A Network Load Balancer (NLB) is a Layer 4 load balancing solution offered by AWS that operates at the transport layer, handling TCP, UDP, and TLS traffic. It is designed for high-performance, low-latency applications requiring extreme scalability and reliability.
Key features of NLB for reliabili…A Network Load Balancer (NLB) is a Layer 4 load balancing solution offered by AWS that operates at the transport layer, handling TCP, UDP, and TLS traffic. It is designed for high-performance, low-latency applications requiring extreme scalability and reliability.
Key features of NLB for reliability and business continuity include:
**Ultra-High Performance**: NLB can handle millions of requests per second while maintaining ultra-low latencies, making it ideal for mission-critical applications that demand consistent performance.
**Static IP Addresses**: Each NLB provides a static IP address per Availability Zone, which is essential for applications requiring fixed endpoints. You can also assign Elastic IP addresses for whitelisting purposes.
**Cross-Zone Load Balancing**: NLB distributes traffic across registered targets in all enabled Availability Zones, ensuring even distribution and enhanced fault tolerance.
**Health Checks**: NLB performs health checks on targets to ensure traffic is only routed to healthy instances. This automatic detection and rerouting capability is crucial for maintaining application availability.
**Availability Zone Failover**: When targets in one Availability Zone become unhealthy, NLB automatically routes traffic to healthy targets in other zones, providing seamless failover capabilities.
**Preserve Source IP**: NLB preserves the client source IP address, which is valuable for logging, security analysis, and applications requiring client identification.
**Integration with AWS Services**: NLB integrates with Auto Scaling groups, ensuring that as demand increases, additional instances are registered automatically. It also works with AWS PrivateLink for private connectivity.
**TLS Termination**: NLB supports TLS termination, offloading encryption and decryption work from your application servers.
For business continuity, NLB provides a highly available architecture by distributing traffic across multiple targets and Availability Zones. Combined with proper target group configuration and health check settings, NLB ensures your applications remain accessible even during infrastructure failures or maintenance windows.
Network Load Balancer is a critical component for high-performance applications requiring ultra-low latency and the ability to handle millions of requests per second. For the AWS SysOps Administrator Associate exam, understanding NLB is essential because it directly relates to reliability, business continuity, and ensuring applications remain available under extreme traffic conditions.
What is a Network Load Balancer?
Network Load Balancer operates at Layer 4 (Transport Layer) of the OSI model, handling TCP, UDP, and TLS traffic. It is designed for extreme performance scenarios where latency must be minimized. Key characteristics include:
• Static IP addresses: Each NLB can have one static IP per Availability Zone, and you can assign Elastic IPs • Ultra-low latency: Capable of handling millions of requests per second with latencies in the microseconds • Preserves source IP: The client's source IP is preserved and passed to targets • Cross-zone load balancing: Disabled by default (unlike ALB) • Health checks: Supports TCP, HTTP, and HTTPS health checks
How Network Load Balancer Works
1. Connection Flow: Client requests arrive at the NLB, which routes traffic based on IP protocol data (TCP/UDP port and IP address)
2. Target Groups: NLB forwards requests to registered targets such as EC2 instances, IP addresses, or Application Load Balancers
3. Listener Configuration: You configure listeners on specific ports and protocols (TCP, UDP, TLS) to check for connection requests
4. Zonal Isolation: When cross-zone load balancing is disabled, each load balancer node distributes traffic only to targets in its Availability Zone
5. TLS Termination: NLB can terminate TLS connections, offloading encryption work from backend instances
Key NLB Features for the Exam
• Sticky Sessions: Supported using source IP affinity • Connection Draining: Called deregistration delay, allowing in-flight requests to complete • PrivateLink Support: NLB is required for exposing services via AWS PrivateLink • Zonal DNS: Provides DNS names for each AZ for zonal isolation • Long-lived TCP connections: Ideal for WebSocket and IoT applications
Exam Tips: Answering Questions on Network Load Balancer
Tip 1: When a question mentions millions of requests per second or extreme performance, think NLB first.
Tip 2: If the scenario requires a static IP address or Elastic IP for a load balancer, NLB is the correct answer. ALB does not support static IPs.
Tip 3: Questions about TCP/UDP traffic or non-HTTP protocols point toward NLB. ALB only handles HTTP/HTTPS.
Tip 4: When you see AWS PrivateLink or exposing services to other VPCs, remember that NLB is required.
Tip 5: If the question asks about preserving the client source IP at Layer 4, NLB is the solution.
Tip 6: Remember that cross-zone load balancing is disabled by default for NLB but enabled by default for ALB. This is a common exam question.
Tip 7: For gaming, IoT, or real-time applications requiring persistent TCP connections, NLB is preferred.
Tip 8: If a question mentions needing to handle sudden traffic spikes or volatile workloads, NLB scales better than CLB.
Common Exam Scenarios
• Migrating from Classic Load Balancer to modern load balancers for TCP traffic → Use NLB • Providing a consistent IP for whitelisting by partners → Use NLB with Elastic IPs • Connecting on-premises applications via VPN needing low latency → NLB • Hybrid architectures using IP addresses as targets → NLB supports IP targets