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Gigabit Ethernet speeds: What's the impact of 2.5 and 5 GbE?

Gigabit Ethernet speeds mean enterprises can boost wireless performance without actually replacing wiring. But there are still some considerations sys admins must make

Now that a number of Ethernet switches supporting per-port Gigabit Ethernet speeds 2.5 and 5 Gbps are on the market, and the corresponding IEEE 802.3bz standard is approved, it's time to examine what impact this very interesting technological advance might have on the networking market -- both wired and wireless.

802.11ac Wave 2 wireless LANs (WLANs) -- capable of gigabit-plus speeds -- are the primary reason enterprise buyers are investigating 2.5 and 5 GbE switches. Indeed, WLAN products today already can easily exceed the 1 Gbps per-port speeds available on Ethernet switches most commonly deployed at the network's wired edge. Before the release of the 802.3bz standard, 10 Gbps would have been the next performance benchmark, but that would have required the use of Cat 6 cable. Buildings wired with legacy Cat 5e cable, therefore, would have been unable to take full advantage of 10 Gbps performance. Swapping out 1 GbE switches to 10 GbE devices, meantime, would have been a very expensive undertaking.

This is why 2.5 and 5 GbE switches are so interesting. They provision performance that matches the capabilities of today's 802.11ac access points (APs), but over Cat 5e cabling. This means that companies don't have to replace their wiring to realize a meaningful boost in wireless performance.

New switches, new considerations

As is often the case, system administrators must face a new set of considerations, including the following:

  • While new cabling may not be required in the case of 2.5 and 5 GbE, new switches obviously are. So IT managers need to evaluate price and performance and determine the net benefits of adding or replacing existing switches. Key here is the useful life of 2.5 and 5 GbE switches: Will 10 GbE switches eventually be required regardless? Read on.
  • Avoiding the need to upgrade wiring is tempting, but there's more to think about here. All newly installed cabling will be at least Cat 6 today, but it might in fact be easier than many assume to replace existing cabling with Cat 6. What's more, 10 Gbps will often work quite well over Cat 5e cabling at shorter distances. At the Farpoint Group, our experience has shown that this can be up to 50 meters, and given that APs are often densely deployed, this option should be acceptable in many cases even if the full-rated performance cannot be achieved. But it's clearly worth a try before spending any more money.
  • The cost of 10 GbE switches is another consideration, but the appropriate question here is how quickly will per-port prices decline? We believe that 10 GbE pricing will fall quite rapidly and that 10 Gbps performance will ultimately be required. But entry costs are still a factor today, and IT shops need to carefully analyze the per-port price of 2.5/5 GbE switches versus their 10 GbE counterparts. The difference might already be manageable, if not negligible, in at least a few cases. Many current 2.5/5 GbE switches also (wisely, we might add) support 10 Gbps as well. That's an option to keep in mind if you want a little futureproofing now.
  • Which brings us to what might be the most important consideration of all: addressing the next generation of WLANs, including 802.11ad, 802.11ax and .11ay. 802.11ad can already reach close to 7 Gbps, and .11ax, now under development at the IEEE and due around 2018, is aiming at the magic 10 Gbps over-the-air number. 802.11ac Wave 2, now well-established as the predominant choice for new purchases, should be fine with 5 Gbps links. But be aware that 802.11ac is specified up to 6.7 Gbps. Keep in mind, it's unlikely many mobile devices will be able to accommodate those speeds, which require the use of eight multiple-input, multiple-output (MIMO) streams. Still, APs that are multi-user MIMO compatible may become more common. At the same time, there already has been development work toward an 802.11ax chipset capable of reaching 10 Gbps. It's likely that Wi-Fi products eclipsing 5 Gbps will become more common, and more rapidly, than many assume. (We even have a consumer-grade $350 AP specced at 5.3 Gbps currently being tested and evaluated in our lab.)

Quite a dilemma, indeed. It's clear that all IT shops will, at some point, have to upgrade their installed base of Ethernet switches to get the most out of their future WLANs. And even installing 2.5 and 5 GbE switches -- to exploit existing wiring -- could be asking for trouble if that means kicking off another upgrade cycle within two to three years' time. 

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This was last published in December 2016

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