ID (12 bits) Identification - customer identification which can be configured
in the range [0 { 4093].
Concerning their structure there is no difference between a VLAN tag (C-tag) and a
CID tag (S-tag). A distinction between both types of tags can be made by means of the
value in the TPID field, the “Ethertype”. In the IEEE 802.1ad VLAN tagging mode
(provider bridge tagging mode), the Ethertype can be provisioned per virtual switch.
The value of the Ethertype depends on the mode of operation:
• In the transparent tagging modes (VPN tagging modes), the value of the Ethertype
is 0xFFFF, and cannot be changed.
• In the IEEE 802.1Q VLAN tagging mode, the value of the Ethertype is 0x8100,
and cannot be changed.
• In the IEEE 802.1ad VLAN tagging mode (provider bridge tagging mode), the
value of the Ethertype can be flexibly chosen in the range 0x0601 { 0xFFFF, but
unequal to 0x8100. The recommended value for the Ethertype in the provider
bridge tagging mode is 0x9100.
Comparison of different tagging schemes
The next figure summarizes the possible tagging schemes:
• No tagging
• Single tagging (IEEE 802.1Q VLAN tagging)
• Double tagging (VPN tagging, IEEE 802.1ad VLAN tagging)
IPG
Bytes: 12 (min.) 7
1
6 6 2 46 - 1500 4
Preamble SFD DA SA
L / T
Data FCS
IPG
Bytes: 12 (min.) 7
1
6 6 46 - 15004
Preamble SFD DA SA Data FCS
2
L / TVLAN
4
46 - 15004
Data FCS
2
L / TVLAN
44
CID
66
DA SA
No tagging
Single tagging
Double tagging
Traffic provisioning
Tagging modes
....................................................................................................................................................................................................................................
8-72
Alcatel-Lucent - Proprietary
See notice on first page
365-312-807R7.2
Issue 4, May 2007
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