Network Allies Blog What are the Advantages of Full Mesh Fabric aTCA?

Migrating from a dual-star topology to a full-mesh topology can produce a dramatic increase in bandwidth in AdvancedTCA systems, as well as simultaneous increases in processing power and reliability. While there may be issues involving compatibility and software complexity in this type of migration, the benefits far outweigh any possible downside.Let's take a look at a hypothetical case with a 16 slot chassis using 10GigE as the fabric interface. The dual-star 16-slot system consists of 16 identical node cards. A dramatic increase in bandwidth can be achieved when migrating to a full-mesh system, whether we are talking about internal or external system bandwidth. We'll compare with each of these hypothetical cases.Bandwidth Comparison in an Internal SystemInternal system bandwidth is the total amount of bandwidth available for nodes to communicate with each other, excluding any bandwidth used by nodes to communicate with components outside of the AdvancedTCA chassis. In the case of a dual-star topology, a 16 slot system would have 580 Gbps of total internal bandwidth. Using a full-mesh system, there would be 2720 Gbps of bandwidth, or 4.7 times more than the dual-star approach.Bandwidth Comparison in an External SystemExternal system bandwidth is the total amount of bandwidth available for nodes to communicate with components outside of the AdvancedTCA chassis. Whether the primary external connection is on the switch cards or on the node cards, the full-mesh topology offers an increase in bandwidth. In the case of systems with the primary connection on the switch card, there is a dramatic increase in bandwidth, since any card can be used for an external connection.Improved Failover and RedundancyIn addition to providing a dramatic increase in bandwidth, a full-mesh topology also offers improved failover and redundancy. Since each node can communicate directly with any other node, any two functioning nodes in the system can continue system operation in the event of the failure of any other node cards. Increased Processing Capacity A full-mesh system can provide increased processing capacity, because all 16 slots in the system can be node cards, whereas in a dual-star system, two of the slots in the chassis are assigned for exclusive use a fabric switch slots. This yields a 14% increase in the number of node cards per chassis. There is also a significant cost savings, because you don't have to purchase dedicated switch cards in a full-mesh system.Concerns about compatibilitySince the dual-star backplane routing is a proper subset of the full-mesh backplane routing, compatibility issues are easily mitigated in AdvancedTCA® systems. This means that full-mesh and dual-star cards can be used together in both full-mesh and dual-star system configurations.ConclusionFull-mesh and dual-star are not the only choices for system configuration in AdvancedTCA® systems, but they are the most common choices. Any penalty for full-mesh architectures in system configuration complexity and possible software complexity will be offset by the dramatic increase in bandwidth, processing power, and reliability of the full-mesh system over dual-star systems.