CMU Web Login (Shibboleth SAML 2.0 Identity Provider)
Carnegie Mellon's campus-wide single sign-on identity provider, running Shibboleth on CMU's own host and address space (login.cmu.edu, 128.2.42.22). Its SAML 2.0 metadata is publicly readable at the canonical /idp/shibboleth location, and it is a registered InCommon — and thereby eduGAIN — entity carrying the Research & Scholarship entity category, which is a machine-readable commitment to release a defined attribute bundle to R&S service providers. An authentication service for relying service providers, not a data API, and the single most unambiguously institution-operated machine-readable surface CMU publishes.