Protected VTEP Address for BUM Traffic Node Failure
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Solution Overview
Problem
In multi-homed Ethernet Virtual Private Networks (EVPN) over VXLAN, node failures lead to traffic black-holing due to the time-consuming global repair process, where backup designated forwarders (BDFs) are not immediately activated to forward Broadcast, Unknown Unicast, and Multicast (BUM) traffic.
Innovation Solution
Each provider edge (PE) device advertises protected virtual tunnel endpoint (VTEP) addresses to other PE devices, allowing ingress PE devices to send BUM packets with these addresses in case of a failure, enabling backup PE devices to forward traffic even before global repair is complete, thus reducing traffic loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the global repair process is used to handle node failure in multi-homed EVPN, then the network can restore normal operation, but traffic black-holing occurs during the repair time causing packet loss
Solution Approach 1:
The patent pre-configures backup PE devices with backup forwarding entries before failure occurs. When a node failure is detected, the backup PE device can immediately activate these pre-prepared forwarding entries to forward BUM traffic, eliminating the need to wait for the global repair process to complete. This preliminary preparation of backup forwarding paths resolves the contradiction by enabling immediate traffic restoration without time loss.
2Reliability
If backup PE devices wait for global repair completion before forwarding traffic, then proper DF election can occur, but traffic black-holing occurs causing packet loss
Solution Approach 1:
The patent pre-configures backup PE devices with backup forwarding entries that include the ESI and protected VTEP address before failure occurs. These entries are prepared in advance but remain inactive during normal operation. Upon failure detection, the backup PE device can immediately activate these pre-prepared entries to forward traffic, resolving the contradiction between maintaining correct DF election procedures and ensuring continuous traffic forwarding.
Solution Approach 2:
The patent introduces protected VTEP addresses as an intermediary mechanism. The protected VTEP address is embedded in the backup forwarding entries to identify which node is being protected. This intermediary allows the backup PE device to distinguish between traffic that should be forwarded during failure conditions versus normal operation, enabling selective activation of backup paths without disrupting the standard DF election process.
3Productivity
If backup PE devices are immediately activated upon failure detection, then traffic forwarding continuity is maintained, but the global repair process may be bypassed causing incorrect DF election
Solution Approach 1:
The patent uses protected VTEP addresses as an intermediary to control backup forwarding activation. The protected VTEP address is specifically configured to match the failing node's address, creating a precise condition for activation. This intermediary mechanism ensures that backup forwarding is activated only when the correct node fails, preventing incorrect activation while maintaining traffic continuity. The global repair process can still proceed independently to ensure correct DF election.
Solution Approach 2:
The patent implements local quality by making backup forwarding entries specific to individual protected nodes through the protected VTEP address. Each backup PE device has customized backup entries tailored to the specific node it protects, rather than generic backup paths. This node-specific configuration ensures that backup activation is locally controlled and precise, maintaining both traffic continuity and DF election correctness.
Data Source
AI summary
Techniques are described for facilitating node protection for Broadcast, unknown Unicast, and Multicast (BUM) traffic for a multi-homed node failure. For example, each VTEP (e.g., PE device) may advertise a protected VTEP address that indicates an IP address of a remote PE device that is to be protected in the event of a node failure. In the event a multi-homed PE device fails, the ingress PE device sends a BUM packet including the protected VTEP address for the failed node. When an egress PE device receives the BUM packet, the egress PE device determines whether the BUM packet includes the protected VTEP address and whether the egress PE device is operating as a backup designated forwarder (DF). If the BUM packet includes the protected VTEP address and the egress PE device is a backup DF, the egress PE device forwards the BUM traffic to the ESI.