Transit Gateway v/s Direct Connect v/s Site-to-Site VPN

Let’s discuss about VPC today, we all must have heard of Transit gateway, Direct Connect and Site-to-Site VPN, all of these seem to sound similar, but what’s the difference between them?

A 𝗧𝗿𝗮𝗻𝘀𝗶𝘁 𝗚𝗮𝘁𝗲𝘄𝗮𝘆 is a central hub by which you can connect VPCs and on-premises networks within the AWS environment.
𝗗𝗶𝗿𝗲𝗰𝘁 𝗖𝗼𝗻𝗻𝗲𝗰𝘁 does this by creating a direct, dedicated private connection with your on-premises network and AWS.
Creating a 𝗦𝗶𝘁𝗲-𝘁𝗼-𝗦𝗶𝘁𝗲 𝗩𝗣𝗡 creates an encrypted over-the-public-internet “tunnel” to associate your on-premises network with a single AWS VPC.
So, in fact, a Transit Gateway provides for managing multiple VPCs and on-premises networks connections, with Direct Connect offering a direct, high-bandwidth connection, and a Site-to-Site VPN is a fundamental connection using the public Internet for a single VPC link.

𝗞𝗲𝘆 𝗱𝗶𝗳𝗳𝗲𝗿𝗲𝗻𝗰𝗲𝘀:

𝗙𝘂𝗻𝗰𝘁𝗶𝗼𝗻𝗮𝗹𝗶𝘁𝘆:
𝗧𝗿𝗮𝗻𝘀𝗶𝘁 𝗚𝗮𝘁𝗲𝘄𝗮𝘆 : It is central to make the different VPCs and on-premises network connect to each other; it simplifies network management.
𝗗𝗶𝗿𝗲𝗰𝘁 𝗖𝗼𝗻𝗻𝗲𝗰𝘁 : Dedicated and private connection that connects your on-premises network to AWS with high bandwidth with minimal latency.
𝗦𝗶𝘁𝗲-𝘁𝗼-𝗦𝗶𝘁𝗲 𝗩𝗣𝗡 : An encrypted tunnel across the public internet which interconnects your on-premises network to an AWS VPC.

𝗦𝗰𝗮𝗹𝗮𝗯𝗶𝗹𝗶𝘁𝘆
𝗧𝗿𝗮𝗻𝘀𝗶𝘁 𝗚𝗮𝘁𝗲𝘄𝗮𝘆: It is highly scalable, thus allowing easy addition of new VPCs or on-premises network connections.
𝗗𝗶𝗿𝗲𝗰𝘁 𝗖𝗼𝗻𝗻𝗲𝗰𝘁: Highly scalable depending on the chosen bandwidth tier.
𝗦𝗶𝘁𝗲-𝘁𝗼-𝗦𝗶𝘁𝗲 𝗩𝗣𝗡: Not as scalable as Direct Connect because it is restrained by public internet bandwidth.

𝗦𝗲𝗰𝘂𝗿𝗶𝘁𝘆:
𝗧𝗿𝗮𝗻𝘀𝗶𝘁 𝗚𝗮𝘁𝗲𝘄𝗮𝘆: It is secure in the AWS infrastructure, but on the on-premises connection, there would rely on extra security measures.
𝗗𝗶𝗿𝗲𝗰𝘁 𝗖𝗼𝗻𝗻𝗲𝗰𝘁: Very secure since it is based on a dedicated private connection.
𝗦𝗶𝘁𝗲-𝘁𝗼-𝗦𝗶𝘁𝗲 𝗩𝗣𝗡: Relies on encryption to protect traffic across the internet.

𝗪𝗵𝗲𝗻 𝘁𝗼 𝘂𝘀𝗲 𝗲𝗮𝗰𝗵:
𝗧𝗿𝗮𝗻𝘀𝗶𝘁 𝗚𝗮𝘁𝗲𝘄𝗮𝘆:
You want to connect multiple VPCs and on-premises networks with complex routing requirements.
𝗗𝗶𝗿𝗲𝗰𝘁 𝗖𝗼𝗻𝗻𝗲𝗰𝘁:
You want a high-bandwidth, dedicated private connection to AWS for large data transfers.
𝗦𝗶𝘁𝗲-𝘁𝗼-𝗦𝗶𝘁𝗲 𝗩𝗣𝗡:
You want a simple way to connect a single on-premises network to an AWS VPC with smaller data volumes.