ZyXEL Communications MSC1000G Series, User Manual

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Chapter 9 Subscriber Port Setup Screens
Management Switch Card User’s Guide
209
9.2.11 RFI (Radio Frequency Interference)
RFI is induced noise on the lines by surrounding radio frequency electromagnetic radiation from
sources such as AM and HAM radio stations. Since VDSL uses a much larger frequency range that
overlaps with other radio frequency systems, signals from VDSL lines and other radio systems
interfere with each other. To avoid performance degradation due to RFI, set the switch to not
transmit VDSL signals in the RFI band defined by the regulatory bodies (ETSI and ANSI). You can
also configure your own RFI bands on the system.
9.2.12 Transparent LAN Service (TLS)
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 switch sends the frames from the customers, the VLAN ID is added to the frames. When
packets intended for specific customers are received on the MSC, the outer VLAN tag is removed
before the traffic is sent.
9.2.13 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.