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NC-SI ("Network Controller Sideband Interface") is an electrical interface and protocol defined by the Distributed Management Task Force enabling the connection of a Baseboard Management Controller (MC) to a set of Network Interface Controller (NICs) in server computer systems for the purpose of enabling out-of-band remote manageability.

Hardware interface[edit]

The NC-SI interface is based on the RMII interface with some modifications allowing connection of multiple network controllers to a single MC. It contains the following signals:

Signal Description
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 MC)
TX_EN Transmit Enable - Data Valid for traffic sent from the MC
TXD[1:0] Transmit Data (from MC to NC)
RX_ER Receive Error
ARB_IN Hardware Arbitration ring - input
ARB_OUT Hardware Arbitration ring - output

Traffic types[edit]

NC-SI traffic can be either:

  • Pass Through traffic
  • Control traffic

Both types of traffic are Ethernet frames. Pass through traffic consists of data exchanged between the MC 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:

  1. Commands - Commands from the MC to one of the NCs.
  2. Responses - Response of the NC to the command.
  3. AENs (Asynchronous Events Notifications) - Notifications sent asynchronously by the NC. These are equivalent to interrupts.

See also[edit]

External links[edit]