Network Performance and Performance Issues

[gary_the_network_guy]

Hello everybody,

some users start to experience performance issues and of course it is shoved down to the networking team(just me) to determine and fix the issues. We have a very simple network design, basically there are two 4500series Layer3 switches in a vss-configuration(Collapsed Core). Performance Issues are experienced everywhere(Datacenter, VPN) but the most issues we are having with RDS(Remote Desktop Service), a lot of users experience constant connecting and reconnecting. My question is, how to determine where the issue is happening and what are the steps I could do, to tell if its a network problem or something else...

[Joseph W. Doherty]

Are the RDS users local, on LAN, or remote?

What all does the DC do, regarding large bulk data transfers, if any?

You mention VPN.  Kind of VPN, and is MTU issues possible?

What sup in your 4500s?  (I assume one of the later sup model, as you mention running VSS.)

Is everything multi-home, i.e. connections to both core VSS 4500s?

From the little information you've mentioned, RDS can be almost as sensitive to latency and/or drop issues as VoIP.  If you have interface congestion, QoS might be needed to guarantee RDS the service level it needs to work well.

As you also mention VPN, lots of possible issues there, when supporting highly sensitive traffic like RDS, but would really need to dig deep into your VPN's logical architecture.

VSS, if you're not fully dual connected, can bottleneck traffic if it passes it between VSS devices, which should never be the case except in case of partial hardware failure on one of the VSS devices.  Further, I recall (?) earlier VSS implementations didn't support full QoS between VSS devices.

As to next steps, excluding delving into VPN, check all interfaces for an increasing drop count.  On your VSS pair, check usage on cross link(s) (which should be almost non-existent).

[gary_the_network_guy]

Thank you very much, It will take some time to gather the information needed but I have PRTG as a tool to look into it. Also, there are some questions I can answer right now. 

1. RDS issues are experienced all across local, lan and remote. That's why I thought there were some isses with the servers.

2. Regarding bulk data, we have seperate fileservers.(I hope that answers your question, the DC does not do anything regarding bulk data)

3. Model WS-C4500X-32

4. Multi-Homed on Core? We have Datacenter switches, two 5000series nexus switches and some fex extenders.

[Joseph W. Doherty]

Did you check drop counts?

#4 Unsure we're on the same page.  By multi-home, I mean every device connecting to a VSS pair has a physical connection to each VSS member (and can accept traffic on that link).  You have that?

[gary_the_network_guy]

You mention VPN.  Kind of VPN, and is MTU issues possible?

The issues we experience are all with our mobile SSLVPN.

[Joseph W. Doherty]

Okay, and are MTU issues possible (due to VPN encapsulation overhead)?  If so, you've mitigated them?