Multicast Control Plane Signaling for L2VPN Redundancy
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Solution Overview
Problem
In layer 2 virtual private networks, multicast traffic forwarding is hindered by the need for network devices to snoop IGMP traffic after a primary attachment circuit failure, leading to blackholing of multicast traffic until an IGMP refresh occurs, and redundant IGMP traffic is sent unnecessarily.
Innovation Solution
A customer edge device proactively sends a control plane message to a backup provider edge device to configure multicast forwarding state, enabling rapid switchover and reducing blackholing by explicitly indicating interested hosts for multicast groups, thus avoiding unnecessary snooping and redundant traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the backup provider edge device waits to snoop IGMP traffic after primary circuit failure, then it can dynamically learn multicast group information, but multicast traffic is blackholed until IGMP refresh occurs causing service interruption
Solution Approach 1:
The backup provider edge device performs preliminary actions by proactively receiving control plane messages from customer edge devices before the primary attachment circuit fails. This allows the backup device to pre-configure multicast forwarding state and be ready to immediately assume traffic forwarding upon failure, eliminating the blackholing period that would otherwise occur while waiting for IGMP refresh traffic.
Solution Approach 2:
A control plane message acts as an intermediary mechanism between the customer edge device and the backup provider edge device. This message carries multicast group information and enables the backup device to learn about interested hosts without needing to snoop IGMP traffic in the data plane, thus resolving the contradiction by providing an alternative information channel.
2Loss of information
If the customer edge device sends IGMP traffic to the backup provider edge device, then the backup device can learn about interested hosts, but redundant signaling traffic is generated unnecessarily
Solution Approach 1:
The invention extracts the essential information (multicast group membership) from the IGMP traffic and transfers it through a control plane message. This separates the control information from the data plane IGMP traffic, allowing the backup provider edge device to learn about interested hosts without requiring the customer edge device to send redundant IGMP messages through the backup attachment circuit.
Solution Approach 2:
The control plane message serves as an intermediary that efficiently conveys multicast group information from the customer edge device to the backup provider edge device. This intermediary mechanism eliminates the need for redundant IGMP signaling traffic while ensuring the backup device receives accurate information about interested hosts.
Data Source
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AI summary
In some examples, a customer edge device (CE) is configured to receive configuration data for multi-homed connectivity for a local layer 2 (L2) network with a L2 virtual private network (L2VPN) for a layer 3 (L3) network for switching L2 packet data units (PDUs) among two or more L2 networks connected to the L3 network including the local L2 network, wherein the configuration data for multi-homed connectivity configures the CE with a primary attachment circuit to a primary neighbor provider edge device (PE) for the L2VPN and with a backup attachment circuit to a backup neighbor PE for the L2VPN; and generate and send, in response to snooping a multicast join message indicating a multicast group, a control plane message via the backup attachment circuit to the backup neighbor PE for the L2VPN, wherein the control plane message is destined for the backup neighbor PE for the L2VPN.