Architecture Overview

Comprehensive architecture documentation for AWS Control Tower Landing Zone.

Table of contents

1. System Architecture
   1. High-Level Architecture
2. Core Components
   1. 1. Control Tower Landing Zone
   2. 2. Organizational Units
   3. 3. Service Control Policies
3. Network Architecture
   1. Transit Gateway Hub
   2. Network Firewall
   3. Zero Trust Architecture
4. Security Architecture
   1. Defense in Depth
   2. Security Services
5. Data Flow
   1. Logging Pipeline
   2. Security Event Flow
6. Deployment Architecture
   1. Terraform State Management
   2. CI/CD Pipeline
7. Scalability
   1. Horizontal Scaling
   2. Vertical Scaling
8. High Availability
   1. Multi-AZ Deployment
   2. Disaster Recovery
9. Related Documentation

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System Architecture

The AWS Control Tower Landing Zone implements a multi-account architecture with comprehensive security, networking, and governance controls.

High-Level Architecture

┌─────────────────────────────────────────────────────────────────┐
│                      Management Account                          │
│  ┌────────────────────────────────────────────────────────────┐ │
│  │              Control Tower Landing Zone                    │ │
│  │                                                            │ │
│  │  • GuardDuty          • Security Hub    • AWS Config     │ │
│  │  • CloudTrail         • Network Firewall                 │ │
│  │  • Transit Gateway    • KMS Encryption                   │ │
│  └────────────────────────────────────────────────────────────┘ │
└──────────────────────────┬───────────────────────────────────────┘
                           │
        ┌──────────────────┴──────────────────┐
        │                                     │
┌───────▼────────┐                   ┌────────▼───────┐
│  Security OU   │                   │  Workload OUs  │
│                │                   │                │
│  • Log Archive │                   │  • Production  │
│  • Audit       │                   │  • Non-Prod    │
│  • Security    │                   │  • Development │
└────────────────┘                   └────────────────┘

---

Core Components

1. Control Tower Landing Zone

The foundation of the multi-account environment:

• Automated Setup - Terraform-based deployment
• Account Factory - Automated account provisioning
• Guardrails - Preventive and detective controls
• Dashboard - Centralized monitoring

2. Organizational Units

Hierarchical structure for account organization:

Root
├── Security OU
│   ├── Log Archive Account
│   ├── Audit Account
│   └── Security Tooling Account
├── Infrastructure OU
│   ├── Network Account
│   └── Shared Services Account
├── Production OU
│   └── Production Workload Accounts
├── Non-Production OU
│   ├── Staging Accounts
│   └── Development Accounts
├── Sandbox OU
│   └── Sandbox Accounts
└── Suspended OU
    └── Decommissioned Accounts

3. Service Control Policies

35+ SCPs for governance:

• Security Controls - MFA, encryption, region restrictions
• Cost Controls - Instance type restrictions, resource limits
• Compliance Controls - Audit logging, data residency
• Operational Controls - Service restrictions, API limits

---

Network Architecture

Transit Gateway Hub

Centralized network connectivity:

┌─────────────────────────────────────────────────────────┐
│                   Transit Gateway                        │
│                                                          │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐ │
│  │  Inspection  │  │    Egress    │  │   Workload   │ │
│  │     VPC      │  │     VPC      │  │     VPCs     │ │
│  └──────────────┘  └──────────────┘  └──────────────┘ │
│         │                 │                  │          │
│         └─────────────────┴──────────────────┘          │
└─────────────────────────────────────────────────────────┘

Network Firewall

Stateful inspection and filtering:

• Inspection VPC - Centralized traffic inspection
• Firewall Rules - Domain filtering, IPS/IDS
• Logging - Flow logs and alert logs
• High Availability - Multi-AZ deployment

Zero Trust Architecture

Deny-by-default security model:

• Explicit Allow - All traffic explicitly allowed
• Least Privilege - Minimal required access
• Micro-segmentation - Granular network controls
• Continuous Verification - Ongoing validation

---

Security Architecture

Defense in Depth

Multiple layers of security controls:

