3Com S7906E - Switch, Руководство по настройке

Страница: 328 / 2621

4-3
of whether the Ethernet packets contain VLAN tags or not) to the OLT without changing them. Downlink
Ethernet packets are also forwarded transparently.
Table 4-2 describes the detailed packet processing
in this mode.
Tag mode
Tag mode is suitable for situations where the VLAN tags generated by the user-end family gateway or
switch are not trusted. To enable the operator to centrally manage and control the VLANs of the service
packets entering the network, network-layer VLAN tags need to be added to the packets.
Table 4-2
describes the detailed packet processing in this mode.
Translation mode
In translation mode, an ONU translates the VLAN tag added by the user (The user's VID may not be for
the user only, as some other users in the same EPON system may also use the same VID) into a unique
network-side VLAN tag.
Table 4-2 describes the packet processing by an ONU in translation mode.
Table 4-2
Packet processing in the three VLAN operation modes
VLAN
operation
mode
Direction
With or without
VLAN tag
Packet processing
With VLAN tag
Uplink
Without VLAN tag
With VLAN tag
Transparent
mode
Downlink
Without VLAN tag
The packet is forwarded without any change.
With VLAN tag The packet is dropped.
Uplink
Without VLAN tag
The packet is tagged with the VLAN tag
corresponding to the PVID and is then
forwarded.
With VLAN tag
The packet is forwarded to the corresponding
UNI port according to the VLAN ID and is
then untagged.
Tag mode
Downlink
Without VLAN tag The packet is dropped.