Quality of Service (QoS)

Quality of Service (QoS)

QoS is defined as the ability to guarantee certain network requirements like bandwidth, latency, jitter, and reliability in order to satisfy a Service Level Agreement (SLA) between an application provider and end users.

Network devices such as switches and routers can mark traffic so that it is handled with a higher priority to fulfill the QoS conditions agreed under the SLA. In other cases, certain network traffic such as Voice over IP (VoIP) and video streaming needs to be transmitted with minimal bandwidth constraints. On a system without network QoS management, all traffic will be transmitted in a “best-effort” manner making it impossible to guarantee service delivery to customers.

QoS is an advanced service plug-in. QoS is decoupled from the rest of the OpenStack Networking code on multiple levels and it is available through the ml2 extension driver.

Details about the DB models, API extension, and use cases are out of the scope of this guide but can be found in the Neutron QoS specification.

Supported QoS rule types

QoS supported rule types are now available as VALID_RULE_TYPES in QoS rule types:

  • bandwidth_limit: Bandwidth limitations on networks, ports or floating IPs.
  • dscp_marking: Marking network traffic with a DSCP value.
  • minimum_bandwidth: Minimum bandwidth constraints on certain types of traffic.

Any QoS driver can claim support for some QoS rule types by providing a driver property called supported_rules, the QoS driver manager will recalculate rule types dynamically that the QoS driver supports.

The following table shows the Networking back ends, QoS supported rules, and traffic directions (from the VM point of view).

Networking back ends, supported rules, and traffic direction
Rule \ back end Open vSwitch SR-IOV Linux bridge
Bandwidth limit Egress \ Ingress Egress (1) Egress \ Ingress
Minimum bandwidth
Egress
DSCP marking Egress
Egress

Note

  1. Max burst parameter is skipped because it is not supported by the IP tool.

In the most simple case, the property can be represented by a simple Python list defined on the class.

For an ml2 plug-in, the list of supported QoS rule types and parameters is defined as a common subset of rules supported by all active mechanism drivers. A QoS rule is always attached to a QoS policy. When a rule is created or updated:

  • The QoS plug-in will check if this rule and parameters are supported by any active mechanism driver if the QoS policy is not attached to any port or network.
  • The QoS plug-in will check if this rule and parameters are supported by the mechanism drivers managing those ports if the QoS policy is attached to any port or network.

Configuration

To enable the service on a cloud with the architecture described in Networking architecture, follow the steps below:

On the controller nodes:

  1. Add the QoS service to the service_plugins setting in /etc/neutron/neutron.conf. For example:

    service_plugins = \
    neutron.services.l3_router.l3_router_plugin.L3RouterPlugin,
    neutron.services.metering.metering_plugin.MeteringPlugin,
    neutron.services.qos.qos_plugin.QoSPlugin
    
  2. Optionally, set the needed notification_drivers in the [qos] section in /etc/neutron/neutron.conf (message_queue is the default).

  3. Optionally, in order to enable the floating IP QoS extension qos-fip, set the service_plugins option in /etc/neutron/neutron.conf to include both router and qos. For example:

    service_plugins = router, qos
    
  4. In /etc/neutron/plugins/ml2/ml2_conf.ini, add qos to extension_drivers in the [ml2] section. For example:

    [ml2]
    extension_drivers = port_security, qos
    
  5. Edit the configuration file for the agent you are using and set the extensions to include qos in the [agent] section of the configuration file. The agent configuration file will reside in /etc/neutron/plugins/ml2/<agent_name>_agent.ini where agent_name is the name of the agent being used (for example openvswitch). For example:

    [agent]
    extensions = qos
    

On the network and compute nodes:

  1. Edit the configuration file for the agent you are using and set the extensions to include qos in the [agent] section of the configuration file. The agent configuration file will reside in /etc/neutron/plugins/ml2/<agent_name>_agent.ini where agent_name is the name of the agent being used (for example openvswitch). For example:

