PIM Relay Mode for Multicast Traffic Control
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Solution Overview
Problem
In virtual private local area network services (VPLS), the flooding of PIM control messages on all ports leads to excessive control traffic, triggering join suppression and requiring maintenance of upstream states and periodic timers, which complicates the management of multicast traffic.
Innovation Solution
Implementing a PIM relay mode in provider edge devices, where PIM control messages are relayed only on upstream neighbor ports, avoiding flooding on all ports and the construction of new messages, thus preventing join suppression and eliminating the need for upstream state maintenance and periodic timers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PIM control messages are flooded on all ports of PE devices, then multicast traffic can be delivered to all potential receivers, but excessive control traffic is generated and join suppression is triggered
Solution Approach 1:
The patent applies local quality by differentiating the treatment of PIM control messages based on port direction. Instead of uniform flooding on all ports, the system selectively relays messages only on upstream neighbor ports while avoiding downstream ports connected to PIM neighbor devices with receivers. This localized differentiation reduces control traffic harmfully while preserving necessary multicast delivery functionality.
2Reliability
If PIM control messages are flooded on all ports, then all potential receivers can receive multicast traffic, but upstream states must be maintained and periodic timers must be set
Solution Approach 1:
The patent extracts and eliminates the complex state maintenance and timer management requirements by changing the message forwarding approach. Instead of flooding on all ports which requires tracking upstream states and setting periodic timers, the invention relays messages only on upstream neighbor ports, removing the need for these complex mechanisms while maintaining reliable multicast delivery.
3Object-generated harmful factors
If PIM control messages are relayed only on upstream neighbor ports, then control traffic is reduced and join suppression is avoided, but message forwarding becomes more selective
Solution Approach 1:
The patent applies segmentation by dividing the port set into distinct categories: upstream neighbor ports versus downstream ports connected to PIM neighbor devices with receivers. This segmentation enables selective relaying of PIM control messages only on upstream ports, reducing control traffic and avoiding join suppression while providing clear operational rules for message forwarding.
Data Source
AI summary
Techniques are described for operating a network switch device associated with a virtual layer two (L2) network instance according to a protocol independent multicast (PIM) relay mode. The PIM relay mode enables the network switch device to receive a PIM control message, i.e., a PIM join and/or prune request, for a multicast group on a downstream port of the network switch device associated with a virtual L2 network instance, determine an upstream neighbor port of the network switch device associated with the instance, and relay the PIM control message on the upstream neighbor port of the network switch device without flooding the PIM control message on all ports of the switch device associated with the instance. In the PIM relay mode, the network switch device avoids triggering join suppression in downstream PIM neighbor devices with receivers, and avoids maintaining upstream states and setting a PIM periodic message timer.