Spanning Tree Protocol Adaptation in Core Networks
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Solution Overview
Problem
In networks with high redundancy or guaranteed service levels, the execution of the spanning tree protocol (STP) is not necessary, leading to scalability issues and increased overhead, particularly in large networks like Metro Ethernet and Virtual Private LAN Services, where the protocol's communication and instability become problematic.
Innovation Solution
The spanning tree protocol is adapted by disabling its execution in core networks, using a 'phantom' root bridge identifier to maintain loop-free topology without actual network forwarding nodes, reducing communication overhead and message transmission, especially in MPLS and VPLS networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spanning tree protocol is executed in core networks, then loop-free topology is maintained, but communication overhead and message transmission increase significantly
Solution Approach 1:
The network is segmented into core networks and access networks. STP is executed only in access networks where loop prevention is necessary, while core networks operate without STP. This segmentation allows the system to maintain reliability where needed while reducing overall communication overhead and complexity in the core.
Solution Approach 2:
Different parts of the network are assigned different quality characteristics. Core networks are designed with inherent loop-free topology and guaranteed service levels, making STP unnecessary. Access networks maintain traditional bridged topology requiring STP for loop prevention. This local differentiation optimizes each segment's operation.
2Reliability
If spanning tree protocol is executed in large networks, then network topology is determined, but scalability issues and instability occur
Solution Approach 1:
The network is divided into scalable access networks and stable core networks. By limiting STP execution to access networks with smaller scales, the system maintains stability while enabling core networks to scale without the overhead and instability associated with protocol execution across the entire large network.
Solution Approach 2:
The core network acts as an intermediary between access networks, providing a stable backbone that does not participate in STP. This intermediary approach allows access networks to maintain their own topology independently, improving overall network scalability and stability.
3Reliability
If spanning tree protocol is executed to ensure service levels, then reliability is improved, but overhead increases making it unnecessary in high-redundancy networks
Solution Approach 1:
Service level guarantees are implemented locally in core networks through inherent redundancy and reliable transport mechanisms, eliminating the need for STP overhead. Access networks continue to use STP where service level guarantees require loop prevention. This local quality differentiation optimizes energy efficiency while maintaining reliability.
Solution Approach 2:
The high redundancy in core networks, which would normally create loops requiring STP, is converted into a benefit by designing the core specifically to leverage this redundancy for guaranteed service levels through alternative means, thereby eliminating the harmful overhead of STP execution.
Data Source
AI summary
It is realized that the use of a spanning tree protocol in particular portions of a network may not necessarily be desired due to performance and stability reasons. A method and system is provided for executing a revised spanning tree algorithm that performs more optimally in particular network topologies. In one aspect, a spanning tree protocol is executed over a first and second network connected by a third network, wherein the spanning tree network is disabled in the third network. The third network may be, for example, a core network through which first and second Layer 2 networks are bridged. The first and second networks may be coupled by another network or network connection, and it may be preferable to allow the operation of the spanning tree network between the first and second coupled networks for the purpose of fail over to redundant paths. In network forwarding devices positioned at edges of the core network, the operation of the STP over interfaces where network tunnels of each network forwarding device attached to the core network may be inhibitied (e.g., turned off). A phantom root bridge may be created that does not correspond to an actual network forwarding node, and this phantom root bridge may have a bridge identifier which is used by network forwarding nodes as the root bridge. In this manner, STP protocols may work as intended in peripheral networks, while STP does not need to be executed in the core.