HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 2 - LAN Switching Co - Page 164

QinQ frame structure, Typical QinQ application scenario

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Figure 49 Typical QinQ application scenario As shown in Figure 49, customer network A has CVLANs 1 through 10, and customer network B has CVLANs 1 through 20. The service provider assigns SVLAN 3 for customer network A, and assigns SVLAN 4 for customer network B. When a tagged Ethernet frame from customer network A arrives at a provider edge device (PE), the PE tags the frame with outer VLAN 3. When a tagged Ethernet frame from customer network B arrives at a PE, the PE tags the frame with outer VLAN 4. There is no overlap of VLAN IDs among customers, and traffic from different customers can be identified separately. The double-tagged Ethernet frame is then transmitted over the service provider network and arrives at the other PE. The PE removes the SVLAN of the frame before sending it to the target customer edge device (CE). QinQ frame structure A QinQ frame is transmitted double-tagged over the service provider network. As shown in Figure 50, the inner VLAN tag is the CVLAN tag, and the outer one is the SVLAN tag that the service provider has allocated to the customer. QinQ uses CVLAN tags to transmit frames over the private network, and uses SVLAN tags to transmit frames over the public network. When a QinQ frame is transmitted over the public network, its CVLAN tag is transmitted as the payload. 155

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155
Figure 49
Typical QinQ application scenario
As shown in
Figure 49
, customer network A has CVLANs 1 through 10, and customer network B has
CVLANs 1 through 20. The service provider assigns SVLAN 3 for customer network A, and assigns
SVLAN 4 for customer network B.
When a tagged Ethernet frame from customer network A arrives at a provider edge device (PE), the PE
tags the frame with outer VLAN 3. When a tagged Ethernet frame from customer network B arrives at a
PE, the PE tags the frame with outer VLAN 4. There is no overlap of VLAN IDs among customers, and
traffic from different customers can be identified separately.
The double-tagged Ethernet frame is then transmitted over the service provider network and arrives at the
other PE. The PE removes the SVLAN of the frame before sending it to the target customer edge device
(CE).
QinQ frame structure
A QinQ frame is transmitted double-tagged over the service provider network. As shown in
Figure 50
,
the inner VLAN tag is the CVLAN tag, and the outer one is the SVLAN tag that the service provider has
allocated to the customer.
QinQ uses CVLAN tags to transmit frames over the private network, and uses SVLAN tags to transmit
frames over the public network. When a QinQ frame is transmitted over the public network, its CVLAN
tag is transmitted as the payload.