    [agent]
    extensions = qos
    
  2. Optionally, in order to enable QoS for floating IPs, set the extensions option in the [agent] section of /etc/neutron/l3_agent.ini to include fip_qos. If dvr is enabled, this has to be done for all the L3 agents. For example:

    [agent]
    extensions = fip_qos
    
  3. As rate limit doesn’t work on Open vSwitch’s internal ports, optionally, as a workaround, to make QoS bandwidth limit work on router’s gateway ports, set ovs_use_veth to True in DEFAULT section in /etc/neutron/l3_agent.ini

[DEFAULT]
ovs_use_veth = True

Note

QoS currently works with ml2 only (SR-IOV, Open vSwitch, and linuxbridge are drivers enabled for QoS).

DSCP marking on outer header for overlay networks

When using overlay networks (e.g., VxLAN), the DSCP marking rule only applies to the inner header, and during encapsulation, the DSCP mark is not automatically copied to the outer header.

  1. In order to set the DSCP value of the outer header, modify the dscp configuration option in /etc/neutron/plugins/ml2/<agent_name>_agent.ini where <agent_name> is the name of the agent being used (e.g., openvswitch):

    [agent]
    dscp = 8
    
  2. In order to copy the DSCP field of the inner header to the outer header, change the dscp_inherit configuration option to true in /etc/neutron/plugins/ml2/<agent_name>_agent.ini where <agent_name> is the name of the agent being used (e.g., openvswitch):

    [agent]
    dscp_inherit = true
    

    If the dscp_inherit option is set to true, the previous dscp option is overwritten.

Trusted projects policy.json configuration

If projects are trusted to administrate their own QoS policies in your cloud, neutron’s file policy.json can be modified to allow this.

Modify /etc/neutron/policy.json policy entries as follows:

"get_policy": "rule:regular_user",
"create_policy": "rule:regular_user",
"update_policy": "rule:regular_user",
"delete_policy": "rule:regular_user",
"get_rule_type": "rule:regular_user",

To enable bandwidth limit rule:

"get_policy_bandwidth_limit_rule": "rule:regular_user",
"create_policy_bandwidth_limit_rule": "rule:regular_user",
"delete_policy_bandwidth_limit_rule": "rule:regular_user",
"update_policy_bandwidth_limit_rule": "rule:regular_user",

To enable DSCP marking rule:

"get_policy_dscp_marking_rule": "rule:regular_user",
"create_dscp_marking_rule": "rule:regular_user",
"delete_dscp_marking_rule": "rule:regular_user",
"update_dscp_marking_rule": "rule:regular_user",

To enable minimum bandwidth rule:

"get_policy_minimum_bandwidth_rule": "rule:regular_user",
"create_policy_minimum_bandwidth_rule": "rule:regular_user",
"delete_policy_minimum_bandwidth_rule": "rule:regular_user",
"update_policy_minimum_bandwidth_rule": "rule:regular_user",

User workflow

QoS policies are only created by admins with the default policy.json. Therefore, you should have the cloud operator set them up on behalf of the cloud projects.

If projects are trusted to create their own policies, check the trusted projects policy.json configuration section.

First, create a QoS policy and its bandwidth limit rule:

$ openstack network qos policy create bw-limiter
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| description       |                                      |
| id                | 5df855e9-a833-49a3-9c82-c0839a5f103f |
| is_default        | False                                |
| name              | bw-limiter                           |
| project_id        | 4db7c1ed114a4a7fb0f077148155c500     |
| rules             | []                                   |
| shared            | False                                |
+-------------------+--------------------------------------+


$ openstack network qos rule create --type bandwidth-limit --max-kbps 3000 \
    --max-burst-kbits 2400 --egress bw-limiter
+----------------+--------------------------------------+
| Field          | Value                                |
+----------------+--------------------------------------+
| direction      | egress                               |
| id             | 92ceb52f-170f-49d0-9528-976e2fee2d6f |
| max_burst_kbps | 2400                                 |
| max_kbps       | 3000                                 |
| name           | None                                 |
| project_id     |                                      |
+----------------+--------------------------------------+

Note

The QoS implementation requires a burst value to ensure proper behavior of bandwidth limit rules in the Open vSwitch and Linux bridge agents. If you do not provide a value, it defaults to 80% of the bandwidth limit which works for typical TCP traffic.

