Desperate: How to definitively prove ISP throttling?

I completely understand how frustrating cripplingly slow SaaS upload speeds are; it directly impacts user experience and your bottom line. We’ve faced similar issues with clients trying to push large creative assets or data syncs, and proving ISP throttling can be a challenge, but it’s definitely achievable with the right methodology.

Before directly accusing your ISP, ensure you've ruled out internal network performance monitoring issues. Check your router/firewall logs, ensure QoS isn't misconfigured internally, and verify your server isn't overloaded or bottlenecked on its own egress.

To get undeniable proof, you need comparative data and specific diagnostic tools:

1. Establish a Baseline from Multiple External Points:

   Your first step is to definitively prove that the issue is unique to your business internet connection. Perform simultaneous upload speed tests from:

   • Your office network (the one experiencing issues).
   • A completely different network (e.g., a home fiber connection, a co-working space, or even a cloud-based VM with a known good connection).
   • Use reliable tools like Speedtest.net and Fast.com for general bandwidth testing, but also consider uploading a large, consistent file (e.g., 500MB - 1GB) to a neutral cloud storage provider (like S3, Google Cloud Storage, or Azure Blob Storage) and record the transfer rates. Repeat this several times at different times of the day.

2. The VPN Test (Strong Indicator of Throttling):

   This is often the most direct way to detect protocol-specific throttling or traffic shaping. Connect to a reputable, high-speed VPN service (e.g., NordVPN, ExpressVPN, ProtonVPN) from your office network. Then, repeat your upload tests (both general speed tests and the large file upload to cloud storage). If your upload speeds significantly improve while connected to the VPN, it's a very strong indication that your ISP is throttling specific types of traffic that are no longer identifiable when encapsulated by the VPN.

3. Specialized Throttling Detection Tools (M-Lab):

   The Measurement Lab (M-Lab) provides several excellent, academically-backed tools for network diagnostics, which are often accepted as credible evidence:

   • NDT (Network Diagnostic Tool): While primarily for general network performance, it can detect some forms of congestion and misconfiguration.
   • Glasnost: This tool is specifically designed to test for application-specific throttling. It attempts to transfer data using different protocols (e.g., BitTorrent, HTTP) and compares speeds to detect if certain traffic types are being deliberately slowed down. This is particularly useful if your SaaS uses specific ports or protocols that might be targeted.
   • Access these tools via Measurement Lab's website.

4. Deep Packet Inspection with Wireshark:

   For highly technical proof, a Wireshark capture during a slow upload can reveal a lot. Look for:

   • High retransmission rates: Indicates dropped packets, which could be due to congestion or deliberate packet shaping.
   • TCP Window Size issues: A consistently small receive window could indicate congestion or a bottleneck.
   • Connection resets: As seen in your logs, this is a critical indicator. Analyzing the packet flow leading up to the reset can pinpoint the exact cause or where the reset originates.

   This requires some expertise to interpret, but the raw data is very difficult for an ISP to dispute.

5. Continuous Monitoring & Documentation:

   Single tests are good, but consistent data over time is better. Set up a script or use a network monitoring tool (like PRTG, Zabbix, or even a simple cron job using curl or wget to upload a file periodically) to log upload speeds every 15-30 minutes for a few days. This will show patterns of degradation and help you correlate it with specific times or activities.

   Keep meticulous records: timestamps, tool used, results (screenshots are helpful), and whether a VPN was active. The more data you have, the stronger your case will be when you present it to your ISP.

Mustafa Ali, wow, this is incredibly thorough. I was just looking for a quick fix but your breakdown on establishing baselines and using VPNs really shows me the importance of systematic proof. Ngl, it's a whole different level of troubleshooting I hadn't even considered.