NetComm NB712 manual Applications, VID uniquely identifies the Vlan to which the frame belongs

as belonging to a particular VLAN based on the value of the VID that is included in the tag header. The presence of the tag header carrying a non-null VID means that some other device, either the originator of the frame or a VLAN-aware bridge, has mapped this frame into a VLAN and has inserted the appropriate VID.

The following figure shows the difference between a untagged frame and VLAN tagged frame, where the Tag Protocol Identifier (TPID) is of 0x8100 and it identifies the frame as a tagged frame. The Tag Control Information (TCI) consists of the following elements:

1)User priority allows the tagged frame to carry user priority information across bridged LANs in which individual LAN segments may be unable to signal priority information (e.g., 802.3/Ethernet segments).

2)The Canonical Format Indicator (CFI) is used to signal the presence or absence of a Routing Information Field (RIF) field, and, in combination with the Non-canonical Format Indicator (NCFI) carried in the RIF, to signal the bit order of address information carried in the encapsulated frame.

3)The VID uniquely identifies the VLAN to which the frame belongs.

3.3Applications

SHDSL Router SHDSL Router

Ethernet SHDSL Ethernet

LAN LAN

		SHDSL Router
Internet			LAN
	SHDSL	Ethernet
	DSLAM

NB712 /	NB714 User Guide	13
YML829	Rev1