AWS ELB(NLB)

Overview

• Operates at OSI Level 4 (connection level)
  • TCP: IP + Port
  • Level 3 would be just IP
• Full control over IP addresses
  • Single IP address per AZ (VPC subnet)
    • EIP possible to attach
    • No CNAME resolution
• Long-running connections (months) supported
  • Normally idles after timeout
  • Use cases: IoT, gaming, messaging
  • No idle-timeout configuration
• Zonality 
  • No cross-zone balancing
    • But fails over to another AZ if all targets unhealthy (Route 53)

Limitations

• No SSL termination
• No Backend server encryption

Types

• Internet-facing
• Internal

Target Types

• Instance Id or IP (just like ALB)

Performance

• Scales to millions of requests
• Very low latency
• Handles volatile traffic well
  • Sudden spike (e.g. "flash sales")

Client source IP

• Unlike other ELB it preserves source IP address
• Only applies to targets registered by instance ID (not IP targerts)
• Proxy Protocol still available 
• No need for X-Forwarded-For

Monitoring 

• VPC flow logs (instead of access logs)
• CloudWatch

Healthchecks

• Network level
  • Observes normal (organic) traffic to target 
• Application level (like CLB/ALB)
  • Synthetic

Pricing

• NLCU
  • 100K active connections / minute
  • 800 new connections (flows) / second
  • 2.22 Mbps (1 GB / h)
• Highest dimension used (like in ALB)

References

• https://aws.amazon.com/elasticloadbalancing/details/#comparehttps://aws.amazon.com/elasticloadbalancing/details/#compare