Method for implementing a virtual leased line

A method for implementing a virtual leased line (VLL), comprising the steps of:

• configuring a virtual local area network (VLAN) label stack on the basis of VLAN QinQ;
• configuring a VLAN QinQ switching device and a multi-protocol label switching (MPLS) device to communicate with each other and implementing switching between VLAN labels and MPLS labels;
• extending a label distribution protocol (LDP) to support encapsulation of VLAN labels, so as to carry out VLAN label assignment and take the extended LDP as a topology discovery protocol for an L2 virtual private network;
• setting the range of VLAN labels;
• implementing a VLL by constructing a VLAN switching path;
• wherein the step of configuring the VLAN QinQ switching device and the MPLS device to communicate with each other further comprises the sub-steps of:
• if the VLAN QinQ switching device is at upstream, accomplishing conversion from VLAN QinQ encapsulation to MPLS encapsulation at an outgoing interface of the VLAN QinQ switching device;
• if the VLAN QinQ switching device is at downstream,
• assigning a MPLS label with the same range as VLAN labels to the upstream MPLS device by the VLAN QinQ switching device, identifying the MPLS label at the incoming interface of the VLAN QinQ switching device, and treating the label as a VLAN label, with the upstream MPLS device not modified;
• or
• assigning a VLAN label to the upstream MPLS device by the VLAN QinQ switching device, with the upstream MPLS device modified to support the VLAN QinQ encapsulation.