QoS minimum egress bandwidth support

RFE: https://bugs.launchpad.net/neutron/+bug/1560963

Problem Description

The current QoS API [1] does not provide functionality to define an assured minimum egress bandwidth per port. This proposal talks about enhancing the existing QoS API’s by adding assured minimum egress bandwidth.

This functionality is currently supported in:

  • Open vSwitch: minimum bandwidth assurance is supported, although the traffic shaping applies only to egress traffic, from the switch point of view. This egress traffic (from the switch point of view) should not be mistaken with the egress traffic from the tenant, which is the goal of this new feature.
  • Linux Bridge: using traffic control HTB [2] implementation.
  • SR-IOV: it will depends on the NIC driver and the ip-link [3] version, which needs to have “min_tx_rate” option; this option was merged in version 3.16.0.

Proposed Change

The proposed change is an update to the QoS API and the drivers mentioned (Open vSwitch, Linux Bridge and SR-IOV) to support minimum egress bandwidth assurance. The value of the bandwidth will be stored as an integer value, with valid values greater than zero. The unit is kbps, the same unit used in QosBandwidthLimitRule.

The scope of this feature is to enable the API access to the egress minimum bandwidth value and to enable this feature in the previous commented drivers. This feature doesn’t provide a method to inform about the backend capacity or to check the bandwidth availability. These limitations will be documented in user and developer guides.

Data Model Impact

The model follows the way that the QoS Bandwidth Limiting functionality applies to QoS policies by adding a QosMinimumBandwidthRule table.

The QosMinimumBandwidthRule model would look like:

+--------------+-------+----------+--------+-----------------+------------+
|Attribute     |Type   |Access    |Default |Validation/      |Description |
|Name          |       |          |Value   |Conversion       |            |
+==============+=======+==========+========+=================+============+
|id            |string |RO, all   |generat_|uuid             |identity    |
|              |(UUID) |          |ed      |                 |            |
+--------------+-------+----------+--------+-----------------+------------+
|qos_policy_id |string |RO, all   |N/A     |uuid             |QoSPolicy   |
|              |(UUID) |          |        |                 |reference   |
+--------------+-------+----------+--------+-----------------+------------+
|min_kbps      |integer|RW, tenant|N/A     |not negative,    |Minimum     |
|              |       |          |        |<= max_kbps      |bandwidth   |
+--------------+-------+----------+--------+-----------------+------------+
|direction     |enum   |RW, tenant|'egress'|'egress'         |Traffic     |
|              |       |          |        |                 |direction   |
+--------------+-------+----------+--------+-----------------+------------+

If “max_kbps” is None, the validation check for “min_kbps” will not apply.

This QoS rule can be used in combination with QoS bandwidth limit rule, defined in Neutron QoS API Models and Extension [4].

Both “qos_policy_id” and “direction” will be linked as a unique constraint set, because the combination of both parameters must be unique.

This QoS rule will have a “direction” parameter to define the direction of the traffic. This new feature will implement only egress traffic shaping. “ingress” traffic direction won’t be allowed for the nonce.

REST API Impact

Proposed attribute:

SUB_RESOURCE_ATTRIBUTE_MAP = {
   'minimum_bandwidth_rules':{
        'parent': {'collection_name': 'policies',
                   'member_name': 'policy'},
        'parameters': dict(QOS_RULE_COMMON_FIELDS,
            **{'min_kbps': {
                'allow_post': True, 'allow_put': True,
                'convert_to': attr.convert_to_int,
                'is_visible': True, 'default': None,
                'validate': {'type:non_negative': None,
                             'type:values': max_kbps}}
              }),
            **{'direction': {
                'allow_post': True, 'allow_put': True,
                'is_visible': True, 'default': 'egress',
                'validate': {'type:values': common_constants.
                             EGRESS_DIRECTION}}
              }),
        }
}

Sample REST calls:

GET /v2.0/qos/policies

Response:
{
    "policy": {
        "name": "TypeOne",
        "description": "This policy sets a minimum bandwidth for type one users",
        "shared": "False"
     }
}

GET /v2.0/qos/policies/<policy-uuid>

Response:
{
    "policy": {
        "tenant_id": "<tenant-id>",
        "id": "<id>",
        "name": "TypeOne",
        "description": "This policy sets a minimum bandwidth for type one users",
        "shared": False,
        "rules": [{
            "id": "<id>",
            "policy_id": "<policy-uuid>",
            "rule_type": neutron.services.qos.RULE_TYPE_MINIMUM_BANDWIDTH
            "min_kbps": 10000,
            "direction": "egress"
        }]
     }
}

POST /v2.0/qos/policies/<policy-uuid>/minimum_bandwidth_rules/
{
    "minimum_bandwidth_rule": {
        "min_kbps": 20000,
        "direction": "egress"
    }
}

Response:
{
    "minimum_bandwidth_rule":{
        "id": "<id>",
        "policy_id": "<policy-uuid>",
        "min_kbps": 20000,
        "direction": "egress"
    }
}

