Although cloud computing solutions have been around for a while, the IT world is currently on the precipice of a monumental shift where enterprises large and small are realizing the benefits of virtualized technologies and redesigning their data centers to incorporate at least some form of cloud computing.
The introduction of cloud computing has a profound impact on a number of data center pieces, particularly the Local Area Network (LAN), which is being forced to evolve alongside the cloud. This topic, along with many other cloud-related issues, was explored in depth in a recent Alcatel-Lucent (News 
- Alert) (ALU) white paper, The 2011 Cloud Networking Report.
The Evolution of the Data Center LAN
Alcatel-Lucent found that nearly 73 percent of enterprises have either already begun the process of redesigning their data center LAN to support cloud computing or will do so in the next year. The key factor for most organizations in redesigning their data center LANs was preparations for the deployment of virtual servers.
The ALU researchers then asked respondents what percentage of data center servers that have either already been virtualized or will be within the next year, and compared those numbers to an earlier 2010 survey. The results underscore the enormous shift toward cloud computing:
- In early 2010, 20 percent of organizations had virtualized the majority of their servers
- Within the next year, that number will climb to 40 percent
- More striking, 30 percent of enterprise hadn't virtualized any servers in 2010, compared to just 15 percent now
Redesigning a data center LAN provides a number of benefits, including storage, energy reduction and data management. However, the two main benefits pointed to again and again by respondents were cost and scalability.
That said, redesigning a data center LAN comes with a number of challenges as well. These barriers include limited VM-to-VM traffic visibility, inconsistent network policy enforcement and layer 2 network support for VM migration, among others.
Third-Generation LAN Technologies
Clearly, the data center LAN is changing rapidly, and new technologies are needed to keep up. Many of these are still under development but they will be here soon, and they will be based on one thing and one thing only, Ethernet.
One change being discussed in the industry is to flatten the network from three tiers to two, consisting only of access and aggregation/core layer switches. Many believe that this will reduce latency, improve reliability and minimize the number of hops between servers. In fact, more than half of survey respondents anticipate that the number of layers in their data center will be two or fewer in the near future. However, it should be noted that two tier networks require more sophistication than three tier approaches, including switches that have high densities of high speed ports and greater levels of reliability and availability.
Other third-generation data center LAN developments that are currently being discussed include a reduced role of blade servers to eliminate switch tier proliferation and the evolving role of the hypervisor vSwitch as a port aggregator for EVB.
Addressing the spanning tree protocol (STP) challenge
Another key development is overcoming issues related to the spanning tree protocol (STP). IT organizations are looking to replace STP because it allows for only a single active path between two network nodes. This artificially limits the throughput of the LAN.
Ideas being discussed to replace STP include doing so via switch virtualization, multi-chassis Link Aggregation Group (LAG) technologies and new protocols like TRILL, which can eliminate loops and allow active-active traffic flows. The Internet Engineering Task Force (IETF) is currently working on TRILL and has put it on the standards track. And, shortest path bridging (SPB) is another alternative that is being discussed by the IEEE (News - Alert) 802.1aq working group and is expected to become ratified at some point in 2012.
OpenFlow, an open API protocol used between a network controller and a controlled physical switch, is also expected to make in impact in the LAN switch market in the next three years. The technology will allow switches from different vendors to be used at the same time without needing to worry about a negative impact on the network operating system (NOS). OpenFlow-enabled switches are currently in the prototype stage.
ALU speculates that IT managers may soon be relying on different approaches to automating data center configurations, such as provisioning and migrating VMs based on an orchestration engine. This new approach may help overcome current automation challenges like ensuring that the VM's network configuration state is established and transferred in a timely fashion.
Check out part two of the white paper, subtitled "The Emerging Data Center LAN," for details on other third-generation data center LAN technologies. These include 40 GbE and 100 GbE uplinks and core switches, new approaches to fabric unification and maturing management tools.
Beecher Tuttle is a TMCnet contributor. He has extensive experience writing and editing for print publications and online news websites. He has specialized in a variety of industries, including health care technology, politics and education. To read more of his articles, please visit his columnist page.
Edited by Peter Bernstein
