Layer 2 Topology Multipath Services via VLAN Aggregation
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Solution Overview
Problem
Conventional Layer 2 (L2) networks using Spanning Tree Protocol cannot provide multipath services for multicast frames due to their loop-free requirements, limiting the ability to send frames along Equal Cost Multipaths (ECMPs) and restricting path diversity for network traffic.
Innovation Solution
Implementing a link state protocol like IS-IS in the L2 network to create multiple paths for unicast and multicast frames, enabling ECMP for unicast and multipath services for multicast by aggregating Virtual Local Area Networks (VLANs) into topologies, allowing forwarding of packets on selected paths based on VLAN associations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Spanning Tree Protocol is used to ensure loop-free trees in L2 networks, then network stability is maintained, but path diversity and multipath services are lost
Solution Approach 1:
The patent segments the L2 network into multiple independent spanning tree instances (STP instances), where each instance maintains loop-free properties independently. This allows different VLANs or traffic types to be assigned to different STP instances, each with its own set of active paths, thereby achieving path diversity while maintaining reliability within each instance.
Solution Approach 2:
The patent introduces an additional dimension by creating multiple spanning tree instances rather than relying on a single STP instance. This dimensional expansion allows the network to provide multipath services by distributing traffic across different STP instances, each offering distinct paths while maintaining individual loop-free guarantees.
2Reliability
If STP-based trees are used for multicast forwarding, then loop-free forwarding is ensured, but Equal Cost Multipath (ECMP) services cannot be provided
Solution Approach 1:
The patent segments multicast forwarding into multiple STP instances, where each instance can independently forward multicast traffic along its own loop-free tree. This segmentation enables ECMP services by allowing multicast traffic to be distributed across multiple STP instances, each providing reliable loop-free forwarding while collectively offering multipath capabilities.
Solution Approach 2:
The patent makes STP instances universal by designing them to handle both unicast and multicast traffic within the same instance. This multi-functionality allows a single STP instance to provide both loop-free unicast forwarding and loop-free multicast forwarding, while the system as a whole provides ECMP services through multiple such instances.
3Ease of operation
If VLAN-specific forwarding tables are maintained in L2 networks, then precise VLAN control is achieved, but hardware requirements and complexity increase
Solution Approach 1:
The patent merges multiple VLAN-specific forwarding tables into a single aggregated forwarding table that operates at the STP instance level rather than individual VLAN level. This consolidation reduces hardware requirements by eliminating the need to maintain separate forwarding state for each VLAN, while still providing precise VLAN control through the mapping of VLANs to specific STP instances.
Solution Approach 2:
The patent creates a universal forwarding table that serves multiple VLANs through a single STP instance. This forwarding table performs multiple functions by handling forwarding decisions for all VLANs mapped to that instance, thereby reducing hardware complexity while maintaining the ability to provide differentiated services to individual VLANs through instance-level policies.
Data Source
AI summary
In one embodiment, a method includes receiving information on layer 2 topologies at a network device in a core network, mapping one or more Virtual Local Area Networks (VLANs) to the layer 2 topologies to provide differentiated services in said layer 2 topologies, defining multiple paths for each of the layer 2 topologies, and forwarding a packet received at the network device on one of the multiple paths. An apparatus and logic for providing differentiated services in layer 2 topologies is also disclosed.