One of the primary ways to increase data center efficiency is to simplify the infrastructure. Most data center network infrastructures in place today deploy a three- or four-tier architecture. A simplified two-tier design, made possible by taking advantage of the enhanced performance capabilities of today’s Ethernet switches, will reduce cost; complexity and increase efficiency without compromising performance.

During the 1990s, Ethernet switches became the basic building block of enterprise campus network design. Networks were typically built in a three-tier hierarchical tree structure to compensate for switch performance limitations. Each tier performed a different function to distribute the workload. The access layer connected servers or users. The aggregation layer was used to aggregate access layer switches. Services, such as Access Control Lists, were typically provisioned at this layer. The main function of the core layer was to interconnect the aggregation layer switches and perform switching with a minimum of features provisioned. When Ethernet moved into the data center displacing SNA, DECnet and token ring, the same topology was deployed.

Factors Influencing a Change in DC Infrastructure Design

The three-tier architecture worked well in a client-server world where the traffic was primarily north and south with lower traffic flows. However, today’s data center network is more complex. New technologies drive growth and complexity. Also, inter-process communications (IPC) were within the server itself. However due to the explosion of the Internet, applications have increasingly moved from client/server to a service-oriented architecture (SOA). Thus, processes that were on the same server are now distributed across multiple servers interconnected by the network itself with traffic flows now running mostly among servers or “east-west”. A three-tier architecture is less efficient since for traffic to travel east-west, among servers, it must first travel north-south across the multi-tier hierarchy increasing latency.

In the future, the added latency and buffering of a multi-tier network may not provide the low latency loss-less behavior required by storage protocols. This will apply to companies that are considering converging storage traffic from an existing dedicated Storage Area Network (SAN) onto their Ethernet infrastructure.

There has also been an exponential increase in the number of devices and users that need to be connected: servers, storage, mobile/remote users and business partners, all of which drive an increase in traffic and higher performance requirements for the infrastructure. Scaling a multi-tier architecture to meet these requirements can add more complexity.

Increase Infrastructure Efficiency with a Two-Tier Design

Building networks for traffic patterns that are five to ten years old and based on performance assumptions of early generation switch architectures is not optimal. The results can be lower efficiency in terms of physical space, power and easily scalable performance.

Ethernet switch capacity has grown dramatically. With advanced functionality now performed in hardware rather than software, today’s Ethernet switches can deliver line rate performance, with complex services enabled, scaling to terabit performance. As a result, high performance, scalable networks can now be designed with only two tiers, which connect the access layer into a single collapsed aggregation/core layer. There is also technology available to virtualize access layer switches used for top-of-rack server connectivity and more efficiently process today’s “east-west” server to server traffic directly at the access layer. A two-tier network design leveraging the increased performance capabilities of today’s Ethernet switches will, in most cases, meet the performance/latency and scalability requirements of today’s data center.

This simplified design will inherently have lower space and energy requirements, resulting in a more efficient data center infrastructure while meeting the performance/latency and scalability requirements demanded by today’s users and business applications.

John Bartlomiejczyk is Senior Manager, Enterprise Field Marketing: Data Center Solutions at Juniper Networks, 408-936-4015; email: jbartlom@juniper.net; web: www.juniper.net.