┌─────────────────────────────────────────────────────────┐
│ Layer 7: Governance (SCPs, AWS Organizations)           │
├─────────────────────────────────────────────────────────┤
│ Layer 6: Identity (IAM, SSO, MFA)                      │
├─────────────────────────────────────────────────────────┤
│ Layer 5: Application (WAF, API Gateway)                │
├─────────────────────────────────────────────────────────┤
│ Layer 4: Data (KMS, Encryption, DLP)                   │
├─────────────────────────────────────────────────────────┤
│ Layer 3: Network (Firewall, Security Groups, NACLs)    │
├─────────────────────────────────────────────────────────┤
│ Layer 2: Compute (GuardDuty, Inspector, Patch Mgmt)    │
├─────────────────────────────────────────────────────────┤
│ Layer 1: Physical (AWS Data Centers)                   │
└─────────────────────────────────────────────────────────┘

Security Services

• GuardDuty - Threat detection
• Security Hub - Security posture management
• AWS Config - Configuration compliance
• IAM Access Analyzer - Access analysis
• CloudTrail - API activity logging
• VPC Flow Logs - Network traffic logging

---

Data Flow

Logging Pipeline

┌──────────────┐
│   Services   │
└──────┬───────┘
       │
       ▼
┌──────────────┐
│  CloudWatch  │
│     Logs     │
└──────┬───────┘
       │
       ▼
┌──────────────┐
│  S3 Bucket   │
│  (Encrypted) │
└──────┬───────┘
       │
       ▼
┌──────────────┐
│   Glacier    │
│  (Archive)   │
└──────────────┘

Security Event Flow

┌──────────────┐
│   Security   │
│    Event     │
└──────┬───────┘
       │
       ▼
┌──────────────┐
│  EventBridge │
└──────┬───────┘
       │
       ├──────────────────┐
       │                  │
       ▼                  ▼
┌──────────────┐   ┌──────────────┐
│     SNS      │   │    Lambda    │
│ Notification │   │  Remediation │
└──────────────┘   └──────────────┘

---

Deployment Architecture

Terraform State Management

┌──────────────────────────────────────────────────────┐
│                  S3 Backend                          │
│                                                      │
│  • State File (encrypted with KMS)                  │
│  • Native State Locking (Terraform 1.6+)           │
│  • Versioning Enabled                               │
│  • Cross-Region Replication (optional)              │
└──────────────────────────────────────────────────────┘

CI/CD Pipeline

┌──────────────┐
│  Developer   │
│    Commit    │
└──────┬───────┘
       │
       ▼
┌──────────────┐
│  Pre-Commit  │
│    Hooks     │
└──────┬───────┘
       │
       ▼
┌──────────────┐
│   GitHub     │
│   Actions    │
└──────┬───────┘
       │
       ├──────────────────┬──────────────────┐
       │                  │                  │
       ▼                  ▼                  ▼
┌──────────────┐   ┌──────────────┐   ┌──────────────┐
│  Validation  │   │   Security   │   │  OPA Tests   │
│              │   │   Scanning   │   │              │
└──────┬───────┘   └──────┬───────┘   └──────┬───────┘
       │                  │                  │
       └──────────────────┴──────────────────┘
                          │
                          ▼
                   ┌──────────────┐
                   │   Terraform  │
                   │     Apply    │
                   └──────────────┘

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Scalability

Horizontal Scaling

• Account Vending - Automated account creation
• OU Structure - Unlimited OUs
• SCP Policies - Flexible policy assignment
• Network Expansion - Transit Gateway attachments

Vertical Scaling

• Resource Limits - AWS service quotas
• Performance - Multi-AZ deployment
• Throughput - Network Firewall capacity
• Storage - S3 unlimited storage

---

High Availability

Multi-AZ Deployment

All critical components deployed across multiple availability zones:

• Network Firewall - Active in multiple AZs
• NAT Gateways - One per AZ
• Transit Gateway - Multi-AZ by default
• S3 Storage - Replicated across AZs

Disaster Recovery

• RTO - Recovery Time Objective: 4 hours
• RPO - Recovery Point Objective: 1 hour
• State Backups - Automated every 6 hours
• Cross-Region - Optional replication

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Related Documentation

• Security Architecture
• Network Architecture
• Zero Trust Implementation
• Disaster Recovery

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For detailed implementation, see the Complete Implementation Guide.