Ubigate iBG2016 Configuration Guide/Ed.00© SAMSUNG Electronics Co., Ltd. 231Virtual LAN DomainThe iBG2016 supports VLAN-based data forwarding. Essentially, this featureforwards the packets from one network to another based on the VLANidentifier(rather than routing) contained in the VLAN header, as defined byIEEE 802.1q. The VLAN packets are generally termed as tagged packetsreferring to the VLAN encapsulation of the Ethernet packets.The iBG2016 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 packetstransparently through the provider’s VLAN network. The VLD packets aregenerally termed as double tagged packets referring to the two levels ofVLAN encapsulation of the Ethernet packets.Ethernet packets, arriving on an interface(say an Ethernet) configured forVLD tagging, are also tagged(only one level) with the tag ID configured forVLD tagging on that interface. These single level tagged VLAN packets cannow be forwarded on the trunk port(say a WAN interface) using the VLDforwarding table itself. In the return path, packets arriving on the trunk port asVLAN packets can be forwarded to the Ethernet interface(based on VLDforwarding table) and when they exit through the Ethernet, they are untaggedone level(since this VLD tagged interface would have performed one level ofuntagging anyway).This enhancement allows users to handle two different types of subscribertraffic on the same interface. One traffic type is the VLAN traffic generated bythe subscriber and typically meant for office-to-office communication througha service provider network.The other traffic type is the Ethernet traffic generated by the subscriber forInternet access through the same service provider.The management of Tasman routers through a VLAN remains unaffected dueto this enhancement.
