L2VPN Multicast Snooping via Edge Marking
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Solution Overview
Problem
In network systems using the IEEE 802.1ah protocol for forming L2VPN, core switches fail to recognize join messages encapsulated in MAC-in-MAC frames, leading to multicast packet flooding across the core network, which reduces communication rates.
Innovation Solution
The network system includes a core switch and an edge switch with specific units for identifying and marking join messages, allowing the core switch to associate input/output ports with multicast groups through snooping of mark information, thereby preventing multicast packet flooding by correctly routing MAC-in-MAC frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MAC-in-MAC frame forwarding is implemented in the core network, then L2VPN functionality is achieved, but core switches cannot recognize join messages leading to multicast packet flooding
Solution Approach 1:
The patent introduces an intermediary mechanism where the edge switch adds mark information to MAC-in-MAC frames containing join messages. This mark acts as a mediator that enables core switches to identify and properly handle multicast join messages without requiring them to understand the encapsulated IGMP/MLD protocols, thus preventing flooding while maintaining L2VPN functionality.
Solution Approach 2:
The patent segments the multicast message handling function between edge switches and core switches. Edge switches perform the complex task of identifying and marking join messages, while core switches perform the simpler task of reading marks and forwarding. This segmentation allows core switches to handle L2VPN traffic without needing full multicast protocol awareness.
2Reliability
If core switches flood multicast packets across the network, then all switches receive multicast traffic, but communication rate in L2VPN is reduced
Solution Approach 1:
The patent applies preliminary action by having edge switches mark MAC-in-MAC frames containing join messages before they enter the core network. This pre-marking enables core switches to identify multicast traffic intent in advance and perform selective forwarding, preventing unnecessary flooding and maintaining high communication rates while ensuring reliable multicast delivery to intended recipients.
3Measurement precision
If core switches perform snooping on encapsulated IGMP/MLD messages, then join messages can be recognized, but the complexity of message identification increases
Solution Approach 1:
The mark information serves as an intermediary that simplifies the identification process. Instead of requiring core switches to perform complex snooping on encapsulated IGMP/MLD messages, the edge switch adds a simple mark that the core switch can read directly from the MAC-in-MAC frame header, significantly reducing identification complexity while maintaining precise join message recognition.
Data Source
AI summary
A network system includes: a core switch; and an edge switch. The edge switch includes: a join message identification unit; and a marking unit. The join message identification unit identifies a join message from among MAC frames from the user network. The marking unit marks mark information to a header of a MAC-in-MAC frame in which the identified join message is encapsulated. The core switch includes: a plurality of input/output ports; a mark identification unit; and a port setup unit. The mark identification unit identifies a MAC-in-MAC frame to whose a header the mark information is marked. The port setup unit associates a multicast group of a join message which is encapsulated in the identified MAC-in-MAC frame, with an input/output port to which the identified MAC-in-MAC frame is input.