Univ. of Rome Tor Vergata / CNIT Consultant Telefonica, I+D Extensible In-band Processing (EIP) extends the functionality of the IPv6 protocol considering the needs of future Internet services and advanced in-band metadata processing. This document discusses the architecture and framework of EIP. Separate documents respectively analyze a number of use cases for EIP, provide protocol specifications for EIP, and describe the integration of EIP within the IOAM framework through the Global Opaque Block (GOB) of the IOAM Pre-allocated Trace Option.