Two Tools That Rarely Compete for the Same Budget Line
Identity as a Service (IDaaS) is a cloud-hosted identity provider: it authenticates users, issues single sign-on sessions, and enforces multi-factor authentication for the applications it’s connected to. Okta, Microsoft Entra ID, and Ping Identity are common examples. IDaaS answers "is this login legitimate, and should it get a session."
An IVIP answers a different question: "what does every identity in this environment actually have access to, right now, including the identities and systems that never went through an IDaaS login flow at all." An IDaaS only has visibility into the applications it federates; it has no native way to see a local account, an on-prem legacy system, or a service account that authenticates without ever touching the IdP.
In practice, an IVIP and an IDaaS aren’t alternatives. An IVIP typically treats the IDaaS as one of the data sources it correlates, feeding it context about identities and access the IDaaS itself has no visibility into, while relying on the IDaaS for the authentication and session-management job it already does well.