Add spec for QoS rule type packet per second
Related-bug: #1912460 Change-Id: Ie9e7054d333dad42a5e874a4fee383361457fde6
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specs/xena/qos_pps_rule.rst
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specs/xena/qos_pps_rule.rst
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..
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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===============================
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QoS Rule Type Packet per Second
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===============================
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RFE: https://bugs.launchpad.net/neutron/+bug/1912460
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Neutron supports bandwidth rate limit for ports and L3 IPs. But packet
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rate limit (packet per second) is not available, although it is a common
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measurement.
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So, this spec describes adding a new QoS rule type packet per second (pps).
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Problem Description
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===================
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Packet per second is a very general network performance metric.
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Like bandwidth, it is usually used to evaluate the packet forwarding
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performance of a device.
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For cloud providers, to limit the packet per second (pps)
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of VM NIC is popular and sometimes essential. Transit large set of
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packets for VM in physical compute hosts will consume the
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CPU and physical NIC I/O performance. For small packets, even if the
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bandwidth is low, the pps can still be higher. Without the limitation,
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it can be an attack point inside the cloud while some VMs are becoming
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hacked.
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For L2 drivers like ovs and ovn, it may get extremly high usage of
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CPU when user send small packet (typically 64B small) from
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the VM to the others, even if the device has lower QoS bandwidth limitation.
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Then your host services and other users' VMs will be under a higher
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failure point.
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For network quality assurance, the resource consumption of the system
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is determined according to the user's VM specifications. With the pps
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limitation, the VM will not consume more CPU with smaller bandwidth.
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Proposed Change
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===============
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Adding new API extension to QoS service plugin to allow CURD actions for
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packet rate limit (packet per second) rule.
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.. note:: We will not elaborate the real limitation in L2/L3 backend,
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this spec only shows how we add a new QoS rule type.
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Server side changes
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-------------------
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A new API extension of Neutron will be added with new resource
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``PacketRateLimitRule``:
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::
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qos_apidef.SUB_RESOURCE_ATTRIBUTE_MAP = {
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'packet_rate_limit_rules': {
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'parent': qos_apidef._PARENT,
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'parameters': {
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qos_apidef._QOS_RULE_COMMON_FIELDS,
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'max_kpps': {
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'allow_post': True, 'allow_put': True,
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'convert_to': converters.convert_to_int,
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'is_visible': True,
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'is_filter': True,
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'is_sort_key': True,
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'validate': {
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'type:range': [0, db_const.DB_INTEGER_MAX_VALUE]}
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},
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'max_burst_kpps': {
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'allow_post': True, 'allow_put': True,
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'is_visible': True, 'default': 0,
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'is_filter': True,
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'is_sort_key': True,
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'convert_to': converters.convert_to_int,
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'validate': {
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'type:range': [0, db_const.DB_INTEGER_MAX_VALUE]}
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},
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'direction': {
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'allow_post': True,
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'allow_put': True,
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'is_visible': True,
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'is_filter': True,
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'is_sort_key': True,
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'default': constants.EGRESS_DIRECTION,
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'validate': {
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'type:values': constants.VALID_DIRECTIONS}
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}
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}
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}
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}
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.. note:: The unit for the rate and burst is kilo (1000) packets per second,
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so the value range will be 1 kpps to 2147 gpps.
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Potential agent side enhancements
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---------------------------------
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Each of the following will be an independent and huge proposal, we will
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not describe the detail here.
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* apply pps rule to L3 IPs in agent side by iptables rule [1]_.
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* apply pps rule to VM port by ovs meter [2]_ [3]_ [4]_.
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* apply pps rule to router ports (gateway port, router interface) by iptables rule.
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* apply pps rule to L3 IPs and ports to OVN related devices by ovs meter.
