Access Point Capacity

GoMurica
Comes here often

Access Point Capacity

Hello, 

 

I have Meraki access points deployed at many client's locations. I have a question regarding the usage of different models and the load capacity that is associated with them. At one of our locations, we have 6 MR-16s deployed. This location is a co-working location and can generally see around 100-150 people on the network on any given day. Another co-working location (about the same size and amount of people), has 6 MR-32s. This location sees more action than the previous one. Our third location is larger than the previous two locations. This location has 12 MR-42s deployed. Is it necessary to have MR-42s deployed in locations where there is a high density of people, or is adding more MR-16s enough? We want to solve the issue of capacity, not coverage. 

 

Thanks for the help in advance!

7 REPLIES 7
Uberseehandel
Kind of a big deal

Unfortunately, you haven't told us anything about how much traffic there is on your WiFi networks.

Robin St.Clair | Principal, Caithness Analytics | @uberseehandel

On any given day, there are around 100-150 on the WIRELESS network. There are more people using the wired network, but that is how many are on the Wifi


@GoMurica wrote:

On any given day, there are around 100-150 on the WIRELESS network. There are more people using the wired network, but that is how many are on the Wifi


Number of users is not helpful without an indication of data volumes.

What is the volume of data that travels over the WiFi networks, how busy are the APs, what is the average data rate, what applications are being run?

 

You have given us no information that can help produce an answer to your question. Nothing you have said allows anybody to gauge how close to maximum theoretical throughputs the WiFi networks are at your sites.

 

All the information you need to supply in the first place is available in the Dashboard for each of the access points.

Robin St.Clair | Principal, Caithness Analytics | @uberseehandel

My apologizes. Here is the requested information. For the location with the MR-32s, for the last day, 69.51 GB of data was used on the wireless side. The applications that were mainly used were Office 365, software updates, Slack, Google, Gmail, etc.. 

 

For the location with the MR-16s, for the last day, 21 GB of data was used on the wireless side. The applications that were used were the same as mentioned above. 

 

Because yesterday was the weekend, these locations were not very busy. If I look at the data over the past week, here are the results: 

 

MR-32 location: 427.89 GB 

   Applications: Misc Secure Web, UDP, email, Itunes and music, Social, Youtube

MR-16 location: 347.34 GB

   Applications: File sharing-Dropbox; Adobe, Social Web, Itunes, email, Office 365, Misc...

 

Please let me know if you need any additional information. 

 

Thanks, 

Thanks for that - you have given me something to work with - I'll get back to you (it is early evening where I am)

Robin St.Clair | Principal, Caithness Analytics | @uberseehandel

First, some back of the envelope theoretical calculations to check that you are not running into theoretical capacity limits.


Estimation of traffic (per second) - Assumptions

  • All data activity occurs over a 40-hour week
  • Data usage is evenly spread across the 6 APs
  • The available data rate of a standard AP is generally considered to be 40% of nominal throughput under benign operational conditions
  • To allow for operational overheads, a 20% network overhead is assumed, so conversions from Bytes to bits is done on an overhead adjusted basis (10-bits per Byte)


AP Capacity

  • Per AP Nominal rate 1.3 Gbps
  • Per AP Available rate 0.52 Gbps
  • 6 AP Total Capacity 3.12 Gbps


Wireless Data Usage

  • 6 APs -Aggregate per week                       430 GB
  • Average usage per second per AP              52Mbps


Explanation of units used

  • Gbps            Gigabits per second
  • GB               Gigabytes
  • Mbps           Megabits per second
  • 8 bits (b) = 1 byte (B)

Because of packet overheads inherent in the OSI model, which different manufacturers include/exclude from their explanations of how packet sizes are calculated (different CISCO products do not always calculate this the same way), and the seldom discussed overheads created by error-correction techniques, a rough rule of thumb when calculating the number of bits to transmit over a link is to multiply the bytes by 10, rather than the 8 than is the actual conversion figure.

 

The good news is that, in aggregate, you have plenty of spare capacity.

 

Unfortunately, the real world doesn’t deal in averages, users judge the adequacy or otherwise of a network by the worst-case experience.


Virtually anything to do with networks tends to have its bursty moments. At the start of the day, before and after the mid-day break, and before leaving at the end of the day, are all times when there is atendency for users to be active concurrently.


Few users watch youtube all day, but if something is going viral, peak usage may be many times greater than a few minutes earlier. And users will complain if the system can't take this in its stride.


The best handle you can get on the peaky nature of your WiFi traffic is found on the dashboard pages for the individual APs. Select an AP from the list and scroll down the detail page and you will see graphs showing live traffic on the uplink, and further down the page, usage. Both graphs show usage in bits per second. Along with the list of Access Points, these will show which of the APs has the most users, the greatest data volumes and how the various 2.4 and 5 GHz networks are configured, in terms of channel width and available capacity.


Wireless networks perform best when the hardware is not swamped by transient peaks. Particularly in the 5 GHz portion of the radio spectrum, having more APs operating at lower transmit power is preferable to fewer APs at maximum power. The devices they communicate with have much lower powered radios. For a WiFi link to be initiated and maintained both host (client device) and AP must be able to communicate with each other, it isn’t like broadcasting.

 

Because there are more non-overlapping channels available in the 5 GHz band than the 2.4 GHz band, and 5 GHz signals have roughly half the propensity to propagate as those of the (Usually over-crowded) 2.4 GHz band, we can eliminate gaps in coverage by placing additional 5 GHz APs, without diminishing overall throughput. Don’t worry about having more APs than you think you need, if properly set up, it will cause less management issues and greater user satisfaction.

 

I don’t have specific data on how many users different AP models can handle in different scenaria, it would be interesting to hear from some of the school network administrators as classes tend to do quite a lot in unison, so it gets very bursty. I did discover that half a dozen kids on a sleep over equipped with tablets and phones hoovered up the bandwidth watching videos aqnd chatting about it.


If any specific APs are getting overloaded, then there is quite a lot that can be done as far as network tuning and user management is concerned, but the hows and whys of that are for another day.

Robin St.Clair | Principal, Caithness Analytics | @uberseehandel
PhilipDAth
Kind of a big deal
Kind of a big deal

I can't answer your question directly.  It seems you are actually asking about a comparison of the AP models.

 

The current 2x2:2 access point is an MR20.

The current 3x3:3 access point is an MR42.

 

Considering only coverage, a 3x3 access point is able to better handle interference better than a 2x2 access point.  If I think I am going to have even a slightly complex WiFi environment I go with the MR42's.

 

I personally only use 2x2 access points for guest WiFi (usually when a customer needs a single AP), or when the customer generally doesn't care about the quality of the bandwidth or the performance, and just wants the coverage at a price point.

 

I personally would avoid mixing 3x3 and 2x2 access points in the same space as well.  This will make you very dependent on the quality of WiFi drivers - and there are many drivers that are not good.  Some clients will cling to the 3x3 for grim death before dropping back to a much close 2x2 access point.

 

 

I'm looking forward to @Uberseehandel response.  I'm certain it will be much more considered than my response, which is mostly personal opinion.

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