In my previous blog, I looked at some of the controversy surrounding a report entitled “802.11n: The End of Ethernet?” There is no doubt that wireless is already having an impact on Ethernet. Is 802.11n any more special?
According to the press release for the report, 802.11n is “an appropriate LAN access substitute for wired Ethernet” when:
- The number of laptop users is growing
- The enterprise uses mobile applications
- Fast Ethernet (100 Mbps) throughput is good enough
- The enterprise deploys Voice over Internet Protocol (VoIP)
- Moves/adds/changes are frequently made
- The risk of deliberate denial of service attack is low to moderate
- Ethernet cable installation is difficult
After looking at this list, I’m thinking to myself: Which of these are existing enterprise 802.11 wireless installs failing to satisfy? It seems to boil down to the promise of a faster channel rate offered by 802.11n enabling support for a larger number of mobile and VoIP users.
Sure, Fast Ethernet is adequate for the majority of workstation and laptop users. The problem is that we’ve migrated to a dedicated 100 Mbps switch port for every user. With single channel 802.11n MIMO operation we’re looking at a raw bandwidth of 150 Mbps. In single user lab tests, a file transfer can crack 100 Mbps. Single user lab tests are not real-world.
The real problem is that if we move away from our established one-port per user switched model, we’re going back to the days of shared Ethernet, only worse. With 802.11n, not only is bandwidth contention a factor, but other issues affect performance as well:
- Slower data rates at distances farther away from the access point
- Environmental interference (not necessarily other RF sources, but physical obstructions and attenuators)
- Having to manage QoS policies to support VoIP over wireless
- Being subject to RF jamming, and so on.
In other words, many of the same issues we’ve faced with any WiFi technology to date.
Going to 300 Mbps dual channel operation will help, but has many additional issues including less spectrum to deploy multiple non-overlapping access points (a requirement to afford more coverage area as well as drop the number of users sharing channels). Utilizing the 5 GHz “a” band will certainly help with the spectrum requirements but, unfortunately, reduces distances. And how about laptop support for 5 GHz dual channel’s additional power requirements, the more complex antenna systems, complete interoperability at the high end, etc.? The jury is still out.
There is no question that wireless will continue to impact Ethernet by way of eroding the Ethernet component market which appears to be the crux of the report. The title was merely a grabber. The real answer is much more complex. For instance, how do laptops really come into play? What happened to the prediction from a couple of years ago that laptops would replace desktops? But I digress.
Are we ready to go back to shared Ethernet?