Speed Test Question

[wrainwater]

I'm trying to troubleshoot a slow wireless speed issue. I have a client who complains about her wireless always slowing down in a certain area around our building. I cant replicate the issue. When I look at the MCS value the client has inside the controller it says m15 which according to the index chart means she is getting 300 mbps. I can confirm this by looking at the speed status of NIC card. My question is when I go to a site like speedtest.net and run it her download/upload speeds come back as 113 down and 180 up. Why does the controller say one thing and speed test another? am I misunderstanding how it works? Is the controller saying she has 300 MAX and speed test saying she is only using 113? 

thanks for any helpful input

[Philip D'Ath]

300Mb/s is the access rate.  If you are getting actual data throughput of 100Mb/s to 200Mb/s then that is a great result.

[wrainwater]

Thank you for your response. When you say access rate, what do you mean? Just the bandwidth that is available to use? and apparently we pay for a gig internet speed. so how is 100 mbps a great result in comparison? just trying to learn how all this works

[Philip D'Ath]

Check out this article about the issue:

https://documentation.meraki.com/MR/WiFi_Basics_and_Best_Practices/Wireless_Throughput_Calculations_and_Limitations

[wrainwater]

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Thanks, If Im understanding this quote correctly:

Limitations and Factors Affecting Throughput

First and foremost, throughput to the Internet is capped by the ISP and devices upstream of the APs. Also, 802.11 is a shared medium and is limited by other devices connected to the wireless. Therefore throughput should always be considered aggregate throughput. Interference (radio, physical, electrical) and the distance from client device to the Access Point are two major factors that have a negative impact on observed maximum throughput. Physical obstacles, other wireless networks and even everyday household devices like computers, microwaves, and televisions increase interference significantly, especially on the 2.4GHz band.

The half-duplex nature of wireless combined with other overhead also means that the actual aggregate throughput is typically 50 percent or less of the data rate. It is theoretically possible for 802.11n-capable wireless clients to achieve speeds as high as 100Mbps or more depending on the MIMO capabilities of the AP and the wireless client. However, wireless clients operating at 802.11b/g/a can cause 802.11n users to slow to less than 54Mbps because the radio must adjust to the lowest common denominator. 

The nature of WiFi technology makes throughput hard to predict. Therefore, network administrators should maintain reasonable expectations for connection speeds and keep the above factors in mind.

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What your saying is 300 mbps is the theoretical bandwidth limit my NIC card is capable of.  but with every hop towards the gateway, throughput is cut down by 50%. We have a switch hoping straight to the core which puts us at 1 hop to the gateway (cutting 300 down to 150%). Im assuming this is why clients are receiving the 100 mbps when its all said and done.  Did I understand this correctly? 

[patoberli · Accepted solution]

It basically means that with a 300 Mbps connection, you can realistically get around 160 Mbps, with perfect signals (no wireless neighbors).

What kind of AP are you using? 300 Mbps sounds like 802.11n standard. A new 802.11ac AP can offer ~1300 Mbps connection speed, which would equal up to 900 Mbps with a capable client (there are no notebook adapter that are capable). A typical notebook like yours would then connect with 866 Mbps, which would realistically mean around 450 Mbps transfer rate (again perfect signals).
This is always if only 1 user is either sending or receiving data. As soon as you have more than one user or mixed traffic, the speed will drastically get lower.

[wrainwater]

This made it all make sense. Thanks

[Leo Laohoo]

What is the model of the wireless NIC and what driver version is it running on?

[wrainwater]

Intel Dual Band Wireless AC 8260. Driver version 20.70.3.3