Second, associate the created policy with an existing neutron port. In order to do this, user extracts the port id to be associated to the already created policy. In the next example, we will assign the bw-limiter policy to the VM with IP address 192.0.2.1.

$ openstack port list
+--------------------------------------+-----------------------------------+
| ID                                   | Fixed IP Addresses                |
+--------------------------------------+-----------------------------------+
| 0271d1d9-1b16-4410-bd74-82cdf6dcb5b3 | { ... , "ip_address": "192.0.2.1"}|
| 88101e57-76fa-4d12-b0e0-4fc7634b874a | { ... , "ip_address": "192.0.2.3"}|
| e04aab6a-5c6c-4bd9-a600-33333551a668 | { ... , "ip_address": "192.0.2.2"}|
+--------------------------------------+-----------------------------------+

$ openstack port set --qos-policy bw-limiter \
    88101e57-76fa-4d12-b0e0-4fc7634b874a

In order to detach a port from the QoS policy, simply update again the port configuration.

$ openstack port unset --qos-policy 88101e57-76fa-4d12-b0e0-4fc7634b874a

Ports can be created with a policy attached to them too.

$ openstack port create --qos-policy bw-limiter --network private port1
+-----------------------+--------------------------------------------------+
| Field                 | Value                                            |
+-----------------------+--------------------------------------------------+
| admin_state_up        | UP                                               |
| allowed_address_pairs |                                                  |
| binding_host_id       |                                                  |
| binding_profile       |                                                  |
| binding_vif_details   |                                                  |
| binding_vif_type      | unbound                                          |
| binding_vnic_type     | normal                                           |
| created_at            | 2017-05-15T08:43:00Z                             |
| data_plane_status     | None                                             |
| description           |                                                  |
| device_id             |                                                  |
| device_owner          |                                                  |
| dns_assignment        | None                                             |
| dns_name              | None                                             |
| extra_dhcp_opts       |                                                  |
| fixed_ips             | ip_address='10.0.10.4', subnet_id='292f8c1e-...' |
| id                    | f51562ee-da8d-42de-9578-f6f5cb248226             |
| ip_address            | None                                             |
| mac_address           | fa:16:3e:d9:f2:ba                                |
| name                  | port1                                            |
| network_id            | 55dc2f70-0f92-4002-b343-ca34277b0234             |
| option_name           | None                                             |
| option_value          | None                                             |
| port_security_enabled | False                                            |
| project_id            | 4db7c1ed114a4a7fb0f077148155c500                 |
| qos_policy_id         | 5df855e9-a833-49a3-9c82-c0839a5f103f             |
| revision_number       | 6                                                |
| security_group_ids    | 0531cc1a-19d1-4cc7-ada5-49f8b08245be             |
| status                | DOWN                                             |
| subnet_id             | None                                             |
| tags                  | []                                               |
| trunk_details         | None                                             |
| updated_at            | 2017-05-15T08:43:00Z                             |
+-----------------------+--------------------------------------------------+

You can attach networks to a QoS policy. The meaning of this is that any compute port connected to the network will use the network policy by default unless the port has a specific policy attached to it. Internal network owned ports like DHCP and internal router ports are excluded from network policy application.

In order to attach a QoS policy to a network, update an existing network, or initially create the network attached to the policy.

$ openstack network set --qos-policy bw-limiter private

Note

Configuring the proper burst value is very important. If the burst value is set too low, bandwidth usage will be throttled even with a proper bandwidth limit setting. This issue is discussed in various documentation sources, for example in Juniper’s documentation. Burst value for TCP traffic can be set as 80% of desired bandwidth limit value. For example, if the bandwidth limit is set to 1000kbps then enough burst value will be 800kbit. If the configured burst value is too low, achieved bandwidth limit will be lower than expected. If the configured burst value is too high, too few packets could be limited and achieved bandwidth limit would be higher than expected.

