The Nokia implementation also alternative methods for providing a redundant access to Layer 2 services, such as MC-LAG. Also in this case, the topology change event needs to be propagated into VPLS topology to provide fast convergence.
Figure: H-VPLS with spoke redundancy show a dual-homed connection to VPLS service (PE-A, PE-B, PE-C, PE-D) and operation in case of link failure (between PE-C and L2-B). Upon detection of a link failure PE-C sends MAC-Address-Withdraw messages, which indicates to all LDP peers that they should flush all MAC addresses learned from PE-C. This leads to a broadcasting of packets addressing affected hosts and relearning process in case an alternative route exists.
Note that the message described here is different from the message described in previous section and in RFC 4762, Virtual Private LAN Services Using LDP Signaling. The difference is in the interpretation and action performed in the receiving PE. According to the standard definition, upon receipt of a MAC withdraw message, all MAC addresses, except the ones learned from the source PE, are flushed,
This section specifies that all MAC addresses learned from the source are flushed. This message has been implemented as an LDP address message with vendor-specific type, length, value (TLV), and is called the flush-mine message.
The advantage of this approach (as compared to RSTP based methods) is that only MAC-affected addresses are flushed and not the full forwarding database. While this method does not provide a mechanism to secure alternative loop-free topology, the convergence time is dependent on the speed of the specific CE device opening alternative links (L2-B switch in Figure 57) as well as on the speed PE routers flush their FDB.
In addition, this mechanism is effective only if PE and CE are directly connected (no hub or bridge) as it reacts to physical failure of the link.