Building from the FoundationsThe Physical Reality of the CloudSection 5.1: Layer 1 (Physical): Redundant Circuits and Direct Connect ModelsWhy Direct Connect Belongs in Layer 1Failure Modes Are Physical FirstThe Direct Connect Resiliency Patterns—Read As Physical, Not LogicalDXGW As Blast-Radius Containment, Physically ExpressedCommissioning, Acceptance, and Monitoring—Treat the Glass As ObservableHosted vs. Dedicated—What Changes PhysicallyThe Internet Is Not the Enemy—Use It As Physical InsuranceWhat Not to Do at Layer 1The Layer-1 Contract with the Layers AboveSection 5.2: Layer 2 (Data Link): LAGs and Active/Standby Failover in Hybrid LinksTurning Many into One: Link Aggregation GroupsFlow Distribution and Member Failure BehaviorSegmentation, Frame Integrity, and Link-Layer ProtectionVLANs (IEEE 802.1Q)—Isolation on Shared WiresMTU and Jumbo Frames—Size MattersMACsec—Protecting the Hop at Layer 2Bringing It All TogetherSection 5.3: Layer 3 (Network): BGP Path Selection, AWS TGW, DX + VPN BackupIntroduction to BGP in AWS and Hybrid ArchitecturesHow BGP Thinks: Attributes That Shape ResilienceBGP in the AWS Hybrid EdgeOperational Simplicity As a Resilience StrategyThe Convergence ImperativeDX + VPN Hybrid Failover PatternsClosing Thoughts for Section 5.3Section 5.4: Layer 4 (Transport): Load Balancing Strategies in AWS (NLB) and Session ContinuityFrom Reachability to Reliability: How Transport Protocols Create ResilienceNetwork Load Balancer: Keeping Flows Consistent Through DisruptionGateway Load Balancer in an Inspection VPCThe Inspection VPC PatternFrom Transport Integrity to Application AwarenessSection 5.5: Layer 7 (Application): Rate Limiting, Caching, and Failover Logic (ALB)Connection Semantics at the EdgeShaping Load Before It Hurts: Rate Limiting and Back-PressureBuying Time with Distance: Caching As a Resilience PrimitiveFailover Where Users Notice: ALB Routing, Health, and Steady HandoversPutting the Pieces TogetherOperational Checklist: Making Layer-7 Resilience RealFrom Layers to BoundariesLessons Learned from Chapter 5Looking Ahead—From Layers to Boundaries
