Key factors to consider before evaluating campus edge switches

As you investigate your organization's need for campus edge switches, it's important to first determine whether you're refreshing the existing switching or need to upgrade it to support new uses. Then, with this information, you can select the switch with the feature set that best meets those requirements. Wireless LAN networking is certainly an important consideration, and the rise of wireless-first networking can sometimes obscure the importance of the wired infrastructure that's still required to not just underpin your network, but to also allow it to connect to third-party networks.

The continual evolution of IoT puts another spotlight on campus edge switching, as data from devices ranging from wireless cameras to sensors can dramatically increase the amount of data these switches must process.

Before we examine switch features, a short refresher: The campus edge switch is part of a three-tiered model that anchors most campus networks. At the center is the core switch, which communicates with distribution layer devices. Edge, or access, switches provide connectivity to wired desktops as well as to wireless access points. These will generally be switches with 1 GbE (gigabit Ethernet), 2.5 GbE and 5 GbE port speeds, with a small number of 10 GbE uplinks. There are literally dozens of campus edge switches available, even as market consolidation has reduced the number of vendors selling these switches. As you evaluate your edge switch purchase, keep the following key factors in mind:

Architecture. Unless your organization is building a greenfield site, it already has some deployment architecture in place, whether it's a multipath, leaf-spine architecture or the classic core-aggregation-edge architecture. As noted above, IoT could dramatically increase your campus traffic and trigger changes in how you architect your network.

Segmentation or slicing. IoT and software-based networking are redefining network segmentation. Traditionally, networks were segmented at Layer 2 by using virtual LANs and at Layer 3 using IP subnets. Today's edge switch vendors talk about building a network within a network to separate existing traffic from the presumed deluge of IoT traffic. The mechanisms for implementing the segment or slice will vary, as does the scope of the segmentation. Some vendors will segment not only the data plane where the actual traffic transits, but the control, or management, plane as well. Regardless of the tactics used by edge switch vendors to orchestrate traffic, be aware of the edge switch's segmentation or slicing capability and determine whether it's something your organization requires for its current or near-future campus network.

Performance. Switch performance is an important factor in any purchase, and fortunately, good, basic performance is a given. Consider evaluating edge switches in terms of relative performance. For example, ask switch vendors questions like "What is the cost per gigabit per second of throughput?" or "What is the throughput per watt?" with respect to power consumption. These questions, along with the more common price-per-port metrics, will help you understand not just raw performance but what your organization is being charged for that performance.

Form factor. Generally, switch form factors are listed as fixed port or modular, which are self-explanatory terms. But fixed port typically means a mostly rather than completely fixed port. Many of these switches will have uplink slots where different topologies can be inserted. So even fixed-port switches will frequently have some element of modularity. Fixed port used to be synonymous with low end, but that's no longer the case. While low-end switches are still mainly delivered in a fixed-port configuration, so are a lot of high-end switches. So, modularity can be as basic as having modular uplinks available or, for higher density, using fully modular, chassis-based switches loaded with Gigabit Ethernet "edge" modules.

Port topologies. Port type and density are two basic considerations when picking an individual switch. For access or edge switches, there's 1, 2.5, 5 and 10 GbE, and for aggregation switches, there's 10, 25, 50, 100 and 200 GbE.

Organizations in the market for edge or access switches should focus on the 1 GbE to 10 GbE range; 1 GbE is still the typical rate for desktops, older wireless LAN (WLAN) access points (APs) and most edge networking gear, whereas 10 GbE ports will typically be used as uplinks to the aggregation layer or for server connections.

But what about 2.5 GbE and 5 GbE? Although these increments may seem odd, they exist because of IEEE 802.11ac. Now known as Wi-Fi 5, this was the first WLAN standard to push aggregate capacity through the 1 Gbps barrier. This meant that, for the first time, the 1 GbE connection between the access point and the switch was a potential bottleneck. Thus, 2.5 GbE and 5 GbE are focused almost exclusively on providing the uplink between newer Wi-Fi 5 and, soon, Wi-Fi 6 (802.11ax) APs. They also run over copper cable that's likely already in place, which provides the power to the AP.