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User use cases
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--------------
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After the L2/L3 backends have the real abilities to limit the pps,
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users can use the pps rule in the following scenarios:
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* "pps" rule for floating IP, using the L3 agent
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* "pps" rule for floating IP, using OVN L3 agent
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* "pps" rule for gateway IP, using the L3 agent
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* "pps" rule for gateway IP, using OVN L3 agent
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* "pps" rule for ML2 OVS VM ports
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* "pps" rule for ML2 OVN VM ports
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* "pps" rule for router gateway or interface ports
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Data Model Impact
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-----------------
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Add table ``qos_packet_rate_limit_rules``:
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::
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op.create_table(
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'qos_packet_rate_limit_rules',
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sa.Column('id', sa.String(36), nullable=False,
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index=True),
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sa.Column('qos_policy_id', sa.String(36),
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nullable=False, index=True),
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sa.Column('max_kpps', sa.Integer()),
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sa.Column('max_burst_kpps', sa.Integer()),
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sa.Column('direction', sa.Enum(constants.EGRESS_DIRECTION,
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constants.INGRESS_DIRECTION,
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name="directions"),
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nullable=False,
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server_default=constants.EGRESS_DIRECTION),
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sa.PrimaryKeyConstraint('id'),
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sa.ForeignKeyConstraint(['qos_policy_id'], ['qos_policies.id'],
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ondelete='CASCADE')
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)
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Add DB model ``QosPacketRateLimitRule``:
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::
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class QosPacketRateLimitRule(model_base.HasId, model_base.BASEV2):
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__tablename__ = 'qos_packet_rate_limit_rules'
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qos_policy_id = sa.Column(sa.String(36),
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sa.ForeignKey('qos_policies.id',
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ondelete='CASCADE'),
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nullable=False)
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max_kpps = sa.Column(sa.Integer)
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max_burst_kpps = sa.Column(sa.Integer)
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revises_on_change = ('qos_policy',)
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qos_policy = sa.orm.relationship(QosPolicy, load_on_pending=True)
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direction = sa.Column(sa.Enum(constants.EGRESS_DIRECTION,
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constants.INGRESS_DIRECTION,
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name="directions"),
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default=constants.EGRESS_DIRECTION,
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server_default=constants.EGRESS_DIRECTION,
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nullable=False)
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__table_args__ = (
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sa.UniqueConstraint(
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qos_policy_id, direction,
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name="qos_packet_rate_limit_rules0qos_policy_id0direction"),
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model_base.BASEV2.__table_args__
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)
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With OVO object:
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::
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@base.NeutronObjectRegistry.register
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class QosPacketRateLimitRule(QosRule):
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db_model = qos_db_model.QosPacketRateLimitRule
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fields = {
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'max_kpps': obj_fields.IntegerField(nullable=True),
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'max_burst_kpps': obj_fields.IntegerField(nullable=True),
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'direction': common_types.FlowDirectionEnumField(
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default=constants.EGRESS_DIRECTION)
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}
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duplicates_compare_fields = ['direction']
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rule_type = constants.RULE_TYPE_PACKET_RATE_LIMIT
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REST API Impact
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---------------
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GET: List packet rate limit rules for QoS policy
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* /v2.0/qos/policies/{policy_id}/packet_rate_limit_rules
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Response:
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::
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{
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"packet_rate_limit_rules": [
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{
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"id": "5f126d84-551a-4dcf-bb01-0e9c0df0c793",
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"max_kpps": 10000,
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"max_burst_kpps": 0,
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"direction": "egress"
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}
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]
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}
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POST: Create packet rate limit rule
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* /v2.0/qos/policies/{policy_id}/packet_rate_limit_rules
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Request:
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::
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{
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"packet_rate_limit_rule": {
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"max_kpps": "10000"
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}
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}
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Response:
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::
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{
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"packet_rate_limit_rule": {
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"id": "5f126d84-551a-4dcf-bb01-0e9c0df0c793",
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"max_kpps": 10000,
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"max_burst_kpps": 0,
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"direction": "egress"
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}
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}
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GET: Show packet rate limit rule details
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* /v2.0/qos/policies/{policy_id}/packet_rate_limit_rules/{rule_id}
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Response:
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::
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{
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"packet_rate_limit_rule": {
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"id": "5f126d84-551a-4dcf-bb01-0e9c0df0c793",
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"max_kpps": 10000,
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"max_burst_kpps": 0,
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"direction": "egress"
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}
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}
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PUT: Update packet rate limit rule
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* /v2.0/qos/policies/{policy_id}/packet_rate_limit_rules/{rule_id}
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Request:
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::
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{
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"packet_rate_limit_rule": {
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"max_kpps": 10000
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}
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}
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Response:
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::
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{
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"packet_rate_limit_rule": {
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"id": "5f126d84-551a-4dcf-bb01-0e9c0df0c794",
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"max_kpps": "10000"
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}
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}
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DELETE: Delete packet rate limit rule
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* /v2.0/qos/policies/{policy_id}/packet_rate_limit_rules/{rule_id}
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And, neutron will allow attaching new ``PacketRateLimitRule`` to QoS policy.
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The Neutron basic workflow
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--------------------------
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1. User creates QoS policy
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2. Creates packet rate limit rules with multiple directions to this QoS policy
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3. Attaching this QoS policy to a port
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4. (No available) related L2 driver apply PPS limitation driver rule to the port
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5. Attaching this QoS policy to a L3 IP (floating IP or gateway IP).
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6. (No available) related L3 driver apply PPS limitation driver rule to the IP
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Implementation
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==============
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Assignee(s)
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-----------
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* LIU Yulong <i@liuyulong.me>
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Work Items
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----------
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* Adding API extension and DB models for neutron server.
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* Testing.
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* Documentation.
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Dependencies
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============
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None
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Testing
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=======
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Unit test cases to verify the DB rules are created/updated/deleted.
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References
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==========
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.. [1] https://linux.die.net/man/8/iptables
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.. [2] http://workshop.netfilter.org/2017/wiki/images/d/db/Nfws-ovs-metering.pdf
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.. [3] http://www.openvswitch.org//support/dist-docs/ovs-ofctl.8.txt
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.. [4] https://github.com/openvswitch/ovs/blob/master/NEWS#L312
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