Have you considered user protocol issues, higher up the stack where your NOC investigation can't see them? If TCP is not tuned, and detects TCP packets are dropping due to congestion, it drops (halves?) its transmit rate until all is well again. At a network operator level, you may have the L1 bandwidth ready and willing to tranport all the bits in sight, but just one poor TCP stack (old FTP? old SMB?) in the TCP roundtrip will throttle bits presented way down. I have on my desk here a badly configured example where poor TCP buffering drops throughput to 5% of expected. Well known issue, for IT folks in enterprises. Wireshark etc will easily let you see how fast user traffic is arriving. Just a thought.
Roy

*Roy Hirst* | 425-556-5773 | 425-324-0941 cell
XKL LLC | 12020 113th Ave NE, Suite 100 | Kirkland, WA 98034 | USA

On 12/9/2014 12:02 PM, Darden, Patrick wrote:
MTU should be automatically managed by the AnyConnect client.  With that said, have 
you done PMTUd (e.g. nmap --script path-mtu <dest-ip> from one endpoint to the 
next)?

I'd do a network map, working with your upstream provider, to identify and 
isolate variables.  E.g. to find media changes (wrt MTU changes/mismatches).
        --start with icmp traceroute
        --next do a udp traceroute
        --next do a tcp traceroute
        --each traceroute will give you a slightly different picture, some hops 
will respond to one but not another
        --try a vpn connection  from Upstream1 first, to see if it happens 
there.
        --try a vpn connection  from Upstream2 next, to see if it happens there.
        --try a vpn connection in reverse from Upstream2, then Upstream1, to 
see if the speed in one direction, via one or another portal, is faster.
        --continue to isolate networks, network devices, until you can find the 
point (e.g. advertisement injector) or process (e.g. MTU LCD or asymmetric 
routing) which is causing this.

--p

-----Original Message-----
From: NANOG [mailto:nanog-boun...@nanog.org] On Behalf Of Zachary McGibbon
Sent: Tuesday, December 09, 2014 1:42 PM
To: NANOG
Subject: [EXTERNAL]Cisco AnyConnect speed woes!

I'm looking for some input on a situation that has been plaguing our new 
AnyConnect VPN setup.  Any input would be valuable, we are at a loss for what 
the problem is.

We recently upgraded our VPN from our old Cisco 3000 VPN concentrators running 
PPTP and we are now running a pair of Cisco 5545x ASAs in an HA active/standby 
pair.

The big issue we are having is that many of our users are complaining of low 
speed when connected to the VPN.  We have done tons of troubleshooting with 
Cisco TAC and we still haven't found the root of our problem.

Some tests we have done:

    - We have tested changing MTU values
    - We have tried all combinations of encryption methods (SSL, TLS, IPSec,
    L2TP) with similar results
    - We have switched our active/standby boxes
    - We have tested on our spare 5545x box
    - We connected our spare box directly to our ISP with another IP address
    - We have whitelisted our VPN IP on our shaper (Cisco SCE8000) and our
    IPS (HP Tipping Point)
    - We have bypassed our Shaper and our IPS
    - We made sure that traffic from the routers talking to our ASAs is
    synchronous, OSPF was configured to load balance but this has been changed
    by changing the costs on the links to the ASAs
    - We have verified with our two ISPs that they are not doing any kind of
    filtering or shaping
    - We have noticed that in some instances that if a user is on a low
    speed connection that their VPN speed gets cut by about 1/3.  This doesn't
    seem normal that the VPN would use this much overhead
    - We do not have the issue when connecting to VPN directly on our own
    network, only connections from the Internet

If you have any ideas on what we could try net, please let me know!

- Zachary




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