Multiparty Session Types (MPST) are a typing discipline for communication-centric systems, guaranteeing communication safety, deadlock freedom and protocol compliance. Several works have emerged which model failures and introduce fault-tolerance techniques. However, such works often make assumptions on the underlying network, e.g., TCP-based communication where messages are guaranteed to be delivered; or adopt centralised reliable nodes and an ad-hoc notion of reliability; or address only a single kind of failure, e.g., node crash failures. In this work, we develop MAGπ-a Multiparty, Asynchronous and Generalised π-calculus, which is the first language and type system to accommodate in unison: (i) the widest range of non-Byzantine faults, including message loss, delays and reordering; crash failures and link failures; and network partitioning; (ii) a novel and most general notion of reliability, taking into account the viewpoint of each participant in the protocol; (iii) the spectrum of network assumptions from the lowest UDP-based network programming to the TCP-based application level. We prove subject reduction and session fidelity; process properties, (deadlock freedom, termination); failure-handling safety and reliability adherence.

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Multiparty Session Types (MPST) are a typing discipline for communication-centric systems, guaranteeing communication safety, deadlock freedom and protocol compliance. Several works have emerged which model failures and introduce fault-tolerance techniques. However, such works often make assumptions on the underlying network, e.g., assuming TCP-based communication where messages are guaranteed to be delivered; or adopting centralised reliable nodes and ad-hoc notions of reliability; or only addressing a single kind of failure, such as node crashes. In this work, we develop MAG$$\pi $$ π —a Multiparty, Asynchronous and Generalised $$\pi $$ π -calculus, which is the first language and type system to accommodate in unison: (i) the widest range of non-Byzantine faults, including message loss, delays and reordering; crash and link failures; and network partitioning; (ii) a novel and most general notion of reliability, taking into account the viewpoint of each participant in the protocol; (iii) a spectrum of network assumptions from the lowest UDP-based network programming to the TCP-based application level. We prove subject reduction and session fidelity; process properties (deadlock freedom, termination, etc.); failure-handling safety and reliability adherence.