AWS Transit Gateway Overview

AWS Transit Gateway simplifies network management by allowing a single gateway to connect multiple VPCs, on-premises data centers, and remote networks via VPN and Direct Connect, thereby streamlining network topology in AWS. This technology addresses the complexity of managing extensive network topologies and enables a hub-and-spoke model for efficient connectivity.

Key Features:

• Transitive Peering: Connects thousands of VPCs, on-premises data centers, and remote networks without needing to establish individual peering connections between each network.
• Simplified Connectivity: Through the Transit Gateway, VPCs can communicate with each other, and with on-premises data centers via Direct Connect and VPN connections in a hub-and-spoke architecture.
• Regional Resource & Cross-Region Support: Operates regionally but can work across regions and can be shared across AWS accounts using the Resource Access Manager.
• Route Tables Management: Allows for the creation of route tables to control traffic flow between connected networks, enhancing network security.

Use Cases:

1. Solving Complex Network Topologies: Simplifies the connection of multiple VPCs and on-premises networks by providing a central hub for managing network traffic.
2. IP Multicast Support: The only AWS service that supports IP multicast, crucial for certain network and application architectures.
3. Enhancing VPN Bandwidth with ECMP: Equal-Cost Multi-Path (ECMP) routing can be used to increase the bandwidth of site-to-site VPN connections by allowing traffic to be split across multiple best paths.

Technical Deep Dive:

• Site-to-Site VPN & ECMP: A single site-to-site VPN connection can use ECMP to utilize multiple paths, enhancing throughput beyond the limitations of connecting directly to a VPC. For example, connecting via a Transit Gateway can increase throughput from 1.5 Gbps to 2.5 Gbps and further increase by adding more VPN connections.
• Direct Connect Sharing: Transit Gateway facilitates the sharing of Direct Connect connections across multiple AWS accounts and VPCs, offering a more efficient and cost-effective solution for organizations with complex network requirements.

Cost Considerations: