Version

All Versions

Date

Thursday, 11 February 2016

Summary

Some countries may give false results when testing websites with Argent Sentry

To elaborate, different ISPs in different countries may cause websites that are actually down to appear up, or vice versa

Technical Background

There are a plethora of reasons for this, but the common ones include:

• DNS issues, or outdated/erroneous/cached DNS entries in an ISP
• Network hops or routes from one ISP or country differs from routes from another country — one route is down while the other is up
• Country or IP-specific firewall settings (example: Great Firewall of China)

Resolution

The only real solution is to test public-facing websites from multiple location around the world, strategically deploying Trusted Agents or Daughter Engines in regions that cover the intended demographic

Additionally, if the website can be accessed using the IP address as the hostname, then DNS-related issues can be circumvented altogether