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The InCommon Federation operates a centralized Federated Error Handling Service that SPs can use to generate simple but effective error pages for the end user. The Service offers a simplified mechanism for obtaining the errorURL value from metadata or delegating the handling of the "missing attribute" error condition if the set of IdPs is a strict subset of InCommon members.
Note that this This Service is deployed on the same production infrastructure that hosts InCommon metadata and the InCommon Discovery Service. All of these services are available 24x7 with manual failover to a redundant hot spare in the event of an outage.
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In the case of Shibboleth Service Provider software, applications or protected scripts have access to the identity provider's entityID via the Shib-Identity-Provider variable/header. Other information in the IdP's metadata, such as the errorURL, user interface extensions, and contact information, are not easily accessible except by parsing the metadata directly. The Federated Error Handling service Service offers a simplified mechanism for obtaining the errorURL value or delegating the handling of the "missing attribute" error condition if the set of IdPs is a strict subset of InCommon membersfrom metadata.