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RFC 8586: Loop Detection in Content Delivery Networks (CDNs)

Stephen Ludin, Mark Nottingham, Nick Sullivan
Internet Engineering Task Force (IETF). 2019.
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This document defines the CDN-Loop request header field for HTTP. CDN-Loop addresses an operational need that occurs when an HTTP request is intentionally forwarded between Content Delivery Networks (CDNs), but is then accidentally or maliciously re-routed back into the original CDN causing a non-terminating loop. The new header field can be used to identify the error and terminate the loop.