802.11n Drives an Architectural Evolution

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802.11n Drives an Architectural Evolution
Introduction Today's enterprises deploy wireless LANs (WLANs) as a standard business tool to drive productivity and enhance collaboration. Enter the state-of-the-art WLAN-802.11n. Organizations can expand their wireless capabilities with this expanding technology to dramatically boost network capacity and speed-up to 600 Mbps (see Figure 1). There are major implications as to how organizations will use and implement wireless networks moving forward. Contrast this with the 54 Mbps of 802.11a/g networks or the 100 Mbps Fast Ethernet. This extra capacity and speed will allow organizations upgrading to 802.11n to expand the range of applications mobilized over wireless networks, including both existing and ground-breaking high-bandwidth applications, which may help to streamline business processes and foster corporate competitive advantage. Figure 1: 802.11n brings a dramatic increase in traffic
Contents at a glance Introduction 1 Legacy WLAN 2 architecture: centralized WLAN switch The 802.11n-ready 4 network: optimized WLAN architecture Conclusion: WLAN 6 architectural changes are a natural evolution HP ProCurve mobility 6

Whether or not an organization wishes to deploy 802.11n in the near term, an architecture that can be quickly adapted to facilitate technological advances is a major consideration when making a WLAN investment decision. The sharp capacity increase possible with 802.11n is a compelling force behind the evolution in WLAN architectures, and every organization must examine the impact this exciting new technology will have on WLAN scalability, LAN performance, and IT budgets of the future. Increases in throughput with 802.11n will also have a major impact on a traditional, centralized WLAN switch architecture. However, an enterprise-grade alternative is available-the optimized WLAN architecture. This expanding solution is specifically designed for 802.11n environments, helping to ensure a cost-effective migration while providing high network performance, scalability, and easy management. This paper examines both the centralized WLAN switch architecture and the optimized WLAN architecture, so that the wireless network choice an organization makes today will protect its investment and allow it to experience the substantial benefits of 802.11n for years to come. Legacy WLAN architecture: centralized WLAN switch Over the past 4 years, enterprises settled on a centralized WLAN switch model to deliver wireless network services. It consists of thin/light access points (APs) and a centralized WLAN switch. The WLAN switch controls all traffic forwarding decisions, and the AP simply provides wireless access (and in some cases, encryption). In this model, all wireless traffic travels from the AP to the WLAN switch, where the traffic is integrated into the wired network and forwarded to its proper destination (Figure 2). When compared to first-generation autonomous APs, the centralized WLAN switch architecture brought several benefits, including central management, security, and the ability to roam across APs. The ability to manage security, quality of service (QoS), RF configuration, and roaming from a central point, rather than managing each AP separately, greatly reduced the burden of wireless network deployment and potentially lowered the cost of ongoing operation. On the other hand, sending all wireless traffic through a centralized WLAN switch has several limitations: . Inefficient application delivery: A centralized WLAN switch architecture forces all wireless traffic to make a detour through a centralized switch before making its way to the application server, adding unnecessary latency to application response time. For real-time applications, such as voice, this indirect route may seriously degrade application quality. . Increased load on wired core: The traffic detour to the controller doubles the load on the wired infrastructure as each wireless packet is switched twice through the LAN backbone (Figure 4). This problem will be greatly magnified with 802.11n. . Performance bottleneck/Single point of failure: All wireless traffic is completely dependent on the health of the centralized WLAN switch. As wireless traffic increases, so does the load on the central switch, increasing the likelihood of performance bottlenecks.... [download for more]