NC-SI
NC-SI ("Network Controller Sideband Interface") is an electrical interface and protocol defined by the Distributed Management Task Force (DMTF). NC-SI enables the connection of a Management Controller (MC), also known as a Baseboard Management Controller (BMC) to one or more Network Controllers (NCs) or Network Interface Controller (NICs) in server computer systems for the purpose of enabling out-of-band manageability. It allows the BMC to share the network connections of the NIC ports for management traffic and the host traffic. The NC-SI defines a control communication protocol between the BMC and NICs. The NC-SI is supported over several transports and physical interfaces.
| Status | Published |
|---|---|
| Year started | 2010 |
| Organization | Distributed Management Task Force (DMTF) |
| Base standards | Platform Management Components Intercommunication (PMCI) |
| Domain | Out-of-band management |
| Abbreviation | NC-SI |
| Website | www |
Hardware interface
The RBT (RMII-Based Transport) interface defined by NC-SI is based on the RMII specification with some modifications allowing connection of multiple network controllers to a single BMC. NC-SI can also operate over a variety of other electrical interfaces including SMBus and PCIe when used over the Management Component Transport Protocol (MCTP).
RBT is made up of 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 BMC |
| TXD[1:0] | Transmit Data (from MC to NC) |
| RX_ER | Receive Error signal sent from the NC to the MC (optional) |
| ARB_IN | Hardware Arbitration ring - input (optional) |
| ARB_OUT | Hardware Arbitration ring - output (optional) |
Traffic types
NC-SI defines two fundamental types of traffic, pass-through and control traffic. Pass-through traffic consists of data exchanged between the BMC and the network via the NC-SI interface. Control traffic is used to inventory and configure aspects of NIC operation and control the NC-SI interface.
Control traffic is broken down into three sub-types:
- Commands, sent from the BMC to one of the NCs.
- Responses, sent by the NCs as results of the commands.
- AENs (Asynchronous Event Notifications), sent asynchronously by the NCs, equivalent to interrupts, upon the occurrence of the specified event.
When NC-SI is used over RBT, standard Ethernet framing is used for all traffic types. Control traffic is identified by using an EtherTypeof 0x88F8. When NC-SI is used in conjunction with MCTP, MCTP provides the packetization methodology and traffic type identification.
See also
- Management Component Transport Protocol (MCTP)
- Platform Management Components Intercommunication (PMCI)