Network Segmentation Strategies & Traffic Control

Network segmentation is a key security principle that isolates workloads to protect sensitive data, reduce the attack surface, and control traffic flow within an AWS environment.

SecureCart implements network segmentation to: ✔ Prevent lateral movement of threats ✔ Restrict communication between services based on least privilege ✔ Optimize network performance by reducing unnecessary traffic ✔ Enhance compliance and security visibility

This guide covers: ✔ Core network segmentation strategies ✔ Best practices for workload isolation ✔ Use cases for SecureCart’s e-commerce platform

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Core Network Segmentation Strategies

Network segmentation in AWS is achieved using subnet isolation, VPC peering, Transit Gateway, and private networking.

Segmentation Strategy	Description	Use Case in SecureCart
Public vs. Private Subnets	Divides workloads into public (internet-facing) and private (internal-only) subnets.	ALB in public subnets, ECS and RDS in private subnets.
Multi-Tier Segmentation	Separates web, application, and database layers into different subnets for security and performance.	SecureCart’s frontend (ALB), backend (ECS), and database (RDS) exist in isolated tiers.
VPC Peering	Connects two VPCs privately without using the internet.	SecureCart’s payment processing service is in a separate VPC but securely peered with the application VPC.
AWS Transit Gateway	Acts as a centralized router for multi-VPC environments, avoiding multiple peering connections.	SecureCart uses Transit Gateway to connect Dev, Staging, and Production VPCs in different AWS accounts.
AWS PrivateLink	Enables private connectivity to AWS services and third-party APIs without using the internet.	SecureCart connects its payment gateway provider using PrivateLink to avoid public exposure.

Best Practices ✔ Minimize public-facing resources – Only expose what is necessary. ✔ Segment workloads by function – Use separate subnets for web, application, and database layers. ✔ Use private networking whenever possible – Prefer PrivateLink, VPC Peering, and VPC Endpoints.

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Designing Secure Subnet Segmentation

SecureCart divides its network into multiple subnets based on workload function.

A. Public vs. Private Subnets

✔ Public Subnet: Used for internet-facing resources (e.g., ALB). ✔ Private Subnet: Used for internal-only workloads (e.g., ECS, RDS).

Component	Subnet Placement	Access Control
Application Load Balancer (ALB)	Public Subnet	Exposes SecureCart’s frontend to the internet.
ECS Services (Backend API)	Private Subnet	Only accessible by ALB.
RDS Database	Private Subnet	Only accessible by ECS backend (no direct internet access).

Best Practices: ✔ Never place databases in public subnets. ✔ Restrict ALB access to only necessary ports (443, 80). ✔ Use Security Groups to control internal communication.

Multi-VPC Network Segmentation Strategies

Using VPC Peering for Secure Inter-VPC Communication

✔ Connects two VPCs privately without the internet. ✔ Low-latency, direct network connection between VPCs.

🔹 Use Case: SecureCart peers its main application VPC with a separate payment processing VPC for added isolation.

✅ Best Practices: ✔ Peering only when required – Avoid unnecessary complexity. ✔ Use private DNS resolution for inter-VPC communication.

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Using AWS Transit Gateway for Centralized Multi-VPC Routing

✔ Acts as a centralized router to simplify multi-VPC networking. ✔ More scalable than VPC Peering (avoids complex many-to-many peering).

🔹 Use Case:

• SecureCart connects multiple accounts (Dev, Staging, Production) using AWS Transit Gateway.

✅ Best Practices: ✔ Use Transit Gateway over VPC Peering for large-scale architectures. ✔ Apply route table segmentation to prevent unwanted cross-VPC traffic.

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Securing External Connectivity

SecureCart ensures private, secure access to AWS services and third-party providers.

AWS PrivateLink (Secure API Access)

✔ Allows SecureCart to connect to third-party services privately without using the internet.

🔹 Use Case:

• SecureCart connects its payment gateway via PrivateLink to ensure transactions occur over a private connection.

