Port data plane status


Neutron may not be well equipped to detect data plane failures affecting the underlying networking infrastructure. This spec addresses that issue by means of allowing external tools to report to Neutron about faults in the underlying data plane that are affecting the ports. A new REST API field is proposed to that end.

Problem Description

An initial description of the problem was introduced in bug #159801 [1]. This spec focuses on capturing one (main) part of the problem there described, i.e. extending Neutron’s REST API to cover the scenario of allowing external tools to report network failures to Neutron. Out of scope of this spec are works to enable port status changes to be received and managed by mechanism drivers.

This spec provides the plumbing to address bug #1575146 [2] in subsequent work. Specifically, and argued by the Neutron driver team in [3]:

  • Neutron should not shut down the port completely upon detection of underlay network failure; connectivity between instances on the same node may still be reachable. External tools may or may not want to trigger a status change on the port based on their own logic and orchestration.

  • Port down is not detected when an uplink of a switch is down.

  • The physical network bridge may have multiple physical interfaces plugged; shutting down the logical port may not be needed when network redundancy is in place.

Use case

The network elements of a cloud infrastucture is managed by two SDN controllers: SDN controller A manages the virtual switches hosted on OpenStack nodes, and SDN controller B manages Top of Rack (ToR) switches.

                   | Orchestrator/ |
       +-----------+  Fault Mmgmt  +---------+
       |           +---------------+         |
       |                                     |
       |                                     |
+------+-------+                       +-----+----+
|     SDN      |                       |  Neutron |
| Controller B |                       +-----+----+
+------+-------+                             |
       |                                     |
       |                                     |
       |                              +------+-------+
 +-----+------+                       |     SDN      |
 | ToR Switch |                       | Controller A |
 +------------+                       +------+-------+
                                        | vSwitch |

SDN Controller B has network monitoring capabilities that enables northbound users to be notified of topology changes, e.g. due to hardware failures or cable pulled. In this use case, user is an orchestrator with fault management capabilities that collects fault events from multiple data sources and updates the status of affected cloud resources. The orchestrator can be a system composed by various OpenStack projects such as Vitrage/Monasca for Root Cause Analysis (RCA), Congress for cloud resource status updates and remediation actions, and Aodh for event alarming.

One possible workflow is:

  1. SDN Controller B detects ToR switch port down and reports to orchestrator;

  2. Orchestrator finds affected cloud resources (e.g. (sub)set of Neutron ports attached to Nova instances) caused by the underlay data plane outage;

  3. Orchestrator updates the data plane port status of those Neutron ports;

  4. Neutron sends notification to the message bus;

  5. Aodh and Congress consume Neutron notifications:

  1. Aodh sends an event alarm to affected Neutron port users;

  2. Congress triggers remediation actions (e.g. Congress policy actions) for switch-over to a standby instance.

A similar workflow was presented at the OpenStack Summit Barcelona keynote demo [4].

Proposed Change

A couple of possible approaches were proposed in [1] (comment #3). This spec proposes tackling the problem via a new extension API to the port resource. The extension adds a new attribute data_plane_status to represent the status of the underlay data plane. This attribute is to be managed by entities outside of Neutron, while the ‘status’ attribute is managed by Neutron. Both status attributes are independent from one another.

The field should be read-only by project users and read-write by any user with a specific role.

Data Model Impact

A new attribute will be added to the ‘ports’ table as a Neutron extension.

Attribute Name



Default Value

Validation/ Conversion



R, project RW, user w/role




A new API extension to the ports resource is going to be introduced.

    'ports': {
        'data_plane_status': {'allow_post': False, 'allow_put': True,
                              'default': None, 'is_visible': True}



Updating port data plane status to down:

PUT /v2.0/ports/<port-uuid>
Accept: application/json
    "port": {
        "data_plane_status": "DOWN"

Command Line Client Impact

openstack port set [--data-plane-status <ACTIVE/DOWN>] <port>

Argument –data-plane-status is optional.