H3C Technologies H3C SR8800 - Manual (Page 202)

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CCC MPLS L2VPN
Unlike common MPLS L2VPN, CCC employs just one level of label to transfer user data. Therefore, it uses
label switched paths (LSPs) exclusively. A CCC LSP can transfer only the data of the CCC connection; it
can neither be used for other MPLS L2VPN connections, nor for MPLS L3VPN or common IP packets.
The most significant advantage of this method is that no label signaling is required for transferring Layer
2 VPN information. As long as MPLS forwarding is supported and service provider networks are
interconnected, this method works perfectly. In addition, since LSPs are dedicated, this method supports
QoS services.
There are two types of CCC connections:
• Local connection—A local connection is established between two local CEs that are connected to
the same PE. The PE functions like a Layer 2 switch and can directly switch packets between the CEs
without any static LSP.
• Remote connection—A remote connection is established between a local CE and a remote CE,
which are connected to different PEs.
NOTE:
You must configure for each remote CCC connection two LSPs, one for inbound and the other for
outbound, on the P router along the remote connection.
SVC MPLS L2VPN
SVC also implements MPLS L2VPN by static configuration. It transfers L2VPN information without using
any signaling protocol.
The SVC method resembles the Martini method closely and is in fact a static implementation of the
Martini method. The difference is that it does not use LDP to transfer Layer 2 VC and link information. You
only need to configure VC label information.
NOTE:
The labels for CCC and SVC range from 16 to 1023, which are reserved for static LSPs.
Martini MPLS L2VPN
The key of the Martini method is to set up VCs between CEs.
Martini MPLS L2VPN employs VC type and VC ID to identify a VC. The VC type indicates the
encapsulation type of the VC, which can be ATM, VLAN, or PPP. The VC ID uniquely identifies the VC
among the VCs of the same type on a PE.
The PEs connecting the two CEs of a VC exchange VC labels through LDP, and bind their respective CE
by the VC ID.
Once LDP establishes an LSP between the two PEs and the label exchange and the binding to CE are
finished, a VC is set up and ready to transfer Layer 2 data.
To allow the exchange of VC labels between PEs, the Martini method extended LDP by adding the
forwarding equivalence class (FEC) type of VC FEC. Moreover, as the two PEs exchanging VC labels may
not be connected directly, a remote LDP session must be set up to transfer the VC FEC and VC labels.
With Martini MPLS L2VPN, only PEs need to maintain a small amount of VC labels and LSP mappings
and no P router contains Layer 2 VPN information. Therefore, it has high scalability. In addition, to add
a new VC, you only need to configure a one-way VC for each of the PEs. Your configuration will not affect
the operation of the network.