So I am guessing from this conversation that the reason the bandwidth
consumption remains the same regardless of one or multiple vlans is because
the frequency still sees the broadcast even if most vlans do not. And the
frequency is what counts. {please correct me if I am wrong}. Hence an arp
from a client uses the same amount of bandwidth regardless of the number of
total clients that see it because vlans share the same bandwidth
(frequency) with one another given any AP.
Even if bandwidth is not an issue, wouldn’t performance still remain an
issue if end devices have to process and drop/ignore higher volumes of
broadcast traffic on a regular basis?
And if one resolves that issue by blocking all broadcast traffic, does that
affect layer 2 apps like Chromecast?
Tim
*From:* The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:
WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU] *On Behalf Of *Jake Snyder
*Sent:* Tuesday, July 26, 2016 11:25 AM
*To:* WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU
*Subject:* Re: [WIRELESS-LAN] How big are your wireless segments?
Actually, they don't have to "respond." They have to process the incoming
frame. If they aren't listening for that port, they will ignore or drop
the packet.
If you are talking about client impact to CPU/battery/etc, I agree. If you
are talking about airtime, the sum of the broadcast traffic is the same.
Stopping broadcast over the air is the scalable way to solve
Thanks
Jake Snyder
Sent from my iPhone
On Jul 26, 2016, at 6:00 AM, Osborne, Bruce W (Network Services) <
bosbo...@liberty.edu <bosbo...@liberty.edu>> wrote:
Actually, you reduce the broadcast traffic with smaller subnets. Remember
that all clients on the subnet **must** respond to a broadcast.
Smaller subnets generally mean fewer clients responding to a given
broadcast. This leaves more airtime for productive Wi-Fi traffic.
*Bruce Osborne*
*Wireless Engineer*
*IT Network Services - Wireless*
*(434) 592-4229*
*LIBERTY UNIVERSITY*
*Training Champions for Christ since 1971*
*From:* Jake Snyder [mailto:jsnyde...@gmail.com <jsnyde...@gmail.com>]
*Sent:* Monday, July 25, 2016 1:28 PM
*Subject:* Re: How big are your wireless segments?
One thing to remember is that over the air you have the same amount of
broadcast whether it is one vlan or a pool of 4.
For Example: If you have 4 client segments that are a /24, and each AP has
a client on one of the 4 subnets, you still send the sum of 4x /24 network
broadcast over the air. Meaning only on lightly loaded APs where you don't
have all 4 subuets do you get a net gain of airtime. Same applies for
link-local multicast. Smaller subnets in pools don't really gain you much
without the suppression techniques, and with the suppression techniques,
you don't need the smaller subnets.
The place where pools/groups of vlans are attractive is where you may be
using public IPs and don't have a large contiguous block of IPs in which to
place clients. So picking 4 non-contiguous /24 networks is easier to do
than picking a full class B.
On Mon, Jul 25, 2016 at 11:04 AM, Tim Tyler <ty...@beloit.edu> wrote:
Brian,
We have pools of /22 /23/ and /24. We separate our pools from students
vs fac/staff (still on the same ssid). It may be ok to do /16. I know
that Aruba does a lot to prevent broadcast storms, but I feared the
overhead of one large segment might have on it. We also give students a
different ip pool depending whether they are in a residential building vs
an academic/admin building. This allows us to shape traffic differently.
But this will become less of an issue as we acquire more bandwidth
(hopefully).
I am curious of those using /16, does that resolve your layer 2
issues? Aruba does a good job of bridging many layer 2 solutions anyways,
but having one /16 vlan does seem enticing and perhaps unnecessary for
bridging protocols. However, I am curious about other overhead efficiency
issues.
Tim
*From:* The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:
WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU] *On Behalf Of *Brian Helman
*Sent:* Monday, July 25, 2016 10:22 AM
*To:* WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU
*Subject:* [WIRELESS-LAN] How big are your wireless segments?
We are in the process of moving from a controllerless vendor to Aruba. Our
current design is very segmented, to keep wireless device broadcasts from
overwhelming the network and AP’s (we had this problem back in 11g days).
Presently, we’ve limited segments to /23’s (give or take). In your
controller-based environments, how large have you let these segments go?
Is a /21, /20 … viable?
-Brian
____________________________________
*Brian Helman, M.Ed *|* Director, ITS/Networking Services | *(: *978.542.7272
<978.542.7272>*
*Salem State University, 352 Lafayette St., Salem Massachusetts 01970*
*GPS: 42.502129, -70.894779*
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