Frame Structure; Implementing Qinq - HP A5830 Configuration Manual

As shown in
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 PE device, 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 CE device.

Frame structure

A QinQ frame is transmitted double-tagged over the service provider network. As shown in
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.
Figure 49 Single-tagged Ethernet frame header and double-tagged Ethernet frame header
6 bytes
DA
Single-tagged frame structure
6 bytes
DA
Double-tagged frame structure
You must make sure that all ports on the path of a QinQ packet allow 1508-byte or larger frames to pass
through. The minimum size of a QinQ packet is 1508 bytes, which comprises two four-byte VLAN tags
and one 1500-byte standard Ethernet frame.

Implementing QinQ

HP provides the following QinQ implementations: basic QinQ and selective QinQ.
Basic QinQ
1.
Basic QinQ enables a port to tag any incoming frames with its port VLAN ID (PVID) tag, regardless of
whether they have been tagged or not. If an incoming frame has been tagged, it becomes a double-
tagged frame. If not, it becomes a frame tagged with the PVID tag.
Selective QinQ
2.
Selective QinQ is more flexible than basic QinQ. In addition to all functions of basic QinQ, selective
QinQ enables a port to perform the following per-CVLAN actions for incoming frames:
 Tag frames from different CVLANs with different SVLAN tags.
 Mark the outer VLAN 802.1p priority based on the existing inner VLAN 802.1p priority.
Figure 48, customer network A has CVLANs 1 through 10, and customer network B has
6 bytes 4 bytes
Customer
SA
VLAN Tag
6 bytes 4 bytes
Service
SA
VLAN Tag
Outer
VLAN tag
2 bytes 46-1500 bytes
Etype DATA
4 bytes 2 bytes 46-1500 bytes
Customer
Etype
VLAN Tag
Inner
VLAN tag
146
4 bytes
FCS
4 bytes
DATA FCS
Figure 49, the