SLOW INTERNET ACCESS

When response times for key Internet-based systems go up over 30 seconds

CLIENT: UK INSURANCE COMPANY

CHALLENGE

Our customer has over 1,000 users using thin client terminals at multiple offices around the UK and they rely on Internet-based systems for many core business processes.

Intermittently, response times on these systems increased to over 30 seconds.

ENVIRONMENT


The key components are as follows:

  • Client PCs and Xen servers using Internet Explorer
  • Windows Active Directory domain controllers
  • Bluecoat proxy servers

All components except physical desktops are based in the two corporate data centres.

ANALYSIS

We analysed several examples of the problem and found that, while response times for web requests (HTTP/HTTPS) were good, the client PC was sending DNS requests for every element on the page – many of these requests were failing.

We then focused on the DNS performance and analysed several hours of DNS requests on the outside of the proxy servers:

And on the inside of the proxy servers:

This clearly showed that the delays were in the proxy server

SOLUTION

The response time problem was a combination of three factors:

  • IP Phones were trying to access the Internet but DNS was not fully configured for this
  • A logging change on the Proxy servers caused its DNS service to become saturated
  • A configuration change in the Proxy Auto-Configuration (PAC) file caused desktop PCs and Xen servers to send superfluous DNS requests which were then affected by the Proxy DNS issue

The desktop support team put in a workaround which stopped the superfluous DNS requests.

The underlying problem was then fixed by the proxy server support team.

SOLUTIONS USED ON THIS PROJECT

Performance & Reliability Troubleshooting

When response times for key Internet-based systems go up over 30 seconds

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