Vlan Tag Format; Frame Format - ZyXEL Communications VES1724-56 User Manual

Chapter 23 VLAN Stacking

23.3 VLAN Tag Format

A VLAN tag (service provider VLAN stacking or customer IEEE 802.1Q) consists of the following
three fields.
Table 88 VLAN Tag Format
TPID
TPID (Tag Protocol Identifier) is a standard Ethernet type code identifying the frame and indicates
whether the frame carries IEEE 802.1Q tag information. The value of this field is 0x8100 as defined
in IEEE 802.1Q. Other vendors may use a different value, such as 0x9100.
Tunnel TPID is the VLAN stacking tag type the Switch adds to the outgoing frames sent through a
Tunnel Port of the service provider's edge devices (1 and 2 in the VLAN stacking example figure).
Priority refers to the IEEE 802.1p standard that allows the service provider to prioritize traffic
based on the class of service (CoS) the customer has paid for.
• On the Switch, configure priority level of inner IEEE 802.1Q tag in the Port Setup screen.
• "0" is the lowest priority level and "7" is the highest.
VID is the VLAN ID. SP VID is the VID for the second (service provider's) VLAN tag.

23.3.1 Frame Format

The frame format for an untagged Ethernet frame, a single-tagged 802.1Q frame (customer) and a
"double-tagged" 802.1Q frame (service provider) is shown next.
Configure the fields as highlighted in the Switch VLAN Stacking screen.
Table 89 Single and Double Tagged 802.11Q Frame Format
DA SA Tunnel
TPID
Table 90 802.1Q Frame
DA
SA
Tunnel TPID
VID
210
Priority VID
DA SA TPID Priority VID
Priorit VID TPID Priority VID
y
Destination Address
Source Address
Tag Protocol IDentifier added on a tunnel port
VLAN ID
DA SA Len/Etype Data
Len/Etype Data
Len/Etype Data
Priority
Len/Etype Length and type of Ethernet frame
Data
FCS
FCS Untagged
Ethernet frame
FCS IEEE 802.1Q
customer
tagged frame
FCS Double-tagged
frame
802.1p Priority
Frame data
Frame Check Sequence
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