Frame Relay is a legacy packet-switched WAN technology that connected remote sites through a service-provider cloud. It was widely used before MPLS VPNs, Ethernet WAN services, SD-WAN, and internet-based VPNs became common.
How Frame Relay Worked
A customer router connected to a provider Frame Relay network through an access circuit. The provider delivered traffic over logical connections called virtual circuits, allowing several customer sites to share a single physical interface.
Key Frame Relay Terms
- DLCI: a data-link connection identifier used to identify a virtual circuit locally.
- PVC: a permanent virtual circuit that remained provisioned between sites.
- LMI: local management interface messages used to report circuit status.
- CIR: committed information rate, the agreed level of bandwidth.
- FECN and BECN: congestion notifications sent in forward or backward directions.
Why Frame Relay Was Popular
Frame Relay cost less than dedicated point-to-point circuits and gave organizations flexible any-to-any WAN connectivity. It used variable-length frames and relied largely on higher-layer protocols for recovery from errors.
Frame Relay Today
Frame Relay is now considered legacy technology. It may still appear in older certifications, labs, migration projects, and historical network documentation, but new deployments usually use MPLS, Ethernet services, SD-WAN, or secure VPN connections.
Frame Relay vs. Modern WAN Options
- MPLS VPN: scalable provider WAN with traffic separation and QoS options.
- Internet VPN: encrypted connectivity over broadband or fiber.
- SD-WAN: policy-based path selection across multiple links and cloud-managed operations.
- Ethernet WAN: high-bandwidth Layer 2 connectivity between locations.
Continue Learning
Compare this legacy technology with our WAN Technologies guide and MPLS guide. For Cisco study resources, explore the Cisco Premium PDF collection.