Data centers have seen a lot of change in the last five years, moving from static configurations built from physical components to a virtual infrastructure that abstracts the environment and allows for mobility. On July 27th, 2010, the Wikibon community welcomed Brad Hedlund, Technology Solutions Architect from Cisco Systems, to discuss how these changes are impacting data center networking. Data Centers today require high performance, highly scalable designs. The options available to re-architect networks have grown dramatically in the last 3 years.
Spanning Tree Replacements
Spanning Tree Protocol (STP) is a link layer network protocol that allows only a single link to be active between any two nodes. This helps ensure a loop-free topology but limits the total bandwidth of the network. Switch architectures were designed with limited bandwidth to support these over-subscribed configurations. Spanning Tree has been enhanced in ways over the years – see details in Wikipedia.
In 2007, Cisco started offering solutions that took the place of Spanning Tree, first with Virtual Switching System (VSS) for the Catalyst switch line and then Virtual Port Channels (vPC) for the Nexus switch line in 2008. VSS and vPC both make a pair of switches look like a single logical switch. These technologies require new hardware, software, and architectural changes, plus network downtime, to deploy. They are becoming popular for new data center architectures but are a challenge to implement in existing environments, requiring CIOs to find a compelling business value to justify the cost and production downtime to deploy.
Cisco recently announced a solution called FabricPath, which is a “superset” of the IETF proposal TRILL (Transparent Interconnection of Lots of Links), providing an option to replace STP and provide greater scalability and flexibility than VSS and vPC. This will typically be for environments that require thousands of ports. Many use cases for TRILL and FabricPath will be on FCoE environments (where SAN configurations use multi-path configurations) and HPC configurations, which require non-blocking, high performance, and scalability.
As environments migrate from 1Gb to 10Gb Ethernet and eventually to 40Gb and 100Gb, the cost of ports becomes more expensive, dictating full utilization of assets, which can not be accomplished with traditional STP and will drive the adoption of replacements such as VSS, vPC and TRILL/FabricPath.
Action Item: Internal IT infrastructure must increase their own efficiencies in the face of growing competition from cloud offerings. CIOs should pilot the new network technologies discussed to determine the impact of new architectures on their stack and on change control and management practices. Look for solutions that support interoperability and commitment for standards support.
Footnotes: Post from Brad Hedlund on TRILL