Scalable MCTP infrastructure

Methods and apparatus for scalable MCTP infrastructure. A system is split into independent MCTP domains, wherein each MCTP domain uses Endpoint Identifiers (EIDs) for endpoint devices within the MCTP domain in a manner similar to conventional MCTP operations. A new class of MCTP devices (referred to as a Domain Controllers) is provided to enable inter-domain communication and communication with global devices. Global traffic originators or receivers like a BMC (Baseboard Management Controller), Infrastructure Processing Unit (IPU), Smart NIC (Network Interface Card), Debugger, or PROT (Platform Root or Trust) discover and establish two-way communication through the Domain Controllers to any of the devices in the target domain(s). The Domain Controllers are configured to implement tunneled connections between global devices and domain endpoint devices. The tunneled connections may employ encapsulated messages with outer and inner headers and/or augmented MCTP messages with repurposed fields used to store source and destination EIDs.