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Operators make multigigabit switch push in campus networks

As applications become more bandwidth-intensive, operators are racing to install multigigabit switch foundations in their campus network architectures.

Applications and devices such as updated Wi-Fi switches, 4K streaming video and servers with 25 GbE interfaces have ratcheted up bandwidth requirements throughout the network. At the same time, a multigigabit switch topology transition is currently underway.

Network core links -- rated at 40 GbE -- are now being replaced by 50 GbE links. At the aggregation layer, 10 GbE links are being swapped out for 25 GbE connectivity. And this transition has been accelerated by the decreasing costs of 25 Gb and 50 Gb interfaces.

Servers regularly shipped to campus data centers or to serve as departmental servers are now equipped with 25 GbE interfaces. The switches connecting servers to the network must also support 25 GbE, and in the core, 25 GbE capable top-of-rack switches connect among racks using 50 GbE or 100 GbE links.

Outside the core, 25 GbE switches are being installed in the aggregation layer. They are joined to access layer switches which, in turn, connect to the devices that generate and receive data. These multigigabit switches are being upgraded to support applications and devices that generate ever higher data rates.

Devices, applications demand higher data rates

Network upgrades are fueled by a variety of factors. Among the most prominent is the ever-evolving Wi-Fi standard. Wi-Fi 5, or 802.11ac, access switches have been available for several years and are widely installed. With a theoretical maximum throughput of 1.7 Gbps, these switches dramatically boosted throughput to levels far beyond the earlier 802.11n specification. As a result, although in practice the top rate is never achieved, Wi-Fi 5 led network managers to increase -- from 10 GbE to 25 GbE -- the bandwidth needed to connect access switches to aggregation switches.

The next generation of Wi-Fi is now on deck. The 802.11ax standard, or Wi-Fi 6, should be certified next year, but early components are already available. The new spec is designed to support a theoretical maximum of four times the data rate of Wi-Fi 5. Initial installation of these switches will be in high-density locations, such as auditoriums, cafeterias, ballrooms and large conference rooms. Planning for these switches will require capacity upgrades throughout the network.

Wi-Fi 6 will usher in the use of even more bandwidth-intensive applications, such as 4K video. A single stream of 4K video will require at least 15 Mbps throughput -- and preferably 25 Mbps. 4K video will underpin activities such as digital learning, which will require schools and colleges to quickly beef up their network infrastructures.

Other factors strain network performance

IoT, meanwhile, is also evolving, with new devices and uses of the technology developed every day. Some of these devices deliver very large amounts of data. Others do not have a heavy network load but are very sensitive to delay. An increase in network capacity can decrease delay throughout the network.

Also contributing to network loads are advances in data processing techniques, such as the analysis of very large databases, which requires multiple processors and moving large data sets over the network.

Private LTE cellular service is another intriguing development. Although not widely used today, it's expected to be a valuable network technology for use in large warehouses, areas with a variety of IoT devices, or facilities with employees and equipment moving around a large area. Covering these types of areas with Wi-Fi can be difficult. LTE has greater range and devices consume less power to connect to an LTE network compared to Wi-Fi.

For mobile devices, the maximum LTE data rate is roughly 100 Mbps. Fixed devices can achieve rates approaching 1.5 Gbps. Private 5G service is not yet available but is clearly on the horizon. It will offer download rates up to 20 Gbps. Introduction of private LTE, and, later, 5G, is one more factor contributing to increased network loads.

Prices of 25 and 50 GbE switches have fallen

A key component in an Ethernet interface is a circuit that receives 64 bit units of parallel data from memory and converts it to 64 bits of serial data that is then transmitted over the network. The receiving end performs the reverse transformation. Circuit technology was limited to 10 Gbps; 40 GbE interfaces were constructed by using four 10 Gb circuits in parallel.

In 2014, work began on a 25 Gb standard and technology to support that rate. The IEEE standard for 25 GbE was finalized in 2016. Circuit technology advanced and made possible 25 Gb serializer circuits. Today, an interface with two-and-a-half times the throughput of a 10 Gb unit is available for only a slightly higher price.

Components with 50 GbE interfaces achieve greater throughput than 40 GbE and lower the price by using two 25 Gb serializer circuits. All the major network multigigabit switch vendors offer fixed configuration and modular switches supporting both 25 and 50 GbE interfaces.

Upgrades from 10 and 40 GbE links to 25 and 50 GbE are currently underway. These will continue as new applications are introduced and impose ever-increasing demands on the network. At some point, new devices and technologies -- beyond those in use today -- will fuel the next advance.

This was last published in June 2019

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