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5.2.2. Optimizing VPN/Direct Connect Costs

Optimizing VPN and Direct Connect (DX) costs involves balancing bandwidth, performance, and usage patterns to select the most cost-effective hybrid cloud connectivity solution.

Scenario: You need to connect your on-premises data center to your AWS VPC. For a large data migration (several PBs) over several weeks, you choose AWS Direct Connect for the primary path. For regular, lower-volume operational traffic, you plan to use AWS Site-to-Site VPN.

For network specialists, managing the costs associated with connecting on-premises networks to AWS via VPN or Direct Connect is crucial. The choice and configuration of these services directly impact the overall bill.

Key Strategies for Optimizing VPN/Direct Connect Costs:
  • AWS Site-to-Site VPN:
    • Cost: Billed per hour the VPN connection is provisioned, plus data transfer over the public internet.
    • Optimization: More cost-effective for lower bandwidth needs or as a backup path. Pay only for the provisioned hour and standard internet egress rates.
  • AWS Direct Connect (DX):
    • Cost: Billed for port hours (for the DX connection itself) and data transfer out from AWS over the DX connection. Data transfer into AWS over DX is typically free.
    • Optimization: Can be more cost-effective for large volumes of data transfer out compared to public internet egress, as DX egress rates are typically lower. The break-even point depends on your data volume.
    • Port Speed Selection: Choose the appropriate port speed (e.g., 1 Gbps, 10 Gbps) based on your actual bandwidth needs.
    • Virtual Interfaces (VIFs): Using multiple VIFs on a single DX connection does not add to the port hour cost.
  • AWS Client VPN:
  • Monitoring Usage: Use AWS Cost Explorer to monitor data transfer costs for VPN and Direct Connect to identify optimization opportunities.
Practical Implementation: Monitoring DX Data Transfer Out (CloudWatch)
# 1. Get the Direct Connect connection ID
aws directconnect describe-connections --query "connections[?connectionName=='MyProdDXConnection'].connectionId" --output text

# 2. Get the CloudWatch metric for data transfer out
aws cloudwatch get-metric-statistics \
  --namespace AWS/DirectConnect \
  --metric-name ConnectionBpsEgress \
  --dimensions Name=ConnectionId,Value=dxcon-abcdefgh \
  --start-time 2023-10-01T00:00:00Z \
  --end-time 2023-10-31T23:59:59Z \
  --period 86400 \
  --statistic Average

⚠️ Common Pitfall: Over-provisioning Direct Connect bandwidth. If you purchase a 10 Gbps connection but only use 1 Gbps on average, you are paying for unused capacity.

Key Trade-Offs:
  • Bandwidth/Reliability vs. Cost: Higher bandwidth and more reliable connections (DX) come at a higher fixed cost. Lower bandwidth, less predictable connections (VPN) are cheaper.

Reflection Question: How does optimizing VPN and Direct Connect (DX) costs by balancing bandwidth, performance, and usage patterns (e.g., using DX for bulk transfers, VPN for operational traffic) fundamentally enable you to select the most cost-effective hybrid cloud connectivity solution?