Problem with very low data transfer only to AWS SRV (all locations) - the problem concerns the source IP only my pool of external addresses

Based on your detailed description, it appears you're experiencing a specific network performance issue affecting TCP/443 uploads from your IP prefix to AWS services. This asymmetric behavior (normal downloads but severely limited uploads) is unusual and suggests several possible causes.

Since the issue:

• Only affects your specific IP prefix
• Persists across different ISPs and locations
• Occurs even with network equipment removed
• Started at a specific point in time (August 2025)
• Only impacts TCP/443 uploads while UDP performs normally
• Shows normal performance when testing from other IP ranges

This strongly suggests some form of traffic management or filtering specifically targeting your IP range. Here are the most likely possibilities:

1. Reputation-based filtering: AWS may have flagged your IP prefix in their threat intelligence systems. This could happen if the IP range was previously associated with abusive behavior, even if it wasn't from your organization.

2. DDoS protection mechanisms: AWS Shield or similar protection services might be applying throttling to your prefix based on historical traffic patterns.

3. TCP-specific network path issues: The fact that UDP works normally while TCP/443 is affected points to possible TCP window size issues or TCP-specific filtering along the network path.

4. Regional routing problems: There could be suboptimal routing between your network and AWS edge locations, causing TCP performance degradation over high-latency paths.

To resolve this issue, I recommend:

1. Contact AWS Support directly with your specific IP prefix information. They can check internal systems for any reputation flags or filtering policies.

2. Request AWS to review logs for any automated protection systems that might be throttling traffic from your prefix.

3. If possible, try testing with different TCP ports to see if the issue is specific to port 443 or affects all TCP traffic.

4. Consider implementing AWS S3 Transfer Acceleration if you're transferring data to S3, as this uses different network paths through AWS edge locations.

5. Try adjusting TCP window sizes and other TCP optimization parameters if you have control over the sending systems.

This appears to be a specific case that will require direct investigation by AWS network engineers with access to their internal systems.
Sources
The outbound speed from us-east-1 to Hong Kong is super slow. Serving website and download using Winscp is slow. The upload is normal or close to normal though. | AWS re:Post
S3 Transfer Rates Capped at 2.8mb/s ??? How Can I Speed This Up? | AWS re:Post