H3C Technologies H3C S12500 Series Switches - Manual (Page 222)

209
Figure 77 shows the format of a MAC-in-MAC frame. Table 22 describes some key fields in the frame.
Table 22 Some key fields of a MAC-in-MAC frame
Field Full name Description
B-DA Backbone destination MAC address
Destination B-MAC, outer destination MAC address in a
MAC-in-MAC frame. It is the MAC address of the BEB device
at the destination end of the PBBN tunnel. The combination of
B-DA and B-SA is B-MAC.
B-SA Backbone source MAC address
Source B-MAC, outer source MAC address in a
MAC-in-MAC frame. It is the MAC address of the BEB device
at the source end of the PBBN tunnel. The combination of
B-DA and B-SA is B-MAC.
B-Tag Backbone VLAN tag
Outer VLAN tag in a MAC-in-MAC frame. It indicates the
VLAN information and priority information of the frame
within the PBBN. The Tag Protocol Identifier (TPID) in the
B-tag is 0x8100.
I-Tag Backbone service instance tag
Service identifier of a MAC-in-MAC frame. The I-tag contains
the backbone service instance priority code point (I-PCP) and
backbone service instance drop eligibility indicator (I-DEI) on
the BEB, backbone service instance identifier (I-SID), and the
C-DA and C-SA of the customer frame. The TPID of the I-tag is
0x88E7.
S-Tag Service provider VLAN tag
Outer VLAN tag of the frame in the PBN, which indicates the
VLAN information and priority information of the frame
within the PBN.
C-Tag Customer VLAN tag
Inner VLAN tag of the frame in the PBN, which indicates the
VLAN information and priority information of the frame
within the customer network.
For more information about TPID, see "Configuring VLANs."
MAC-in-MAC frame forwarding
Figure 78 MAC-in-MAC frame forwarding