Module mrp 

Message Reliability Protocol (MRP) timing parameters and backoff math per Matter specification section 4.12.

Peers advertise their session intervals in mDNS TXT records (keys SII, SAI, SAT - decimal milliseconds). Senders derive retransmission deadlines from these values using exponential backoff with jitter:

t = i * MARGIN * BASE^max(0, n - THRESHOLD) * (1 + rand * JITTER)

where i is the peer’s active interval (SAI) if the peer was heard from within the active threshold (SAT), otherwise its idle interval (SII), and n is the 0-based retransmission index. A message is given up on after MRP_MAX_TRANSMISSIONS total transmissions.

Used by [crate::retransmit] (handshake exchanges) and [crate::active_connection] (operational traffic). Parameters are stored on the transport connection (crate::transport::ConnectionTrait::mrp_params).

Structs

MrpParameters

Peer MRP intervals, typically taken from its mDNS TXT records.

Constants

MRP_BACKOFF_BASE

MRP_BACKOFF_JITTER

MRP_BACKOFF_MARGIN

MRP_BACKOFF_THRESHOLD

MRP_MAX_INTERVAL_MS

Spec cap for advertised SII/SAI values (milliseconds).

MRP_MAX_TRANSMISSIONS

Maximum number of transmissions of a single message (initial + retransmits).

Functions

backoff_interval

Wait time before the next retransmission per spec 4.12 backoff formula. retransmission_index is 0 for the wait after the initial transmission.

base_interval

Base retransmission interval: the peer’s active interval if it was heard from within the active threshold, otherwise its idle interval.