ZyXEL Communications IES-708-22A - Manual (Page 205)

IES-708-22A User’s Guide
205
C
H A P T E R
31
TLS PVC
This feature is available in STU-C mode only.
This chapter shows you how to set up Transparent LAN Service (VLAN stacking, Q-in-Q) on
each port.
31.1 Transparent LAN Service (TLS) Overview
Transparent LAN Service (also known as VLAN stacking or Q-in-Q) allows a service provider
to distinguish multiple customers VLANs, even those with the same (customer-assigned)
VLAN ID, within its network.
Use TLS to add an outer VLAN tag to the inner IEEE 802.1Q tagged frames that enter the
network. By tagging the tagged frames (“double-tagged” frames), the service provider can
manage up to 4,094 VLAN groups with each group containing up to 4,094 customer VLANs.
This allows a service provider to provide different services, based on specific VLANs, for
many different customers.
A service provider’s customers may require a range of VLANs to handle multiple
applications. A service provider’s customers can assign their own inner VLAN tags to traffic.
The service provider can assign an outer VLAN tag for each customer. Therefore, there is no
VLAN tag overlap among customers, so traffic from different customers is kept separate.
Before the IES-708-22A sends the frames from the customers, the VLAN ID is added to the
frames. When packets intended for specific customers are received on the IES-708-22A, the
outer VLAN tag is removed before the traffic is sent.
31.1.1 TLS Network Example
In the following example figure, both A and B are Service Provider’s Network (SPN)
customers with VPN tunnels between their head offices and branch offices, respectively. Both
have an identical VLAN tag for their VLAN group. The service provider can separate these
two VLANs within its network by adding tag 37 to distinguish customer A and tag 48 to
distinguish customer B at edge device 1 and then stripping those tags at edge device 2 as the
data frames leave the network.