The created policy can be associated with an existing floating IP. In order to do this, user extracts the floating IP id to be associated to the already created policy. In the next example, we will assign the bw-limiter policy to the floating IP address 172.16.100.18.

$ openstack floating ip list
+--------------------------------------+---------------------+------------------+------+-----+
| ID                                   | Floating IP Address | Fixed IP Address | Port | ... |
+--------------------------------------+---------------------+------------------+------+-----+
| 1163d127-6df3-44bb-b69c-c0e916303eb3 | 172.16.100.9        | None             | None | ... |
| d0ed7491-3eb7-4c4f-a0f0-df04f10a067c | 172.16.100.18       | None             | None | ... |
| f5a9ed48-2e9f-411c-8787-2b6ecd640090 | 172.16.100.2        | None             | None | ... |
+--------------------------------------+---------------------+------------------+------+-----+
$ openstack floating ip set --qos-policy bw-limiter d0ed7491-3eb7-4c4f-a0f0-df04f10a067c

In order to detach a floating IP from the QoS policy, simply update the floating IP configuration.

$ openstack floating ip set --no-qos-policy d0ed7491-3eb7-4c4f-a0f0-df04f10a067c

Or use the unset action.

$ openstack floating ip unset --qos-policy d0ed7491-3eb7-4c4f-a0f0-df04f10a067c

Floating IPs can be created with a policy attached to them too.

$ openstack floating ip create --qos-policy bw-limiter public
+---------------------+--------------------------------------+
| Field               | Value                                |
+---------------------+--------------------------------------+
| created_at          | 2017-12-06T02:12:09Z                 |
| description         |                                      |
| fixed_ip_address    | None                                 |
| floating_ip_address | 172.16.100.12                        |
| floating_network_id | 4065eb05-cccb-4048-988c-e8c5480a746f |
| id                  | 6a0efeef-462b-4312-b4ad-627cde8a20e6 |
| name                | 172.16.100.12                        |
| port_id             | None                                 |
| project_id          | 916e39e8be52433ba040da3a3a6d0847     |
| qos_policy_id       | 5df855e9-a833-49a3-9c82-c0839a5f103f |
| revision_number     | 1                                    |
| router_id           | None                                 |
| status              | DOWN                                 |
| updated_at          | 2017-12-06T02:12:09Z                 |
+---------------------+--------------------------------------+

The QoS bandwidth limit rules attached to a floating IP will become active when you associate the latter with a port. For example, to associate the previously created floating IP 172.16.100.12 to the instance port with fixed IP 192.168.222.5:

$ openstack port show a7f25e73-4288-4a16-93b9-b71e6fd00862
+-----------------------+--------------------------------------------------+
| Field                 | Value                                            |
+-----------------------+--------------------------------------------------+
| admin_state_up        | UP                                               |
|            ...        |                      ...                         |
| device_id             | 69c03d70-53e8-4030-9c02-675c47f0b06b             |
| device_owner          | compute:nova                                     |
| dns_assignment        | None                                             |
| dns_name              | None                                             |
| extra_dhcp_opts       |                                                  |
| fixed_ips             | ip_address='192.168.222.5', subnet_id='...'      |
| id                    | a7f25e73-4288-4a16-93b9-b71e6fd00862             |
| ip_address            | None                                             |
| mac_address           | fa:16:3e:b5:1a:cc                                |
| name                  |                                                  |
| network_id            | ea602456-3ea8-4989-8981-add6182b4ceb             |
| option_name           | None                                             |
| option_value          | None                                             |
| port_security_enabled | False                                            |
| project_id            | 916e39e8be52433ba040da3a3a6d0847                 |
| qos_policy_id         | None                                             |
| revision_number       | 6                                                |
| security_group_ids    | 77436c73-3a29-42a7-b544-d47f4ea96d54             |
| status                | ACTIVE                                           |
| subnet_id             | None                                             |
| tags                  |                                                  |
| trunk_details         | None                                             |
| updated_at            | 2017-12-05T15:48:54Z                             |
+-----------------------+--------------------------------------------------+
$ openstack floating ip set --port a7f25e73-4288-4a16-93b9-b71e6fd00862 \
    0eeb1f8a-de96-4cd9-a0f6-3f535c409558

