Port Exhaustion and IIS 8 on Server 2012 R2

My company has a highly utilized web server running IIS
8.5 on Server 2012 R2

At any given time, there
are 34,000 connections to IIS and 200 requests per second. We also have an SFTP service
running on the machine that has an average of 100 connected users. Everyone once in a
while our monitoring system will timeout and FTP users are unable to connect. I've been
doing a lot of research on port exhaustion, however, I cannot find any definite
documentation on ephemeral port exhaustion with IIS.

From my understanding, when a connection is
made to the HTTP service, the response still comes from port 80, same with the FTP
service. We do run ASP.NET sites that connect REST services on the same box, I know
those connections would use an ephemeral port, but I'm not sure that it's using all
16,384.

I have used several scripts online to
detect port exhaustion
href="http://blogs.technet.com/b/clinth/archive/2013/08/09/detecting-ephemeral-port-exhaustion.aspx"
rel="nofollow
noreferrer">http://blogs.technet.com/b/clinth/archive/2013/08/09/detecting-ephemeral-port-exhaustion.aspx
- Script rarely shows any ephemeral port usage above 2%
href="http://blogs.msdn.com/b/debuggingtoolbox/archive/2010/10/11/powershell-script-troubleshooting-for-port-exhaustion-using-netstat.aspx"
rel="nofollow
noreferrer">http://blogs.msdn.com/b/debuggingtoolbox/archive/2010/10/11/powershell-script-troubleshooting-for-port-exhaustion-using-netstat.aspx
This
script will show some connections waiting for
ports.

Ports Used:
            35,084
Ports Waiting:
            654

Of the connections
waiting for a port, the following are from the local
machine

127.0.0.1 44 waiting of
            110 total
            (40%)

My
question is, is the server suffering from port exhaustion? When I export a netstat -n
and filter by ephemeral ports, I only see 286 in use. The Web Server (80 and 443)
account for 32,300 of the connections and FTP accounts for
450.

Is there a connection limit on IIS
8.5?

[edit]
Of the ports in use, here
is the breakdown by
state

ESTABLISHED
            32,394
TIME_WAIT 710
CLOSING 16

FIN_WAIT_1
            2
FIN_WAIT_2 3
LAST_ACK 14
SYN_RECEIVED
            238