Author | Dave Cartwright Translator | Wang Qiang Reviewer | Luo Yanshan
IEEE 802.11ax-2021 (commonly known as IEEE 802.11ax, or the more familiar “Wi-Fi 6”) was approved on February 9, 2021, with a maximum speed of 1.2 Gbit/s per stream (where “stream” can be considered as a “channel”). It seems that every time a new generation of Wi-Fi technology is released, people ask the same question: will the new standard finally allow us to completely break free from the constraints of cables and fully transition to wireless connections?
However, I want to ask a slightly different question: will our world completely eliminate wired connections in the future?
First, we need not discuss the topic of wireless server rooms and data centers: that scenario will never happen. In conventional server rooms or data centers where physical servers are deployed, each device has at least one pair of Gigabit Ethernet connections redundantly connected to the switch infrastructure. Gigabit Ethernet is full-duplex (strictly speaking, the original specification also included half-duplex protocols, but they never really became popular), so as long as the devices on both ends of the communication can keep up, you can almost continuously achieve Gigabit transmission capability (I say “almost” only because you must reserve Ethernet frame bits for some non-data payloads, such as headers).
In a virtualized world, your servers run virtually on a hypervisor like Hyper-V or ESXi, and the common network option is 10 Gigabit Ethernet—also paired connections to enhance resilience.
The key point is that using wired networks in server rooms or data centers is actually quite cost-effective. Regardless of the technology you are running, there will always be some Layer 2/3 hardware in the core and (if applicable) access layer to properly handle traffic. In server environments, cabling requirements are at most within the rack, and at the furthest, a few copper or fiber cables between adjacent racks. Cabling in your office can be expensive (we will discuss this topic later), but cabling for data centers is different.
Therefore, considering that today’s Wi-Fi technology is just approaching speeds of 10 Gbit/s (using multi-stream parallel expansion), while some wired network technologies connecting to servers have bandwidth that is 40 times higher, it is hard to imagine that future wireless technologies will have a chance to catch up with wired networks in this regard. Later, we will summarize the reasons why wired connections have always dominated in server rooms.
1In Office Applications
As mentioned earlier, the main motivation for transitioning to wireless networks is cost. For several years, I have deployed LAN networks from scratch for many new office locations, but I remember the last time I did structured cabling for a not-so-large single-story office, the cost far exceeded £100,000. The complexity involved should not be overlooked: connecting floor network ports to PCs, connecting structured cabling outlets in communication rooms to switches, and ensuring that any changes that occur over time are properly documented—all of these tasks require considerable time and effort.
It should also be noted that in certain scenarios, Wi-Fi is easy to deploy. The UK Network Industry Awards have been held for several years since the mid-1990s, and I clearly remember one time when an IT service provider (now defunct) won the “Project of the Year” award for facing the challenge of deploying an enterprise network in its listed building headquarters. Their solution was primarily based on Wi-Fi, and the company was satisfied with the results. You occasionally hear such stories, which do plant the seed of “maybe this is feasible” in people’s minds.
On the other hand, wired networks: with such high costs, what real advantages do they bring? Yes, the benefit of Ethernet is the guarantee of stable bandwidth: when your laptop boots up its Gigabit Ethernet port, it has a full-duplex path in and out of the switch and can freely transfer data. In contrast, when there are walls, doors, steel structural supports, or frankly, anything solid blocking the path between a user’s PC and the wireless access point (AP), the efficiency of Wi-Fi is affected. No amount of clever design can allow Wi-Fi traffic to flow smoothly through solid objects.
Finally, Wi-Fi is, and has always been, a half-duplex broadcast technology, where communication endpoints must observe and wait for a clear window before transmitting, unlike full-duplex networks that can send data at will.
2Not a Switch
Many people question the latter point, believing that 802.11ax is essentially a switch. While this assertion is indeed based on some truth, it is not entirely accurate. Tom Hollingsworth (nicknamed the Network Nerd) pointed out in a blog post about two years ago titled “802.11ax is Not a Wireless Switch” that no matter how many patch techniques are used, Wi-Fi is still not a complete duplex network. As Hollingsworth stated: “The point is that this transmission medium has not magically turned into a full-duplex network. Access points may use some tricks to address this issue, but they still need to wait for a data idle window to send data. Remember, all stations and APs can still hear all transmissions. It is essentially still a broadcast medium.”
Does this mean that Wi-Fi can never become a switch and will never operate at stable full-duplex speeds? Indeed, theoretically, one might think that full-duplex transmission should be feasible: one can imagine a dedicated radio channel between an AP and a user endpoint—one for sending and one for receiving. But here lies the problem.
First, we must distinguish between things that move and things that do not move. The main benefit of Wi-Fi is that we can roam around the building with our phones and tablets, staying online while moving from our desks to meeting rooms. Behind this experience, communication endpoints and APs seamlessly negotiate to find the most suitable AP to provide the best experience. The idea of dedicated channels does not work in this case; you ultimately face a hybrid situation where some of your mobile devices can only negotiate wireless connections using the traditional model.
Next is the attenuation issue: Wi-Fi can only achieve its maximum rated speed when the distance is relatively short and (as we mentioned earlier) there is nothing to absorb the signal between the source and destination. But cables passing through walls do not have this problem.
The third issue is interference: we have all seen videos of microwaves interfering with 2.4GHz Wi-Fi networks. In fact, electromagnetic (EM) interference can affect wireless networks at any frequency, such as companies boosting the radio signal strength of their APs to 11, causing radio waves to spill out of your windows and interfere with signal transmission in other spaces. Fiber-based LAN networks are not affected by ordinary EM interference in typical office environments, but even copper wiring can handle interference quite well.
A few years ago, I spent my craziest day at the EM testing lab of ITT Cannon in southern England, and I was surprised to see that even unshielded twisted pair (UTP) had good resistance to EM interference. Tests on FTP cables (metal foil shielded twisted pair, UTP wrapped in metal foil) showed that they were completely unaffected by any EM bombardment we conducted. (By the way, I also learned that the walkie-talkies used by company security personnel have much stronger interference capabilities than mobile phones.)
3Limited Channel Count
So does Wi-Fi have a chance of victory? The key here is that Wi-Fi operates within a limited frequency range, and the number of available streams (channels) is always limited. Once this limit is reached, devices must start sharing channels—so the only choice for designers is to make the streams narrower and narrower, continuously reducing the error level to prevent channels from stepping on each other. But streams cannot be infinitely narrowed. In this sense, wired networks do not have limitations—they are only limited by the number of bits in the wires or fibers you use.
Wi-Fi will continue to evolve. Indeed, when people walk around buildings, taking laptops from (connected via Ethernet) desks to meeting rooms, Wi-Fi is the perfect tool. But Wi-Fi can never achieve the same speed and stability as wired networks. Yes, the cost of wired cabling is very high, but because you rarely need to re-cable, if you can reasonably spread the costs, its total lifetime budget is entirely acceptable.
Therefore, we will continue to connect to wired networks behind our desks and use Wi-Fi when convenience is needed. When we connect our laptops to wired LANs, we can leave the (increasingly faster) wireless bandwidth for devices that need mobility more.
Original Link:
https://www.theregister.com/2021/07/14/will_i_ever_ditch_my_cabled_lan
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