AWS Site-to-Site VPN vs. Direct Connect: Choosing Your Path to the Cloud
For any organization running hybrid infrastructure, one of the first architectural decisions is: how does our data center actually talk to AWS? The two primary answers — Site-to-Site VPN and Direct Connect — solve the same fundamental problem but take very different roads to get there.
The Core Difference: Public Internet vs. Private Line
AWS Site-to-Site VPN builds an encrypted IPsec tunnel between your on-premises network and AWS over the public internet. Think of it as a secure, private conversation happening on a public street — the data is encrypted and protected, but it still travels across infrastructure you don't own or control.
AWS Direct Connect, by contrast, is a dedicated physical network connection running from your facility (or a colocation provider) directly into AWS — bypassing the public internet entirely. It's less like a secure conversation on a public street and more like a private, leased phone line that only you use.
Site-to-Site VPN in Detail
- Setup time: Hours. You can be up and running the same day, since no physical infrastructure is required.
- Cost: Low — pay-as-you-go pricing, no major upfront investment.
- Performance: Each tunnel caps out around 1.25 Gbps, and since it rides on the public internet, latency and throughput can vary depending on internet conditions.
- Security: Encrypted by default (IPsec).
- Best for: Quick deployments, smaller workloads, disaster recovery/failover links, or any situation where speed of setup matters more than guaranteed performance.
Direct Connect in Detail
- Setup time: Weeks to months. Typically requires coordination with an AWS Direct Connect Partner and physical cross-connects at a colocation facility.
- Cost: Higher — port-hour charges plus data transfer, though data transfer OUT is often cheaper than over VPN at scale.
- Performance: Consistent, predictable bandwidth from 50 Mbps up to 100 Gbps, with lower and more stable latency since it avoids the public internet entirely.
- Security: Private by nature (not encrypted by default — many enterprises layer a VPN on top for encryption).
- Best for: Large, consistent data transfers, latency-sensitive workloads (e.g., real-time applications, large-scale backups), and compliance requirements that favor avoiding the public internet.
The Best of Both Worlds
These two aren't always an either/or choice. A common enterprise pattern is:
- Direct Connect as the primary path for consistent performance and lower long-term data transfer costs
- Site-to-Site VPN as a backup/failover in case the dedicated line goes down
- Or even VPN over Direct Connect — layering IPsec encryption on top of the private connection for organizations that need both privacy and guaranteed encryption
Quick Reference
| Factor | Site-to-Site VPN | Direct Connect |
|---|---|---|
| Connectivity | Public internet (encrypted) | Dedicated private line |
| Setup time | Hours | Weeks–months |
| Cost | Low, pay-as-you-go | Higher, requires partner |
| Bandwidth | Up to ~1.25 Gbps/tunnel | 50 Mbps–100 Gbps |
| Latency | Variable | Consistent, low |
| Encryption | Built-in (IPsec) | Not by default |
Exam and Real-World Takeaway
If a scenario calls for fast, cheap, encrypted connectivity — reach for Site-to-Site VPN. If it calls for consistent low latency, high throughput, or avoiding the public internet — reach for Direct Connect. And if the scenario says "high availability" or "redundancy" for a hybrid connection, the answer is often: both, together.
Now here's a quick visual summary of how each path actually routes traffic:
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