325PEs. The PW type specifies the encapsulation type for data transmitted over the PW, such asEthernet or VLAN. PEs advertise the PW label and PW ID FEC in label mapping messages tocreate a PW. Dynamic PWs have simple configurations but consume more resources thanstatic PWs.To establish BGP PWs, BGP advertises label block information in an extended BGP update toPEs in the same VPN. Each PE uses the received label block information to calculate outgoinglabels and uses its own label block to calculate incoming labels. After two PEs complete labelcalculation, a BGP PW is established between them. BGP PWs have the following features: Simplified configuration—There is no need to manually specify peer PEs. A PEautomatically find peer PEs after receiving label block information from the peer PEs. Reduced workload—Label block advertisement enables assigning labels for multiple PWsat one time.To establish a CCC PW, manually specify the incoming and outgoing labels for the PW on thePEs, and create two static LSPs in opposite directions on P devices between PEs. There is noneed to configure a public tunnel for the CCC PW. CCC employs only one level of label totransfer packets. The static LSPs on the P devices transfer data only for the CCC PW. Theycannot be used by other connections or MPLS L3VPN.3. Set up an AC between a PE and a CE:Set up an AC by configuring a link layer connection between a PE and a CE.The AC can only be an Ethernet service instance on a Layer 2 Ethernet interface or Layer2 aggregate interface. It forwards packets that are received on the interface and meet thematch criteria of the Ethernet service instance to the bound PW. If the match criterion is VLANID, the VLAN is unique on a per interface basis rather than on a global basis.NOTE:When VLANs are globally unique, packets with the same VLAN ID are forwarded over the PWbound with that VLAN ID regardless of the receiving interfaces. If VLANs are unique on a perinterface basis, packets with the same VLAN ID from different interfaces can be forwarded overdifferent PWs.4. Bind the AC to the PW:Bind the Layer 3 physical interface, Layer 3 subinterface, or Ethernet service instance to thePW, so the PE forwards packets between the AC and the PW.PW typesMPLS L2VPN transports Layer 2 data of different data link layer protocols through PWs. A PEencapsulates a Layer 2 packet received from an AC according to the PW type. The PW type isdetermined by the link type of the AC, as shown in Table 30.Table 30 Relationship between AC types and PW typesAC type PW typeEthernet EthernetVLANEthernet over MPLS uses MPLS L2VPN to connect Ethernets, and delivers Ethernet packetsthrough a PW over the MPLS backbone.The following PW types are available for Ethernet over MPLS:• Ethernet—P-tag is not transferred on a PW. For a packet from a CE:
