Split-Horizon Packet Forwarding in Multi-Homed PBB-EVPN
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Solution Overview
Problem
In multi-homed Provider Backbone Bridging Ethernet Virtual Private Networks (PBB-EVPN), packets originating from a customer network can be inadvertently replicated back to the customer network due to the lack of effective split-horizon forwarding mechanisms, leading to traffic loops and inefficiencies.
Innovation Solution
Implementing split-horizon packet forwarding techniques by designating a PE device as a designated forwarder, which determines the ingress interface of received packets and applies split-horizon forwarding rules to prevent packet replication, ensuring that packets injected into the PBB-EVPN by one PE device are not forwarded back to the customer network by another PE device connected to the same Ethernet segment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-homed CE device is connected to multiple PE devices for redundancy, then network reliability is improved, but packet replication and traffic loops occur causing network instability
Solution Approach 1:
The invention segments the forwarding decision process by introducing a designated forwarder (DF) election mechanism among PE devices. Each Ethernet segment is divided into distinct forwarding responsibilities, where only the elected DF forwards packets from that segment into the EVPN, preventing multiple PE devices from forwarding the same packet and thus eliminating packet replication and traffic loops.
Solution Approach 2:
The invention applies local quality by making each PE device's forwarding behavior dependent on its local role assignment. The DF election assigns different forwarding privileges to different PE devices based on their local status (DF or non-DF), allowing packets to be forwarded reliably while preventing any single non-DF device from replicating packets intended for other segments.
2Productivity
If packets are forwarded through multiple PE devices for load distribution, then network throughput is improved, but packet replication occurs leading to traffic inefficiency
Solution Approach 1:
The invention performs preliminary action by establishing DF election and ingress interface identification before packet forwarding occurs. The PE device identifies the ingress interface from which the packet entered the EVPN and uses this information to determine whether forwarding should occur, preventing packet replication before it can consume network resources.
Solution Approach 2:
The invention implements feedback by using the ingress interface information to control forwarding decisions. The PE device receives packets, identifies their ingress interface, and uses this feedback to determine whether to forward the packet or drop it, ensuring that only appropriately routed packets are forwarded and eliminating unnecessary traffic replication.
3Stability of the object's composition
If split-horizon forwarding is implemented to prevent packet replication, then network stability is improved, but forwarding complexity increases
Solution Approach 1:
The invention applies self-service by enabling PE devices to automatically perform DF election and ingress interface identification without external control. Each PE device independently determines its DF status and uses its own ingress interface information to make forwarding decisions, reducing the need for complex centralized control mechanisms while maintaining network stability.
Data Source
AI summary
Techniques are described to provide split-horizon packet forwarding so as to ensure that packets from the customer network that are injected into the provider backbone bridging Ethernet Virtual Private Network (PBB-EVPN) by one of the provider edge (PE) devices of the multi-homed Ethernet segment are not forwarded back toward the customer network by a different PE device connected to the same multi-homed Ethernet segment. For example, a method may comprise receiving a packet via a core-facing interface of a first PE device, determining the Ethernet segment associated with the PE devices by a lookup operation based on keys of the packet; in response to determining the Ethernet segment, supplanting the core-facing interface of the first PE device with a virtual interface associated with the keys, and forwarding the packet to a second CE device without forwarding the received packet back to the Ethernet segment associated with the first PE device.