# Specification of the AUTOSAR Network Management Protocol
###### tags: `專題`
## Introduction
* First, this is a hardware independent protocol.
* Main purpose is to coordinate one or more groups of ECUs to wake up and shutdown their communication stack synchronously.
* The NM algorithm is based on periodic NM message.
* Limitation:
* One NM instance is associated with only one NM cluster in one network. One NM cluster can have only one instance of Nm in one node.
* The maximum size of the NM message is limited by the used communication bus.
* NM algorithm uses services of the underlying communication stack modules to send and receive NM messages.

## Specification
* User Data is considered all data not being part of CBV and NID.
* Partial Network
* [PRS_Nm_00406]{DRAFT} It shall be possible to enable or disable the handling of synchronized PNC shutdown (handling is optional). If handling is enabled, then also PN support shall be enabled.(RS_Nm_00150, RS_Nm_02531)
* [PRS_Nm_00335] Nodes participating in the communication of partial networking shall be pre-configured with the offset and range (in bytes) of the Partial Network Information within the NM message.(RS_Nm_02520)
* Every bit (PN bit) of the PN Info Range represents one Partial Network
* Handling of Rx NM messages
* Handling of Tx NM messages
* Timing behavior
* If communication on the bus is needed i.e. requested, NM messages are sent out. If no communication is needed i.e. released, sending of NM messages is stopped.
* When the “Repeat Message” state is entered because of network request or repeat message request and configured number of immediate NM transmissions is greater than zero (see NmImmediateNmTransmissions), these immediate NM messages shall be transmitted using Immediate NM Cycle Time.
* When a NM node does not need the communication on a bus, it will not immediately shut down.
* CAN NM and UDP NM introduce Prepare Bus Sleep Mode to ensure that all nodes have time to stop their network activity before the Bus Sleep state is entered.
* The FlexRay NM shall be able to separately transmit NM-Data and NM-Vote, or to combine them within one NM message (in either static or dynamic slot). Transmission format shall be configurable (Schedule Variant).
* Each ECU, which participates in the FlexRay NM, is synchronized to a global timebased on periodic repetition of the FlexRay communication cycle.
* Ready Sleep Time is defined as the time that starts when a new repetition cycle starts after bus communication has been released and ends NmReadySleepCnt+1 repetition cycles without any NM-Vote