This topic describes the terms commonly used in Express Connect.

The following figure shows the network topology for using physical connections to connect on-premises data centers to Alibaba Cloud.

Note Alibaba Cloud provides multiple physical connection solutions. For more information, see Physical connection solutions.

The following table describes basic terms of physical connections.

Term Description
Express Connect An Alibaba Cloud service that helps you build private network communication channels between VPCs or between VPCs and data centers. It provides better flexibility for your network topology and enhances the performance and security of cross-network communication.
Virtual Private Cloud (VPC) A custom private network created on Alibaba Cloud. VPCs are logically isolated from each other. You can create and manage your cloud instances, such as Elastic Compute Service (ECS) instances, ApsaraDB instances, and Server Load Balancer (SLB) instances in your VPC.
Virtual Border Router (VBR) A router between the customer-premises equipment (CPE) and a VPC. It serves as a bridge for data exchange between your data center and the VPC.
VRouter A hub that connects all vSwitches in a VPC and serves as a gateway to connect the VPC with other networks.
Cloud Enterprise Network (CEN) A network that helps you build private network communication channels between VPCs or between VPCs and data centers. It features automatic route distribution and learning, faster convergence, and improved quality and security of cross-network communication. CEN allows you to connect all your network resources to build a network with enterprise-level communication capabilities.

By using CEN, you do not need to configure routes for VPCs, which simplifies network operation and maintenance. For more information, see What is CEN?.

Physical connection interface A physical interface that is used by a leased line to access an Alibaba Cloud access point.
Access point A geographical location where a physical connection is connected to Alibaba Cloud. Two access devices are deployed in each access point. Each region has one or more access points to enable communication between local data centers and VPCs.
Border Gateway Protocol (BGP) A routing protocol designed to exchange routing and reachability information among gateways, Internet, or autonomous systems.
Equal-cost multi-path (ECMP) link aggregation A mechanism that is used to increase the bandwidth of physical connections by using ECMP routing, or in other words, by connecting multiple leased lines to the same device and associating multiple physical connections with the same VBR.
Exclusive physical connection A physical connection that uses a physical port and requires a physical leased line of a third-party service provider to connect a data center to an Alibaba Cloud access point.
Shared physical connection A physical connection solution where uses a physical connection and the network provided by a third-party service provider to connect an on-premises data center to Alibaba Cloud. In this solution, the third-party service provider establishes the link between their access point and an Alibaba Cloud access point that can be shared by multiple tenants.