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|Organization||Distributed Management Task Force (DMTF)|
|Base standards||Platform Management Components Intercommunication (PMCI)|
NC-SI ("Network Controller Sideband Interface") is an electrical interface and protocol defined by the Distributed Management Task Force (DMTF), which enables the connection of a Baseboard Management Controller (BMC) to a set of Network Interface Controller (NICs) in server computer systems for the purpose of enabling out-of-band remote manageability.
The NC-SI interface is based on the RMII interface with some modifications allowing connection of multiple network controllers to a single BMC. It contains the following signals:
|REF_CLK||A 50 MHz clock reference for receive, transmit, and control interface|
|CRS_DV||Carrier Sense/Receive Data Valid for traffic sent from one of the NCs|
|RXD[1:0]||Receive Data (from NC to BMC)|
|TX_EN||Transmit Enable - Data Valid for traffic sent from the BMC|
|TXD[1:0]||Transmit Data (from BMC to NC)|
|ARB_IN||Hardware Arbitration ring - input|
|ARB_OUT||Hardware Arbitration ring - output|
NC-SI traffic can be either pass-through or control traffic, with both traffic types in form of Ethernet frames. Pass-through traffic consists of data exchanged between the BMC and the network via the NC-SI interface. Control traffic includes frames used to configure and control of the NC-SI interface and is identified by an EtherType of 0x88F8.
There are three types of control packets:
- Commands, sent from the BMC to one of the NCs.
- Responses, sent by the NCs as results of the commands.
- AENs (Asynchronous Events Notifications), sent asynchronously by the NCs, equivalent to interrupts.
- Management Component Transport Protocol (MCTP)
- Platform Management Components Intercommunication (PMCI)