ADFS (Active Directory Federation Services)

Active Directory Federation Services (ADFS) is a Microsoft Windows Server role that enables federated identity and single sign-on (SSO) across organizational or domain boundaries. It authenticates users via Active Directory Domain Services (AD DS) and issues claims-based security tokens that trusted applications or partners can use for access, eliminating the need for repeated logins.

Key Capabilities

• Leverages existing Active Directory infrastructure: No need to replicate user stores.

• Single Sign-On (SSO) across boundaries: Users get seamless experience across trusted applications.

• Claims-based model: Flexible, extensible identity information via claims.

• Interoperability: Works with standard federation protocols (SAML, WS-Federation, OAuth / OIDC).

• Controlled security: Token signing, trust boundaries, and proxy layers help secure external access.

Limitations

• Complexity & maintenance overhead: Deployment, proxy infrastructure, certificate management, high availability setups require significant expertise.

• Cost (in practice): Even though ADFS is a Windows Server role (no extra license cost for the role), hardware, RDP, SSL certificates, load balancing, high availability, and operational support add cost.

• Not cloud-native / agility limitations: Modern cloud IAM platforms can offer faster iteration, better native integrations, and features (e.g. adaptive risk, built-in MFA, identity analytics) more easily.

• Scalability & reliability demands: To ensure availability and latency, you often need redundancy, load balancers, proxies, and careful network configuration.

• Upkeep & patching burden: On-prem infrastructure must be updated, secured, monitored, and hardened.

• Less seamless across diverse identity systems: For non-Windows, non-AD systems (e.g. external user bases, hybrid identity), bridging and mapping can get complex.