PUT /v2.0/qos/policies/<policy-uuid>/minimum_bandwidth_rules/<rule-uuid>
{
    "minimum_bandwidth_rule": {
        "min_kbps": 10000,
        "direction": "egress"
    }
}

Response:
{
    "minimum_bandwidth_rule":{
        "id": "<id>",
        "policy_id": "<policy-uuid>",
        "min_egress_kbps": 10000,
        "direction": "egress"
    }
}

Command Line Client Impact

  • qos-minimum-bandwidth-rule-create <policy-id> –min-kbps <value> –direction <value>
  • qos-minimum-bandwidth-rule-show <rule-id> <policy-id>
  • qos-minimum-bandwidth-rule-list <policy-id>
  • qos-minimum-bandwidth-rule-update <rule-id> <policy-id> –min-kbps <value> –direction <value>
  • qos-minimum-bandwidth-rule-delete <rule-id> <policy-id>

Security Impact

None

Notifications Impact

None

Performance Impact

None

IPv6 Impact

None

Other Deployer Impact

Deployers may need to configure the specific QoS driver / ML2 agent extension.

Developer Impact

None

Community Impact

None

Implementation

Assignee(s)

  • Rodolfo Alonso Hernandez
  • Miguel Angel Ajo
  • Hirofumi Ichihara
  • Moshe Levi

Work Items

  • Versioned DB objects for the new rule type
  • API changes to allow for minimum egress bandwidth modifications
  • Client changes to allow minimum egress bandwidth values being set
  • QoS Openflow integration within the L2 agent extension for the Open vSwitch driver to enable the minimum egress bandwidth support:
    • Added/modified switch flows to mark the packet processing queue.
    • Added/modified QoS rules and processing queues in the integration bridge, physical bridges and tunnel bridge.
  • QoS Traffic Control integration within the L2 agent extension for the Linux Bridge driver to enable this feature.
  • QoS ip-link integration within the L2 agent extension for the SR-IOV driver to enable this feature. Add a sanity check to detect the version of ip-link tool; minimum version required is 3.16.0.

Open vSwitch driver

The current Open vSwitch QoS implementation only shapes egress traffic.

Linux Bridge driver

The current Linux Bridge QoS implementation using Traffic Control (TC) only shapes egress traffic (from the interface point of view). To shape ingress traffic from the interface point of view (egress from the instance), what is needed in this feature, the following steps are required:

  • Create a IFB [5].
  • Send all ingress traffic to this IFB, mirroring it, using a TC rule. This traffic will be sent to this IFB as egress traffic.
  • Add a qdisc and a class in this IFB, with the QoS filter.

Also the algorithm used, TBF [6], must be substituted by HTB [2], a classful algorithm that allows to set a “rate” parameter, defined as the “maximum rate this class and all its children are guaranteed”.

Future work

  • Implement a method to report backend capacity to Neutron. Several methods to enable this feature can be carried out:
    • Use an agent to periodically read the capacity of the backends, using config files, monitoring systems, etc. The agent state reports could be used for that purpose. The information could come from system inspection also enabling an option to override the details in the agent config file. The bandwidth mapping should be per physical network, and there’s a peculiarity we must consider: connection to physical networks can happen by several unbound interfaces (like an SR-IOV card having several PFs (with it’s separate cables) to the switch. That would effectively give different connection resources to the same net which are exhausted separately. This is the best option.
    • Insert the backend capacity manually, using a static file during the deployment process.
    • Enable an API to manually insert the backend capacity. The API can be used for testing and development purposes, but this option should be avoided.
  • Inform Nova Scheduler about the total backend capacity and the QoS minimum egress bandwidth rules, to improve the Scheduler decision. This feature is being addressed by [RFE] Strict minimum bandwidth support (egress) [7].

Dependencies

None

Testing

API-tests

  • Creating minimum egress bandwidth values
  • Updating minimum egress bandwidth values
  • Deleting minimum egress bandwidth values
  • Listing minimum egress bandwidth values
  • Showing a minimum egress bandwidth value

Functional Tests

Functional tests will be used to verify system interactions:

  • Setting minimun egress bandwidth values
  • Updating minimun egress bandwidth values
  • Deleting minimun egress bandwidth values
  • Listing minimun egress bandwidth values

Fullstack Tests

  • Setting a QoS policy for minimum egress bandwidth on the port of the first instance from the API, making a query to the backend and check the correctness of the stored values.
  • Updating QoS policy and checking again the values.
  • Deleting QoS policy and verifying all the values related to the rule are deleted.

These are no benchmark tests.

Documentation Impact

User Documentation

Existing Networking Guide [8] will be updated for this feature.

Existing CLI guide [9] will be updated for this feature.

Developer Documentation

Existing QoS devref document [10] will be updated for this feature.

API Documentation

Existing QoS API documentation [11] will be updated for this feature.