Vlan Tag Format; Frame Format; Table 47 Vlan Tag Format; Table 48 Single And Double Tagged 802.11Q Frame Format - ZyXEL Communications GS-2724 User Manual

21.3 VLAN Tag Format

A VLAN tag (service provider VLAN stacking or customer IEEE 802.1Q) consists of the
following three fields.

Table 47 VLAN Tag Format

Type
Type is a standard Ethernet type code identifying the frame and indicates that whether the
frame carries IEEE 802.1Q tag information. SP TPID (Service Provider Tag Protocol
Identifier) is the service provider VLAN stacking tag type. Many vendors use 0x8100 or
0x9100.
TPID (Tag Protocol Identifier) is the customer IEEE 802.1Q tag.
• If the VLAN stacking port role is Access Port, then the Switch adds the SP TPID tag to
all incoming frames on the service provider's edge devices (1 and 2 in the VLAN stacking
example figure).
• If the VLAN stacking port role is Tunnel Port, then the Switch only adds the SP TPID
tag to all incoming frames on the service provider's edge devices (1 and 2 in the VLAN
stacking example figure) that have an SP TPID different to the one configured on the
Switch. (If an incoming frame's SP TPID is the same as the one configured on the Switch,
then the Switch will not add the tag.)
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.

21.3.1 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 circled in the Switch's VLAN Stacking screen.

Table 48 Single and Double Tagged 802.11Q Frame Format

DA SA SPTPI
D

Table 49 802.1Q Frame

DA Destination Address
SA Source Address
(SP)TPID (Service Provider) Tag Protocol IDentifier
VID VLAN ID
GS-2724 User's Guide
Priority VID
DA
DA SA TPID Priorit
y
Priority VID TPID Priorit
y
Chapter 21 VLAN Stacking
SA Len/ Data FCS Untagged
Etype
VID Len/ Data FCS IEEE 802.1Q
Etype
VID Len/ Data FCS Double-tagged
Etype
Priority 802.1p Priority
Len/ Length and type of Ethernet frame
Etype
Data Frame data
FCS Frame Check Sequence
Ethernet frame
customer
tagged frame
frame
149