Personally, I'm not too worried about it.
While naively adding up the wireless marketing sheets gets you to > 1Gb
numbers, especially when treated with Wave 2 pixie dust, I think there are a
few factors which make this a low concern.
- The wireless numbers are half duplex, while that 1Gb wired connection is
full duplex. This means that while your client bandwidth is probably going to
be biased download more than upload, the upload and download packets that are
bottlenecked through the common air time each have their own contention-free
1Gb channel once they hit the wired network.
- Wireless throughput is *very* picky at top speeds. I've seen estimates
that those magic wave 2 numbers won't be reachable more than a few meters away
from the AP.
- It only takes a few legacy clients hopping onto your nice new 11ac AP to
drag you back down to a fraction of your peak throughput. Given how many
budget laptops are being sold today with 2 stream, 2.4GHz only 11n adapters,
this problem will be with us for a long time.
Even if you do end up in a situation that legitimately needs over 1Gb, I'd be
careful before relying on the LACP based solutions. Unless you're terminating
your user sessions locally, all of the traffic will be going through an
encapsulated tunnel between the AP and controller, which can easily end up
hashing all of the traffic down one link. There are tricks to work around
this (I believe Aruba opens up multiple tunnels with different endpoint IP
addresses, for example), but this it's still an imperfect solution where 1 + 1
!= 2.
So my guess is that we have a few years before it's a major concern, and I'm
waiting on a decent answer for 2.5Gb switching before I do any real investment
in a solution.
Frank Sweetser fs at wpi.edu | For every problem, there is a solution that
Manager of Network Operations | is simple, elegant, and wrong.
Worcester Polytechnic Institute | - HL Mencken
On 3/24/2015 10:37 AM, Hinson, Matthew P wrote:
I’ve seen a few articles here and there regarding possible solutions for “the
gigabit bottleneck” as it pertains to .11ac access points. Said solutions
include Cisco’s forthcoming protocols for 2.5G and 5G over CAT5 cabling as
well as LACP’ing two gigabit ports per switch and AP as some vendors suggest...
My question for the group is: Has anyone actually seen a throughput issue
using gigabit to the edge? Certainly your distribution layer gear could be a
limitation if it’s not specced correctly, but I’ve just never seen a situation
where I’ve wished for more than 1000BASE-T to an AP. Our fastest 802.11ac
access points can “only” hit 600-700mbit/s real TCP throughput, and that’s in
ideal, almost laboratory conditions.
Thoughts?
Thank you!
Matthew Hinson
Network Operations
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