User`s manual

Chapter 1 Overview
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This mode is available for both the external LAN ports (LAN 1 and LAN 2),
and for virtually concatenated groups 1 to 4.
 Untagged: all the frames egress the port as untagged frames. Therefore,
untagged frames egress the port unmodified, whereas tagged frames are
converted to untagged frames before egressing the port (this is
performed by removing their tag and recalculating the frame CRC). This
mode is available only for the virtually concatenated groups 1 to 4.
 Tagged: all the frames egress the port as tagged frames. Therefore,
tagged frames egress the port unmodified, whereas untagged frames are
converted to tagged frames before egressing the port (this is performed
by adding a tag with the VLAN ID which is defined for the corresponding
port, and recalculating the frame CRC). This mode is available only for
the virtually concatenated groups 1 to 4.
 Double tagged: a tag is always added to all the frames that egress the
port. This mode can be used only when the network supports a frame
size of at least 1526 bytes.
1.6.4 Ethernet Mapper Subsystem
The Ethernet mapper subsystem manages all the functions that are related to the
use of virtual concatenation, and the preparation of LAN traffic for efficient
transport via the SDH network.
The subsystem includes the following functions:
 LAPS encapsulation
 GFP encapsulation
 Group mapper
 GFP multiplexer
MUXpro unit also supports the Link Capacity Adjustment Scheme (LCAS),
covered by ITU-T Rec. G.7042.
1.6.4.1 Encapsulation Functions
Ethernet frames must be encapsulated before transporting over the SDH network.
Two types of encapsulation are supported: