The laptop would often connect to the SSID but the laptop would be unable to get a webpage to render with all IP traffic essentially stalling. ICMP ping times would jump from 1 ms to 3,900 ms with multiple dropped packets scattered all about the constant ping. Without any load you could occasionally get 1 ms response times for a couple of minutes at a time but the instant you opened a web page the traffic would stall and the ICMP pings would start timing out.

The Intel engineer that was assisting me provided the hint, letting me know that Cisco IT had actually stumbled across this very same issue the week earlier internally with their own employees. Cisco had intentionally disabled A-MPDU on their WLCs, the workaround was to enable A-MPDU for 802.11n on their WLCs. I went ahead and checked our WLCs and sure enough we also had A-MPDU disabled – not exactly sure who or why it was disabled.

802.11n Status: 
    A-MPDU Tx: 
        Priority 0............................... Disabled 
        Priority 1............................... Disabled 
        Priority 2............................... Disabled 
        Priority 3............................... Disabled 
        Priority 4............................... Disabled 
        Priority 5............................... Disabled 
        Priority 6............................... Disabled 
        Priority 7............................... Disabled 
        Aggregation scheduler.................... Enabled 
        Frame Burst.............................. Automatic 
            Realtime Timeout..................... 10 
    A-MSDU Tx: 
        Priority 0............................... Enabled 
        Priority 1............................... Enabled 
        Priority 2............................... Enabled 
        Priority 3............................... Enabled 
        Priority 4............................... Enabled 
        Priority 5............................... Enabled 
        Priority 6............................... Disabled 
        Priority 7............................... Disabled 
    Rifs Rx ..................................... Enabled 
    Guard Interval .............................. Any 

I used the following CLI commands to enable A-MPDU; (note that I had to temporarily disable the 802.11a network to make the change – you’ll want to schedule this off-hours)

config 802.11a disable 
y 
config 802.11a 11nsupport a-mpdu tx priority 0 enable 
config 802.11a 11nsupport a-mpdu tx priority 1 enable 
config 802.11a 11nsupport a-mpdu tx priority 2 enable 
config 802.11a 11nsupport a-mpdu tx priority 3 enable 
config 802.11a 11nsupport a-mpdu tx priority 4 enable 
config 802.11a 11nsupport a-mpdu tx priority 5 enable 
config 802.11a enable 

Why doesn’t the Intel AC 8260 wireless adapter negotiate using A-MSDU?

I hope to be able to bring you that answer from either Cisco or Intel.

I hope you enjoyed the article Tim.

Cheers!

Update: December 7, 2016

Intel has released a new driver for the AC 8260 that is designed to address the issue.
https://downloadcenter.intel.com/download/26465/Intel-PROSet-Wireless-Software-and-Drivers-for-Windows-10
https://downloadcenter.intel.com/download/26469/Intel-PROSet-Wireless-Software-and-Drivers-for-IT-Admins

I’m currently testing the driver but haven’t had enough time to comment yet.

This week right in the middle of a fiber cut that left me with multiple Internet and Metro Ethernet circuits down the Seagate Momentus Thin hard drive in my Lenovo T430 ThinkPad up and died on me. Like a typical user I had left notes and documents on the C: drive that I hadn’t copied to either SharePoint, OneDrive or my team’s network share. A scramble ensued and I was ultimately able to recover the few files that I desperately wanted. One of those files included all my notes on building GSLB VIPs across a pair of A10 vThunder appliances – look for that post soon. I can still recall my younger days and the excitement that would ensue around rebuilding my desktop or laptop. Windows would generally slow down over time due to application and registry glut so a rebuild would usually result in a much better performing machine. I’m definitely not young anymore nor do I have the time, or patience, to be rebuilding my laptop or desktop.

The desktop team quickly replaced my hard drive but I took a minute and thought, “this is a great time to upgrade to a SSD“. I don’t run the corporate desktop image, instead I dual boot between Windows 8.1 (custom install) and Ubuntu 14, so while the desktop team had quickly replaced my failed hard drive I now needed to rebuild my entire machine along with all my applications, configurations, license keys, etc. If I’m going to spend all this time and effort I need to get something out of it – so I upgraded to an Intel 730 Series 240GB SSD. The Lenovo T430 ThinkPad only allows for 7mm think drives so you need to be mindful of that small detail when selecting a SSD that will physically fit into the laptop. I went ahead and started rebuilding the laptop using the Seagate hard drive – I couldn’t really wait even for the day it took NewEgg to ship the SSD to my house from New Jersey. When the Intel 730 arrived I performed a System Image Backup of Windows 8.1 to an external hard disk, installed the SSD, booted from a Windows 8.1 USB recovery stick and restored the backup to the SSD. The laptop booted the first time without issue, I installed the Intel SSD utilities to optimize the configuration (enable TRIM, etc) and the upgrade was complete. While the Lenovo T430 ThinkPad is no power house it gets the job done for me.

I’ve been slowly exploring Microsoft OneDrive and OneNote. Until a few years ago I would continually leave all sorts of paper notes all over my desk, eventually I migrated to just using Notepad which resulted in me leaving text documents all over my desktop or home drive. Very difficult to organize, somewhat difficult to search. I just started using Microsoft’s OneNote using OneDrive to store the documents. Hopefully this will help me organize my notes better and ultimately make me more efficient.

Cheers!