Outlook 2013/2016: How Microsoft Outlook (MAPI over HTTP) works with network delays

A long time ago I read an article of Neil Johnson on TechNet about research on the effects of network latency and different Outlook operating modes (Online, RPC/HTTP, Cached).
Since then, it took 8 years, changed several generations of server client applications and most important is that Exchange now use newest "MAPI over HTTP" protocol. I propose to do several tests to check what has changed during this time.

As a generator of interference on the network, I used a simple, but very functional tool - http://jagt.github.io/clumsy/.



Infrastructure:

• Microsoft Exchange 2016 CU12 on premise.
• Microsoft Outlook 2016 (Online mode + MAPI over HTTP).
• Network 1 Gbit.

Each test lasted 5-6 minutes and consisted of the following parts:

• Run the Outlook.
• Change folder and mailbox.
• Send 1 email with attachment.
• Open the Address Book.
• Set/clear a category for email.
• Open emails.

Results

Network Issues simulator	Average ping to Exchange	Outlook Average Response	%	Feeling
-	0 ms	15 ms	-	OK
Lag 50 ms	71 ms	85 ms	120%	Small freezes
Lag 100 ms	121 ms	131 ms	108%	Noticeable freezes during the transition between folders and mailboxes
Lag 150 ms	170 ms	215 ms	126%	Uncomfortable freezes
Lag 200 ms	222 ms	244 ms	110%	Uncomfortable freezes
Lag 300 ms	319 ms	350 ms	110%	Uncomfortable freezes
Lag 400 ms	425 ms	430 ms	101%	Slooovly
Lag 600 ms	621 ms	651 ms	105%	Sloooooovly
Lag 800 ms	815 ms	921 ms	113%	Sloooooooovly
Lag 1000 ms	1015 ms	1183 ms	117%	Slooooooooovly
Lag 2000 ms	2019 ms	2373 ms	118%	Sloooooooooovly
Lag 2700 ms	2717 ms	3670 ms	135%	Slooooooooooovly. Time to time lost connection to Exchange.
Lag 2800 ms				Doesn’t work
Drop 5%	0 ms	18 ms	-	OK
Drop 10%	0 ms	17 ms	-	OK
Drop 20%	0 ms	28 ms	-	Noticeable freezes during the transition between folders and mailboxes
Drop 30%	0 ms	70 ms	-	Uncomfortable freezes. Time to time lost connection to Exchange.
Drop 40%	-	-	-	Mostly disconnected.
Drop 10% + Lag 100 ms	123 ms	278 ms	226%	Uncomfortable freezes during the transition between folders and mailboxes
Drop 20% + Lag 100 ms	121 ms	446 ms	369%	Uncomfortable freezes. Outlook may lost connection to Exchange.
Throttle 100 ms 10%	24 ms	41 ms	171%	Small freezes
Tamper 10%	-	-	-	Doesn’t work

Conclusions

• A user could use Outlook in Online mode with lag up to 100 ms without huge impact on performance.
• Outlook 2016 and "MAPI over HTTP" protocol can survive up to 10% packet loss.
• Outlook 2016 stops connecting to Exchange upon reaching latency 2800 ms (compared with 800 ms in Outlook 2010) and with the loss of more than 30% of packages.

Screenshots