# Integration architectures
<a name="architectures"></a>

This section discusses individual architectures that you can use to integrate third-party services in the AWS Cloud.

To choose an architecture, these are the most important characteristics to consider:

1. **Direction of traffic** – Unidirectional or bidirectional

1. **Network protocol** – TCP or UDP

1. **Scalability** – Number of virtual private clouds (VPCs) that the third-party service must support

The following figure is a decision chart to help you select an architecture for integrating third-party services in the AWS Cloud.

![Decision tree to select implementation architecture](http://docs.aws.amazon.com/prescriptive-guidance/latest/integrate-third-party-services/images/decision-tree.png)


The following table compares the integration architectures discussed in this guide.


****  

|   | Architecture 1: AWS PrivateLink | Architecture 2: VPC peering | Architecture 3.1: Transit Gateway with AWS RAM | Architecture 3.2: Transit Gateway peering | 
| --- | --- | --- | --- | --- | 
| Routing type | Direct peering | Direct peering | Central hubs with direct peering connections | Central hubs with direct peering connections | 
| Traffic is not exposed to the public internet | Yes | Yes | Yes | Yes | 
| Typical implementation complexity | Low | Low | High | High | 
| Typical architecture complexity | Low | High | Medium | Medium | 
| Support for bidirectional traffic | No | Yes | Yes | Yes | 
| Support for overlapping Classless Inter-Domain Routing (CIDR) blocks | Yes | No | No | No | 
| Support for transitive routing | No | No | Yes | Yes | 
| Support for inter-Region connections | No | Yes | Yes | Yes | 
| Supported traffic types | TCP | TCP and UDP | TCP and UDP | TCP and UDP | 
| Highly scalable | Yes | No | Yes | Yes |