic back to the network after processing, the VAS devices must preserve the
original Layer 2 headers containing the MAC addresses and the VLAN tag. The VAS devices must
not change the MAC addresses (destination or source) or the VLAN tags. The following restrictions
apply to the injected traffic:
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The VAS device is not permitted to initiate new flows.
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New traffic can be injected only in the context of an existing flow.
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When injecting traffic, the Layer 2 information (MAC addresses, VLAN tags, and the TCP/IP
parameters) must be taken from the flow into which the traffic is being injected.
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A VAS device must not generate its own network transactions or relay such transactions. Network
transactions such as ARP requests or pings are not permitted.
VAS Management Traffic
VAS devices that are managed inband (through the traffic interface) must meet the following
requirements:
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Management traffic should either be carried over a dedicated VLAN or without any VLAN header.
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The switches that are connected to the VAS devices should be directly connected to the POP router.
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The switches that are connected to the VAS devices should be configured so that management traffic
is sent directly to the router and not through the Cisco SCE platform.
