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.

Question

I am experiencing severe asymmetric network performance on my Lightsail instance after migrating it from the Tokyo region to us-east-1. My access point is from Hong Kong.

Instance Domain: engjmanga.jdbwizard.com

Core Problem: Outbound traffic (downloads) from the server is extremely slow, while inbound traffic (uploads) is performing as expected.

Download Test: A 10 MB file download via WinSCP takes over 3 minutes. A 100 KB webpage takes over 50 seconds to load. This indicates an effective download speed of less than 60 KB/s.

Upload Test: The same 10 MB file uploads in under 10 seconds, indicating a normal upload speed of approximately 1 MB/s.

This is not a general latency issue, but a specific problem with the egress bandwidth or network path from us-east-1 to my network in Hong Kong. Please investigate potential throttling, routing, or peering issues on the return path.

re:Post Agent · Answer

The slow outbound speed from your us-east-1 Lightsail instance to Hong Kong appears to be a cross-region network performance issue. This asymmetric behavior (slow downloads but normal uploads) suggests several potential causes:

1. **Cross-region latency and network conditions**: The physical distance between us-east-1 (North Virginia) and Hong Kong creates inherent latency. Network conditions along this path may be experiencing congestion or suboptimal routing.

2. **Bandwidth limitations**: Your Lightsail instance may have bandwidth credits that are being consumed. EC2 and Lightsail instances have specific network bandwidth allocations based on their size.

3. **TCP window size optimization**: For high-latency connections like those between us-east-1 and Hong Kong, TCP window sizes may need optimization to achieve better throughput.

To troubleshoot and improve your situation:

1. **Check network performance**:
- Run an MTR test to identify potential packet loss or high latency points in the network path
- Use iperf3 to test TCP throughput with different window sizes (try 128K, 512K, and 1024K)

2. **Consider instance upgrades**:
- Larger instance sizes typically have better network performance
- Ensure your bandwidth credit is available for your instance

3. **Implement network optimizations**:
- Enable compression if supported by your transfer protocols
- Optimize TCP window sizes for high-latency connections
- Consider using a CDN like CloudFront to cache and deliver your website content from edge locations closer to Hong Kong

4. **Alternative solutions**:
- If this is a persistent issue, consider migrating back to the Tokyo region or to a region closer to Hong Kong
- For website content, implementing Amazon CloudFront would significantly improve performance by serving content from edge locations closer to your users

The asymmetric performance strongly suggests this is related to the network path between AWS us-east-1 and Hong Kong rather than an issue with your instance itself.  
**Sources**  
[Troubleshoot low transfer speed on Site-to-Site VPN | AWS re:Post](https://repost.aws/knowledge-center/vpn-site-to-site-low-transfer-speed)  
[how can I improve the bandwidth? | AWS re:Post](https://repost.aws/questions/QUi6ypAgc5QUyqSbDorChTmg/how-can-i-improve-the-bandwidth)  
[Troubleshoot cross-region transfer issues - AWS Transfer Family](https://docs.aws.amazon.com/transfer/latest/userguide/cross-region-transfer-issues.html)  
[Troubleshoot SFTP connector issues - AWS Transfer Family](https://docs.aws.amazon.com/transfer/latest/userguide/connector-troubleshooting.html)  
[transfer-family-network-issues | AWS re:Post](https://repost.aws/knowledge-center/transfer-family-network-issues)

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.

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