H3C Technologies H3C Intelligent Management Center - Manual (Page 88)

• VSI (Virtual Switch Instance)—Virtual switch instance that maps actual VPLS access links to virtual
links. As shown in the above figure, to ensure connectivity between devices, PE 1 and PE 2 are
configured with a VSI respectively, and the VSI ID is 1.
• PW (Pseudo Wire)—A pseudo wire is the bidirectional virtual connection between two VSIs. A
pseudo wire consists of two unidirectional virtual circuits (VCs).
• AC (Attachment Circuit)—Attachment circuit that connects a CE to a PE. It can use physical
interfaces or virtual interfaces.
• Tunnel—A tunnel, usually an MPLS tunnel, used to carry one or more PWs. It is a direct channel
between a local PE and the peer PE for transparent transmission in-between.
A typical H-VPLS network involves the following basic concepts:
• UPE (User Facing-Provider Edge)— User facing provider edge device that functions as the user
access convergence device.
• NPE (Network Provider Edge)—Network provider edge device that functions as the network core PE.
An NPE resides at the edge of a VPLS network core domain and provides transparent VPLS
transport services between core networks.
• U-PW—PW link between a UPE and an NPE.
• N-PW—PW link between two NPEs.
VPLS VPN types
• LDP VPN—Uses the Label Distribution Protocol (LDP) to establish virtual circuits by establishing
point-to-point sessions between a pair of PEs.
• BGP VPN—Uses the Border Gateway Protocol (BGP) to establish signaling sessions through route
reflectors (RRs) and supports networking across ASs.
Operation of VPLS
VPLS operation includes these elements:
• L2-pdu—Data link layer packet.
• Dmac—MAC address of the next hop device.
• Smac—MAC address of the local device.
• L—Public network label.
• V—Private network label.
• L'—Public network label after the packet is forwarded along the LSP.
Data forwarding procedure:
1. A PE receives a data packet from a CE through the AC. According to the VSI, the PE pushes its own
MAC address, the MAC address of the next hop, the public network label, and the private network
label into the packet. Then the PE forwards the packet to the core network according to the address
of the next hop.
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