EVPN Multihomed Peer Protection Label for Loop Avoidance
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Solution Overview
Problem
In Ethernet VPN (EVPN) networks with multihomed connections, existing fast reroute mechanisms can cause looping when both PE links fail, leading to network degradation and potential failure due to the inability to distinguish between fast reroute traffic and normal unicast traffic.
Innovation Solution
The introduction of a multihomed peer protection (MPP) label allows the protector egress PE to differentiate between fast reroute traffic and normal unicast traffic, enabling it to discard or route traffic appropriately to prevent looping by allocating and advertising specific labels for known unicast and MPP traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fast reroute mechanisms are implemented in EVPN networks with multihomed connections, then network reliability is improved through backup link protection, but looping occurs when both PE links fail causing network degradation
Solution Approach 1:
The patent introduces a Multihomed Peer Protection (MPP) label as an intermediary mechanism to mediate between fast reroute traffic and normal unicast traffic. This MPP label acts as a mediator that enables the protector egress PE to identify and differentiate FRR traffic from regular unicast traffic, thereby preventing harmful looping while maintaining the reliability benefits of fast reroute protection
Solution Approach 2:
The patent applies local quality by assigning different label types (KU labels for normal unicast traffic and MPP labels for fast reroute traffic) to different traffic flows at specific network nodes. This differentiation at the local level enables precise control over traffic handling, allowing the protector egress PE to apply appropriate forwarding actions based on the specific label type encountered
2Reliability
If existing fast reroute mechanisms are used, then single link failure protection is achieved, but the inability to distinguish between fast reroute traffic and normal unicast traffic causes looping during double link failures
Solution Approach 1:
The patent changes the label parameter used in traffic forwarding by introducing a distinct MPP label type alongside existing KU labels. This parameter change in the labeling scheme enables the network to carry additional information about traffic origin and type, allowing the protector egress PE to distinguish between FRR and normal unicast traffic without losing the existing single link failure protection capabilities
Data Source
AI summary
The problem of looping at the egress of a transport network with a CE multihomed to a protected egress PE and a backup/protector egress PE can be avoided by (a) enabling the protector egress PE to distinguish between fast reroute (FRR) traffic coming from the protected egress PE and normal known unicast (KU) traffic coming from a PE of the transport network that is not attached to the same multihomed segment; (b) receiving, by the protector egress PE, known unicast data, to be forwarded to the CE; (c) determining, by the protector egress PE, that a link between it and the CE is unavailable; and (d) responsive to determining that the link between the protector egress PE and the CE is unavailable, (1) determining whether the known unicast traffic received was sent from the protected egress PE or from another PE of the transport network that is not attached to the same multihomed segment, and (2) responsive to a determination that the known unicast traffic received was sent from the protected egress PE, discarding the known unicast traffic received, and otherwise, responsive to a determination that the known unicast (KU) traffic received was sent from another PE of the transport network that is not attached to the same multihomed segment, sending the known multicast traffic, via a backup tunnel, to an egress PE which protects the protector egress PE.