Note

For now, the L3 agent floating IP QoS extension only uses bandwidth_limit rules. Other rule types (like DSCP marking) will be silently ignored for floating IPs. A QoS policy that does not contain any bandwidth_limit rules will have no effect when attached to a floating IP.

If floating IP is bound to a port, and both have binding QoS bandwidth rules, the L3 agent floating IP QoS extension ignores the behavior of the port QoS, and installs the rules on the appropriate device in the router namespace.

Each project can have at most one default QoS policy, although it is not mandatory. If a default QoS policy is defined, all new networks created within this project will have this policy assigned, as long as no other QoS policy is explicitly attached during the creation process. If the default QoS policy is unset, no change to existing networks will be made.

In order to set a QoS policy as default, the parameter --default must be used. To unset this QoS policy as default, the parameter --no-default must be used.

$ openstack network qos policy create --default bw-limiter
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| description       |                                      |
| id                | 5df855e9-a833-49a3-9c82-c0839a5f103f |
| is_default        | True                                 |
| name              | bw-limiter                           |
| project_id        | 4db7c1ed114a4a7fb0f077148155c500     |
| rules             | []                                   |
| shared            | False                                |
+-------------------+--------------------------------------+

$ openstack network qos policy set --no-default bw-limiter
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| description       |                                      |
| id                | 5df855e9-a833-49a3-9c82-c0839a5f103f |
| is_default        | False                                |
| name              | bw-limiter                           |
| project_id        | 4db7c1ed114a4a7fb0f077148155c500     |
| rules             | []                                   |
| shared            | False                                |
+-------------------+--------------------------------------+

Administrator enforcement

Administrators are able to enforce policies on project ports or networks. As long as the policy is not shared, the project is not be able to detach any policy attached to a network or port.

If the policy is shared, the project is able to attach or detach such policy from its own ports and networks.

Rule modification

You can modify rules at runtime. Rule modifications will be propagated to any attached port.

$ openstack network qos rule set --max-kbps 2000 --max-burst-kbits 1600 \
    --ingress bw-limiter 92ceb52f-170f-49d0-9528-976e2fee2d6f

$ openstack network qos rule show \
    bw-limiter 92ceb52f-170f-49d0-9528-976e2fee2d6f
+----------------+--------------------------------------+
| Field          | Value                                |
+----------------+--------------------------------------+
| direction      | ingress                              |
| id             | 92ceb52f-170f-49d0-9528-976e2fee2d6f |
| max_burst_kbps | 1600                                 |
| max_kbps       | 2000                                 |
| name           | None                                 |
| project_id     |                                      |
+----------------+--------------------------------------+

Just like with bandwidth limiting, create a policy for DSCP marking rule:

$ openstack network qos policy create dscp-marking
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| description       |                                      |
| id                | d1f90c76-fbe8-4d6f-bb87-a9aea997ed1e |
| is_default        | False                                |
| name              | dscp-marking                         |
| project_id        | 4db7c1ed114a4a7fb0f077148155c500     |
| rules             | []                                   |
| shared            | False                                |
+-------------------+--------------------------------------+

You can create, update, list, delete, and show DSCP markings with the neutron client:

$ openstack network qos rule create --type dscp-marking --dscp-mark 26 \
    dscp-marking
+----------------+--------------------------------------+
| Field          | Value                                |
+----------------+--------------------------------------+
| dscp_mark      | 26                                   |
| id             | 115e4f70-8034-4176-8fe9-2c47f8878a7d |
| name           | None                                 |
| project_id     |                                      |
+----------------+--------------------------------------+
$ openstack network qos rule set --dscp-mark 22 \
    dscp-marking 115e4f70-8034-4176-8fe9-2c47f8878a7d

