TRILL Transient Appointed Forwarder for Rapid Network Convergence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The Transparent Interconnect of Lots of Links (TRILL) protocol faces limitations in convergence speed and determinism due to sequential convergence with Spanning Tree Protocol (STP) and the use of a root change inhibition timer, leading to potential looping issues in network topology changes.
Innovation Solution
Implementing a transient appointed forwarder mechanism that assigns a temporary forwarder between STP and TRILL convergence, using a pseudo root bridge identifier and Time-Length-Value (TLV) in Hello protocol messages, and integrating Layer 2 Gateway Port (L2GP) to facilitate rapid TRILL convergence by allowing frame forwarding during this period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the root change inhibition timer is set longer to prevent looping, then reliability is improved, but convergence speed deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-assigning a transient appointed forwarder before the root change inhibition timer expires. This transient AF is designated in advance to handle forwarding during the convergence period, allowing traffic to flow immediately after topology changes without waiting for the full timer duration, thus maintaining reliability while reducing convergence time.
Solution Approach 2:
The transient appointed forwarder acts as an intermediary between the STP convergence and the TRILL convergence. It mediates the transition period by handling forwarding responsibilities temporarily, ensuring continuous traffic flow while the network converges to the new topology, thereby resolving the contradiction between preventing loops and enabling rapid convergence.
2Ease of operation
If STP convergence and TRILL convergence are executed sequentially, then ease of operation is improved, but convergence speed deteriorates
Solution Approach 1:
The patent implements preliminary action by performing the transient AF assignment during STP convergence, before TRILL convergence completes. This overlapping execution allows both protocols to converge in parallel rather than strictly sequentially, improving convergence speed while maintaining operational simplicity through a structured two-phase process.
Solution Approach 2:
The patent introduces dynamics by allowing the convergence process to transition from a static sequential model to a dynamic overlapping model. The transient AF mechanism enables the system to adaptively handle the transition period, allowing TRILL convergence to begin before STP fully converges, thereby accelerating overall convergence while maintaining control through defined phases.
Data Source
AI summary
Methods and apparatuses for rapid TRILL convergence are disclosed herein. The methods can be implemented in a network including a plurality of RBridges or in a cloud network environment including a plurality of cloud switch domains. An example method for rapid TRILL convergence can include: Executing a spanning tree protocol (STP) for network topology in a network; and executing a Hello protocol for control and forwarding at the RBridge. The Hello protocol can be configured to elect a designated RBridge and assign an appointed forwarder. The method can also include assigning a transient appointed forwarder during a period of time between convergence of the STP and convergence of the Hello protocol. The transient appointed forwarder can be configured to forward frames in the network during the period of time between convergence of the STP and convergence of the Hello protocol.