Networking: Switching to a New Design for Intelligent LAN

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Networking: Switching to a New Design for Intelligent LAN
By Jim Metzler

August 1, 2008 —

My last few columns have focused on wide area networking. One reason is that, for more than a decade, LAN design has not changed much. Since the late 1990s, LAN design has been focused on providing high-speed connectivity and very little else. Another reason for that focus on the WAN is that IT organizations tend to spend more on their WAN than they do on their LAN. That follows because the majority of LAN costs occur only once; when the LAN switches, wireless access points and wiring are installed.

In contrast, WAN costs recur monthly, and the cost of WAN connectivity increases somewhat linearly as the size of the bandwidth increases. For example, a common WAN circuit is referred to as a T1 link. A T1 link runs at 1.544 Mb/sec. If a company has a T1 link at one of its branch offices, and if it outgrows the capacity of that link and decides to add a second T1, their monthly WAN costs will double.

Given the cost of WAN circuits, when network engineers design their company’s WAN, they typically place a heavy emphasis on minimizing cost. The last few years, however, have also seen the deployment of WAN designs that incorporate additional intelligence into the WAN. For example, a number of IT organizations have deployed network optimization solutions that are designed to both reduce the cost of the WAN and to make it perform better. Future columns will discuss these solutions in detail.

In contrast to the WAN, LAN design has historically been about two things: availability and performance. However, as I mentioned in my first column, we are possibly at an inflection point relative to LAN design. In particular, many vendors are now making the claim that, similar to what has been happening in the WAN, that more intelligence must be added to the LAN to support new demands such as enhanced security.

At the Interop conference held in Las Vegas in April, I moderated a session that touched on the need to add intelligence to the LAN. That session was titled “Implementing Policy and Control,” and it looked at the need to implement control functions in the IT infrastructure to both improve application performance and to provide enhanced security.

One of the most compelling arguments for a new approach to LAN design is that, as a result of the current approach to LAN design, even the most basic levels of IT control can be cumbersome. For example, IT must rely on virtual LANs and access control lists (ACL) to segment user traffic and protect resources. Implementing and maintaining VLANs and ACLs is time-consuming and prone to error.

In addition, legacy switches make it difficult to enable new services such as VoIP, requiring IT to build a separate VLAN for VoIP traffic and to define quality of service policies manually. Deploying wireless connectivity typically means building another parallel infrastructure that requires separate access controls, further increasing both network complexity and the operational burden on IT.

Troubleshooting user and application problems is complicated in the current LAN environment by these service overlays as well as by the inability of legacy LAN switches to correlate user and application information. For example, today if a user calls into IT with a problem, IT has limited visibility into that specific problem. Additionally, a lot of manual effort is required to identify the source of the problem.

The current approach to troubleshooting problems lengthens the mean time to repair and it also consumes key IT resources. To put this into perspective, the typical IT organization spends 75 percent of its resources on supporting ongoing operations, and this percentage has been growing over time as the IT infrastructure has become increasingly complex. Unfortunately, this ongoing operational burden leaves the IT organization with a relatively small and diminishing set of resources with which to drive new initiatives.

Driven in part by the desire to reduce the operational burden of supporting LANs, a handful of LAN switch vendors have begun to deploy a new generation of intelligent LAN switches, in which information about users, devices, roles, applications, flow and destinations is native to the switch. The goal is to simplify user and application control by managing it directly through the infrastructure.

From a physical perspective, one of the biggest differences between legacy LAN switches and the emerging generation of intelligent LAN switches is that legacy switches are built around merchant silicon and fixed Application Specific Integrated Circuits optimized for fast forwarding at Layer 2 and Layer 3. In contrast, intelligent switches also include programmable processors that allow the hardware to support a rich set of services that can be updated and expanded over time. Another key difference is that legacy switches operate on packets, whereas intelligent switches process traffic based on flows, enabling them to correlate user, application, destination and other information.

Granular control is just one reason IT organizations are beginning to deploy a new generation of intelligent LAN switches. I have created a session for the Interop conference that will be held in New York City in September titled, “Do Applications Require a Next-Generation LAN Design?” If you are attending the conference, I hope you will attend that or any of the other 10 sessions I am moderating there.

In any case, I will summarize that session in a future column.

Jim Metzler has worked in just about every aspect of the networking industry in more than 30 years of professional experience. He can be reached at jim@ashtonmetzler.com.

Related Search Term(s): networking, testing & troubleshooting

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