EVPL (QinQ) services realize VLAN nesting. The current number of VLAN IDs cannot meet the requirement with the increase of network users. With the configuration of the EVPL (QinQ) service, users can be identified through multiple layers of VLAN IDs. In this case, the VLAN is extended.
The VLAN is a LAN technology developed along with the Ethernet switch technology. As the Ethernet technology is deployed largely in the networks of carriers, which are the metropolitan area networks, separating and identifying users by using the 802.1Q VLAN are limited. The VLAN tag domain that is defined in the IEEE 802.1Q has 12 bits, which can represent 4K VLANs only. This cannot meet the requirements for identifying a large number of users in metropolitan area networks. In order to increase the number of VLANs, the QinQ technology is developed.
The QinQ technology is realized by adding a layer of 802.1Q tags to 802.1Q packets. Thus, the number of VLANs is increased to 4K x 4K. Along with the development of the metropolitan area network and the requirements of carriers on the fine operation, application scenarios for the double tags of the QinQ are increased. The inner and outer tags can represent different information. The inner tag (namely the C-VLAN) represents the client and the outer tag (namely the S-VLAN) represents the service. See Table 1.
Operation |
Description |
Illustration |
|---|---|---|
Add S-VLAN Tag |
Adds S-VLAN based on the PORT. |
|
Add S-VLAN and C-VLAN Tag |
Adds S-VLAN and C-VLAN based on the PORT. |
|
Transparently transmit C-VLAN Tag |
Transparently transmit C-VLAN |
|
Transparently transmit S-VLAN Tag |
Transparently transmit S-VLAN |
|
Translate S-VLAN Tag |
Translate S-VLAN based on the PORT. |
|
