Samsung Ubigate iBG3026, Configuration Manual, Page: 257 / 718

Ubigate iBG3026 Configuration Guide/Ed.00
© SAMSUNG Electronics Co., Ltd.
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Virtual LAN Domain
The iBG3026 supports VLAN-based data forwarding. Essentially, this feature
forwards the packets from one network to another based on the VLAN
identifier(rather than routing) contained in the VLAN header, as defined by
IEEE 802.1q. The VLAN packets are generally termed as tagged packets
referring to the VLAN encapsulation of the Ethernet packets.
The iBG3026 also supports VLD(Virtual LAN Domain).
VLD allows a VLAN packet to be tagged with another level of VLAN header.
This is used by service providers to carry the subscriber’s VLAN packets
transparently through the provider’s VLAN network. The VLD packets are
generally termed as double tagged packets referring to the two levels of
VLAN encapsulation of the Ethernet packets.
Ethernet packets, arriving on an interface(say an Ethernet) configured for
VLD tagging, are also tagged(only one level) with the tag ID configured for
VLD tagging on that interface. These single level tagged VLAN packets can
now be forwarded on the trunk port(say a WAN interface) using the VLD
forwarding table itself. In the return path, packets arriving on the trunk port as
VLAN packets can be forwarded to the Ethernet interface(based on VLD
forwarding table) and when they exit through the Ethernet, they are untagged
one level(since this VLD tagged interface would have performed one level of
untagging anyway).
This enhancement allows users to handle two different types of subscriber
traffic on the same interface. One traffic type is the VLAN traffic generated by
the subscriber and typically meant for office-to-office communication through
a service provider network.
The other traffic type is the Ethernet traffic generated by the subscriber for
Internet access through the same service provider.
The management of Tasman routers through a VLAN remains unaffected due
to this enhancement.