Stratum Chassis Configuration

Chassis config is an internal data structure used by Stratum. The term “chassis” refers to a switching box with one or more switching nodes (e.g., chips). The chassis config file is usually placed on disk and loaded when starting Stratum. This config includes all the not-so-frequent settings that are required before the switch can accept flow programming requests from the controller.

In the following, we provide a non-exhaustive overview of the configurations relevant to SD-Fabric for Tofino-based devices. For a complete reference check out the ChassisConfig Protobuf message format and the guide for running Stratum on Tofino-based switches in the Stratum repository.

Tip

Check out the Stratum repository for examples of chassis config files for different switch platforms.

See the Deployment Guide to learn about how to deploy Stratum with a custom chassis config.

Note

In Stratum the external interface for pushing config is gNMI. The protobuf realization of the YANG models for the config is internally converted to a chassis config before it is consumed by the internal stack components. Not all configurations are available through gNMI, for this reason we recommend using the chassis config file.

The file uses the protobuf text format, check out the protobuf language guide for more info

Chassis

A valid chassis config includes a chassis, a node field, and one or more singleton_port fields.

A chassis uniquely identifies a switch with a single management interface. Each chassis may contain one or more slots (aka linecards), and one or more switching nodes (aka chips) on each slot.

A chassis contains the following fields:

platform: The chassis platform, e.g., PLT_GENERIC_BAREFOOT_TOFINO for Tofino-based devices (check out here for other platforms). Required
name: An arbitrary name for the chassis. Optional
config_params: Parameters for the entire chassis, usually empty for Tofino-based devices. Optional

Node

A node uniquely identifies a single switching node (aka chip) on a chassis linecard and all its flow-related and config-related parameters.

A node contains the following fields:

id: An arbitrary ID of the switch node on the chassis (corresponds to the P4Runtime device ID). Required
name: An arbitrary name for the switching node. Optional
slot: The 1-base index of the slot (aka linecard) to which this node belongs. Required
index: An optional 1-based index of the node within the chassis. Optional

Singleton Port

A singleton port uniquely identifies a switch port and it contains the following fields:

id: An arbitrary ID, unique in the scope of a chassis. Required
Note
We recommend using the following naming convention for both ONOS network config and Stratum chassis config:

For unchannelized ports, use the front panel port number directly.

For channelized ports, use the front panel port number * 100 + channel id. For example, we can use port id 2903 for port 29/3 (port 29 channel 3).

Note that we use zero-based channel number for singleton port id but the channel field described below uses one-based channel number.
name: An optional user friendly name for the port (e.g., 10/1 to identify channel 1 of front-panel port 10). Required

ONOS obtains this name via gNMI and uses it internally to represent ports.
slot: The 1-base index of the slot (aka linecard) of the port. Required
port: The 1-base index of the singleton port on the slot. Required
channel: The 1-base channel index. Absence or zero means non-channelized. Optional
speed_bps: The speed of the port in bps. Required
node: The id of the corresponding node that the port belongs to. Required
config_params: Optional
- admin_state: The initial admin state for this port, disabled by default.
  - Choose from ADMIN_STATE_DISABLED or ADMIN_STATE_ENABLED.
- autoneg: Whether auto-negotiation is enabled or not for this port.
  - Choose from TRI_STATE_FALSE or TRI_STATE_TRUE
  - The initial configuration might be different if this field is empty, based on the platform or the connector you are using.
- fec_mode: Forward Error Correction (FEC) mode
  - Choose from FEC_MODE_ON, FEC_MODE_OFF, or FEC_MODE_AUTO

Example chassis config

In this example, we want to set up a Tofino-based switch with only one node, one slot, and two ports:

Port 1: 100G port without channelization, enabled by default, without auto-negotiation.
Port 2: break out port with four 10G channels, enabled by default, with auto-negotiation.

description: "A chassis config example."
chassis {
    platform: PLT_GENERIC_BAREFOOT_TOFINO
    name: "leaf-1"
}
nodes {
    id: 1
    slot: 1
    index: 1
}
singleton_ports {
    id: 1
    name: "1/0"
    slot: 1
    port: 1
    speed_bps: 100000000000 # 100G
    config_params {
        admin_state: ADMIN_STATE_ENABLED
        autoneg: TRI_STATE_FALSE
    }
    node: 1
}
singleton_ports {
    id: 200
    name: "2/0"
    slot: 1
    port: 2
    channel: 1
    speed_bps: 10000000000 # 10G
    config_params {
        admin_state: ADMIN_STATE_ENABLED
        autoneg: TRI_STATE_TRUE
    }
    node: 1
}
singleton_ports {
    id: 201
    name: "2/1"
    slot: 1
    port: 2
    channel: 2
    speed_bps: 10000000000 # 10G
    config_params {
        admin_state: ADMIN_STATE_ENABLED
        autoneg: TRI_STATE_TRUE
    }
    node: 1
}
singleton_ports {
    id: 202
    name: "2/2"
    slot: 1
    port: 2
    channel: 3
    speed_bps: 10000000000 # 10G
    config_params {
        admin_state: ADMIN_STATE_ENABLED
        autoneg: TRI_STATE_TRUE
    }
    node: 1
}
singleton_ports {
    id: 203
    name: "2/3"
    slot: 1
    port: 2
    channel: 4
    speed_bps: 10000000000 # 10G
    config_params {
        admin_state: ADMIN_STATE_ENABLED
        autoneg: TRI_STATE_TRUE
    }
    node: 1
}