Virtual Private LAN Services
7210 SAS M Services Guide Page 441
PBB Technology
IEEE 802.1ah specification encapsulates the customer or QinQ payload in a provider header as
shown in Figure 60.
Figure 60: QinQ Payload in Provider Header Example
PBB adds a regular Ethernet header where the B-DA and B-SA are the backbone destination and
respectively, source MACs of the edge U-PEs. The backbone MACs (B-MACs) are used by the
core N-PE devices to switch the frame through the backbone.
A special group MAC is used for the backbone destination MAC (B-DA) when handling an
unknown unicast, multicast or broadcast frame. This backbone group MAC is derived from the I-
service instance identifier (ISID) using the rule: a standard group OUI (01-1E-83) followed by the
24 bit ISID coded in the last three bytes of the MAC address.
The BVID (backbone VLAN ID) field is a regular DOT1Q tag and controls the size of the
backbone broadcast domain.
The following ITAG (standard Ether-type value of 0x88E7) has the role of identifying the
customer VPN to which the frame is addressed through the 24 bit ISID.
Payload
Ethertype
Ethertype
Ethertype
802.1ad
22B
(No FCS/Preamble)
Ethertype
2-4
1
8 654321
1
2-4 5-10 11-16
I-SID
I-PCP Res2
I-DEI
Res1
NCA
C-DA C-SA
2+2
Octets
Bits
6+6
Ethertype
C-VID
S-VID
I-TAG
C-SA
C-DA
B-SA
B-VID
B-DA
OSSG192
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