$ openstack network qos rule list dscp-marking
+--------------------------------------+----------------------------------+
| ID                                   | DSCP Mark                        |
+--------------------------------------+----------------------------------+
| 115e4f70-8034-4176-8fe9-2c47f8878a7d | 22                               |
+--------------------------------------+----------------------------------+

$ openstack network qos rule show \
    dscp-marking 115e4f70-8034-4176-8fe9-2c47f8878a7d
+----------------+--------------------------------------+
| Field          | Value                                |
+----------------+--------------------------------------+
| dscp_mark      | 22                                   |
| id             | 115e4f70-8034-4176-8fe9-2c47f8878a7d |
| name           | None                                 |
| project_id     |                                      |
+----------------+--------------------------------------+

$ openstack network qos rule delete \
    dscp-marking 115e4f70-8034-4176-8fe9-2c47f8878a7d

You can also include minimum bandwidth rules in your policy:

$ openstack network qos policy create bandwidth-control
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| description       |                                      |
| id                | 8491547e-add1-4c6c-a50e-42121237256c |
| is_default        | False                                |
| name              | bandwidth-control                    |
| project_id        | 7cc5a84e415d48e69d2b06aa67b317d8     |
| revision_number   | 1                                    |
| rules             | []                                   |
| shared            | False                                |
+-------------------+--------------------------------------+

$ openstack network qos rule create \
  --type minimum-bandwidth --min-kbps 1000 --egress bandwidth-control
+------------+--------------------------------------+
| Field      | Value                                |
+------------+--------------------------------------+
| direction  | egress                               |
| id         | da858b32-44bc-43c9-b92b-cf6e2fa836ab |
| min_kbps   | 1000                                 |
| name       | None                                 |
| project_id |                                      |
+------------+--------------------------------------+

A policy with a minimum bandwidth ensures best efforts are made to provide no less than the specified bandwidth to each port on which the rule is applied. However, as this feature is not yet integrated with the Compute scheduler, minimum bandwidth cannot be guaranteed.

It is also possible to combine several rules in one policy:

$ openstack network qos rule create --type bandwidth-limit \
    --max-kbps 50000 --max-burst-kbits 50000 bandwidth-control
+----------------+--------------------------------------+
| Field          | Value                                |
+----------------+--------------------------------------+
| id             | 0db48906-a762-4d32-8694-3f65214c34a6 |
| max_burst_kbps | 50000                                |
| max_kbps       | 50000                                |
| name           | None                                 |
| project_id     |                                      |
+----------------+--------------------------------------+

$ openstack network qos policy show bandwidth-control
+-------------------+-------------------------------------------------------------------+
| Field             | Value                                                             |
+-------------------+-------------------------------------------------------------------+
| description       |                                                                   |
| id                | 8491547e-add1-4c6c-a50e-42121237256c                              |
| is_default        | False                                                             |
| name              | bandwidth-control                                                 |
| project_id        | 7cc5a84e415d48e69d2b06aa67b317d8                                  |
| revision_number   | 4                                                                 |
| rules             | [{u'max_kbps': 50000, u'type': u'bandwidth_limit',                |
|                   |   u'id': u'0db48906-a762-4d32-8694-3f65214c34a6',                 |
|                   |   u'max_burst_kbps': 50000,                                       |
|                   |   u'qos_policy_id': u'8491547e-add1-4c6c-a50e-42121237256c'},     |
|                   |  {u'direction':                                                   |
|                   |   u'egress', u'min_kbps': 1000, u'type': u'minimum_bandwidth',    |
|                   |   u'id': u'da858b32-44bc-43c9-b92b-cf6e2fa836ab',                 |
|                   |   u'qos_policy_id': u'8491547e-add1-4c6c-a50e-42121237256c'}]     |
| shared            | False                                                             |
+-------------------+-------------------------------------------------------------------+
Creative Commons Attribution 3.0 License

Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License. See all OpenStack Legal Documents.