
4.2.5 Encapsulation and Mapping Protocol
A bridge is a functional unit that is used to implement the interconnection between two or more
LANs.
4.2.1 Formats of Ethernet Frames
To implement the VLAN and QinQ functions, the IEEE 802.1q and IEEE 802.1ad protocols
define different formats of the Ethernet frames, which contain different VLAN information.
To implement the VLAN function, the IEEE 802.1q protocol defines the Ethernet frame format
that contains the VLAN information. Compared with the ordinary Ethernet frame, the frame
with the format defined by the IEEE 802.1q protocol is added with a four-byte header.
To implement VLAN mesting (QinQ), the IEEE 802.1ad protocol defines two VLAN tag types.
See
. The VLAN tag types are defined to differentiate the services on the client side
and the services on the supplier service side.
l
The VLAN tag used on the client side is represented as C-VLAN, of which the frame format
is the same as the frame format defined by the IEEE 802.1q protocol.
l
The VLAN tag used on the supplier service side is represented as S-VLAN.
4 Configuring Ethernet Services
OptiX OSN 550 Multi-Service CPE Optical Transmission
System
Configuration Guide
4-8
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Copyright © Huawei Technologies Co., Ltd.
Issue 02 (2011-06-30)