Tagging modes
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Overview
Sharing transport channels between multiple users requires the identification of MAC
frames. Tagging is the process of attaching an identifier, a “tag”, to a MAC frame in
order to identify the user to which the frame pertains.
These tagging modes are supported:
• Transparent tagging (“VPN tagging”)
• IEEE 802.1Q/IEEE 802.1ad VLAN tagging
– VLAN tagging compliant with IEEE 802.1Q-1998 (“IEEE 802.1Q VLAN
tagging”)
– VLAN tagging compliant with IEEE 802.1ad (“IEEE 802.1ad VLAN tagging”,
“Provider bridge tagging mode”)
The different tagging modes are explained later-on in this section.
Important! Note that it is not possible to use different tagging modes at the same
time on the same TransLAN
®
card.
However, within the transparent tagging mode there can be virtual switches in the
repeater mode, LAN interconnect mode, or LAN-VPN mode (with or without IEEE
802.1p QoS) at the same time on the same physical switch.
Transparent tagging
Transparent tagging (or “VPN tagging”) is a double tagging mode used to identify
end-user frames in the LAN-VPN mode of operation.
Selecting the transparent tagging mode implicitly means that the port role of the ports
is fixed. LAN ports are always customer-role ports, and WAN ports are always
network-role ports (see “Flexible port role assignment” (p. 8-77)).
To enable bandwidth sharing, a customer identification (CID) is associated with every
LAN port. This CID is inserted into incoming Ethernet frames, in an extra tag. MAC
address filtering and learning is done independently for every CID.
Ethernet frames that are already tagged become double tagged. Already present
end-user VLAN tags remain unused in the transparent tagging mode, i.e. every VLAN
tag is transmitted transparently through the SDH network.
Outgoing frames are only transmitted on LAN ports which have the respective CID
associated. The extra tag is removed before the Ethernet frames are forwarded to an
external LAN.
Note that in the VPN tagging mode the term “LAN group” is synonymously used to
the term “virtual switch”.
Traffic provisioning
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8-68
Alcatel-Lucent - Proprietary
See notice on first page
365-312-807R7.2
Issue 4, May 2007
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