XDPnet This document describes the deprecation of IPv6 extension headers on the Internet with the exception of Encapsulating Security Payload. Deprecation is motivated by three factors: 1) the data shows high discard rates for packets with extension headers sent over the Internet, 2) extension headers can be used for Denial of Service attack and are replete with other security vulnerabilities, 3) the high loss rates are a disincentive to develop new extension headers or options that might be useful or fix known problems. This document recommends that extension headers, other than Encapsulating Security Payload, be relegated to use only in limited domains and that packets with extension headers should be discarded at boundary routers of limited domains.