✅ Best Practices: ✔ Use PrivateLink over public API endpoints. ✔ Restrict PrivateLink access using Security Groups & IAM policies.

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B. AWS Direct Connect (On-Premises Integration)

✔ Provides a dedicated private network to on-premises environments.

🔹 Use Case:

• SecureCart uses Direct Connect to securely transfer bulk order data to a third-party logistics provider.

✅ Best Practices: ✔ Encrypt Direct Connect traffic using VPN for additional security. ✔ Monitor Direct Connect link utilization to optimize bandwidth.

Scenario:

SecureCart’s AWS environment must be segmented into public and private subnets to protect backend services from direct internet access.

Key Learning Objectives:

✅ Implement public and private subnet architectures ✅ Configure NAT Gateways & Internet Gateways for controlled access ✅ Set up VPC Peering & Transit Gateway for secure multi-VPC communication ✅ Implement network segmentation for microservices security

Hands-on Labs:

1️⃣ Create Public & Private Subnets in a Multi-AZ VPC 2️⃣ Configure NAT Gateway for Private Subnet Internet Access 3️⃣ Establish VPC Peering Between SecureCart’s Workloads

🔹 Outcome: SecureCart prevents direct access to sensitive workloads while ensuring controlled traffic flows.

Network segmentation is a fundamental security practice that isolates workloads, restricts unauthorized access, and improves performance by managing how traffic flows within an AWS environment.

✔ Why does SecureCart use network segmentation?

• Minimizes attack surface – Prevents lateral movement of threats.

• Enhances security – Ensures workloads only communicate where necessary.

• Optimizes performance – Reduces congestion by segmenting traffic.

• Ensures compliance – Helps meet regulatory and security requirements.

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Key Network Segmentation Strategies in AWS

Segmentation Strategy	Description	Use Case in SecureCart
Public vs. Private Subnets	Segregates workloads into public (internet-facing) and private (internal-only) subnets.	ALB in public subnets, ECS services and RDS database in private subnets.
Multi-Tier Architecture	Separates web, application, and database layers into different subnets.	SecureCart’s frontend (ALB), backend (ECS), and database (RDS) are in isolated network tiers.
VPC Peering	Allows secure communication between two VPCs without using the internet.	SecureCart’s payment processing service is in a separate VPC but securely peered with the main application VPC.
AWS Transit Gateway	Centralized routing for multi-VPC environments.	SecureCart connects multiple AWS accounts securely with a single routing hub.
VPC Endpoints	Enables private access to AWS services (S3, DynamoDB) without using an internet gateway.	SecureCart accesses S3 securely via VPC Endpoints, preventing public exposure.

✅ Best Practice: Reduce public exposure and use private networking whenever possible.

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🔹 Step 2: Designing a Secure VPC Architecture

SecureCart’s network is divided into logical zones based on security needs.

🔹 Public vs. Private Subnet Design

✔ Public Subnets – Only contains ALB (internet-facing). ✔ Private Subnets – ECS tasks, databases, and sensitive services cannot be accessed directly from the internet.

Component	Location	Access Control
Application Load Balancer (ALB)	Public Subnet	Accepts public traffic, forwards to ECS.
ECS Services	Private Subnet	Only ALB can communicate with ECS tasks.
RDS Database	Private Subnet	Only accessible by ECS (via Security Group).

✅ Best Practice: Use private subnets for backend services and databases.

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🔹 Step 3: Controlling Traffic Flow Between Segments

A. Route Tables & Traffic Flow

✔ SecureCart uses custom route tables to control communication between public/private subnets and external networks.

Destination	Target	Purpose
0.0.0.0/0	Internet Gateway	Public internet access (ALB only).
10.0.0.0/16	Local VPC	Internal communication within VPC.
S3 CIDR	VPC Endpoint	Private access to AWS S3.

✅ Best Practice: Avoid unrestricted routes to the internet.