如何降低AWS部署的移动端OpenVPN服务器带宽成本？

Hey there, let's tackle your questions head-on given your setup: AWS-hosted OpenVPN on Ubuntu 18.04, mobile clients, a single instance handling up to 300 users with zero CPU/memory issues—but bandwidth costs blowing past $1000/month. Here's what you need to know:

Since bandwidth is your main cost driver, focus on optimizing AWS data transfer costs first:

• Pick a Cheaper AWS Region: Outbound bandwidth pricing varies a lot by region. For example, Ohio (us-east-2) or Mumbai (ap-south-1) have lower rates than pricier regions like Northern Virginia (us-east-1). If your user base is clustered in a specific area, moving your instance there can slash bandwidth bills immediately.
• Dig Into Bandwidth Usage with Cost Explorer: Use AWS Cost Explorer to break down your data transfer costs. Look for spikes or top-consuming IPs—you might find some users are using your VPN for large downloads, P2P traffic, or streaming that’s driving up costs. This lets you target those users or block high-bandwidth activities.
• Lock in Instance Savings: Even though bandwidth is the big ticket, switching your on-demand EC2 instance to a Reserved Instance (RI) or Savings Plan can cut your base instance cost by 30-70% over time. Every bit adds up.
• Negotiate Enterprise Discounts: If you’re pushing multiple TBs of data monthly, reach out to AWS sales to discuss enterprise pricing. They often offer discounts for high-volume, long-term customers.

Let’s clarify what’s allowed and what you need to watch for:

• AWS TOS Compliance: Running OpenVPN on EC2 is fully permitted under AWS’s Terms of Service, as long as you’re not using it for illegal activities (hacking, copyright infringement, etc.). AWS doesn’t restrict legitimate VPN services.
• Regional Legal Rules: The biggest compliance risk depends on your users’ locations. Some countries (like China, Russia, UAE) have strict VPN regulations—you need to make sure your service doesn’t violate local laws where your users are based. For EU users, you’ll need to follow GDPR: have a clear privacy policy, inform users about any data you collect via the VPN, and ensure data transfers are compliant.
• Protect Yourself with User Agreements: Add clauses to your user agreement that prohibit misuse of the VPN (like copyright infringement, P2P sharing, or illegal acts). This shields you from liability if users break laws using your service.

Here’s how to cut down on bandwidth per user without sacrificing performance:

• Enable LZ4 Compression: OpenVPN supports LZ4, a fast, efficient compression algorithm perfect for mobile traffic. Add compress lz4-v2 to your /etc/openvpn/server.conf file, and make sure your mobile clients have compression enabled (most modern apps do this by default). This can reduce bandwidth usage by 30-50% for text or already compressed content.
• Fix MTU Issues with MSS Clamping: Mobile networks often have smaller MTU sizes, leading to packet fragmentation and wasted bandwidth. Add mssfix 1300 to your server config to limit TCP segment size, reducing retransmissions and overhead.
• Limit Bandwidth Per Client: Use OpenVPN’s client config directory to set rate limits for individual users. Create a client-config-dir in your OpenVPN setup, then for each client, add a file with push "rate-limit 10240 20480" (limits to 10MB/s sustained, 20MB/s burst—adjust values to fit your needs). This stops heavy users from hogging all the bandwidth.
• Block High-Bandwidth Services: Use iptables on your Ubuntu server to block access to unnecessary high-bandwidth services. For example, block P2P ports (6881-6889) with:

  iptables -A OUTPUT -p udp --dport 6881:6889 -j DROP
  

  Or block streaming sites if they’re not part of your users’ intended use case.
• Advise Users on Mobile Best Practices: Tell your users to enable VPN only when needed, use Wi-Fi instead of mobile data whenever possible, and turn off background app sync while connected. Many mobile VPN apps also have a "low data mode" that reduces bandwidth usage automatically.

内容的提问来源于stack exchange，提问作者Yona