375 lines
15 KiB
ReStructuredText
375 lines
15 KiB
ReStructuredText
.. _intro-os-networking:
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====================
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OpenStack Networking
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====================
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OpenStack Networking allows you to create and manage network objects,
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such as networks, subnets, and ports, which other OpenStack services
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can use. Plug-ins can be implemented to accommodate different
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networking equipment and software, providing flexibility to OpenStack
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architecture and deployment.
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The Networking service, code-named neutron, provides an API that lets you
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define network connectivity and addressing in the cloud. The Networking
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service enables operators to leverage different networking technologies
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to power their cloud networking. The Networking service also provides an
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API to configure and manage a variety of network services ranging from L3
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forwarding and Network Address Translation (NAT) to perimeter firewalls, and
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virtual private networks.
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It includes the following components:
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API server
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The OpenStack Networking API includes support for Layer 2 networking
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and IP Address Management (IPAM), as well as an extension for a Layer 3
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router construct that enables routing between Layer 2 networks and gateways
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to external networks. OpenStack Networking includes a growing list of
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plug-ins that enable interoperability with various commercial and open
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source network technologies, including routers, switches, virtual
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switches and software-defined networking (SDN) controllers.
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OpenStack Networking plug-in and agents
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Plugs and unplugs ports, creates networks or subnets, and provides
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IP addressing. The chosen plug-in and agents differ depending on the
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vendor and technologies used in the particular cloud. It is
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important to mention that only one plug-in can be used at a time.
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Messaging queue
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Accepts and routes RPC requests between agents to complete API operations.
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Message queue is used in the ML2 plug-in for RPC between the neutron
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server and neutron agents that run on each hypervisor, in the ML2
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mechanism drivers for Open vSwitch and Linux bridge.
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Concepts
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~~~~~~~~
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To configure rich network topologies, you can create and configure networks
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and subnets and instruct other OpenStack services like Compute to attach
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virtual devices to ports on these networks.
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OpenStack Compute is a prominent consumer of OpenStack Networking to provide
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connectivity for its instances.
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In particular, OpenStack Networking supports each project having multiple
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private networks and enables projects to choose their own IP addressing scheme,
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even if those IP addresses overlap with those that other projects use. There
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are two types of network, project and provider networks. It is possible to
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share any of these types of networks among projects as part of the network
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creation process.
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.. _intro-os-networking-provider:
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Provider networks
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-----------------
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Provider networks offer layer-2 connectivity to instances with optional
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support for DHCP and metadata services. These networks connect, or map, to
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existing layer-2 networks in the data center, typically using VLAN (802.1q)
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tagging to identify and separate them.
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Provider networks generally offer simplicity, performance, and reliability
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at the cost of flexibility. By default only administrators can create or
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update provider networks because they require configuration of physical
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network infrastructure. It is possible to change the user who is allowed to
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create or update provider networks with the following parameters of
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``policy.yaml``:
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* ``create_network:provider:physical_network``
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* ``update_network:provider:physical_network``
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.. warning::
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The creation and modification of provider networks enables use of
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physical network resources, such as VLAN-s. Enable these changes
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only for trusted projects.
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Also, provider networks only handle layer-2 connectivity for instances, thus
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lacking support for features such as routers and floating IP addresses.
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In many cases, operators who are already familiar with virtual networking
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architectures that rely on physical network infrastructure for layer-2,
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layer-3, or other services can seamlessly deploy the OpenStack Networking
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service. In particular, provider networks appeal to operators looking to
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migrate from the Compute networking service (nova-network) to the OpenStack
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Networking service. Over time, operators can build on this minimal
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architecture to enable more cloud networking features.
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In general, the OpenStack Networking software components that handle layer-3
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operations impact performance and reliability the most. To improve performance
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and reliability, provider networks move layer-3 operations to the physical
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network infrastructure.
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In one particular use case, the OpenStack deployment resides in a mixed
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environment with conventional virtualization and bare-metal hosts that use a
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sizable physical network infrastructure. Applications that run inside the
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OpenStack deployment might require direct layer-2 access, typically using
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VLANs, to applications outside of the deployment.
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Routed provider networks
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------------------------
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Routed provider networks offer layer-3 connectivity to instances. These
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networks map to existing layer-3 networks in the data center. More
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specifically, the network maps to multiple layer-2 segments, each of which is
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essentially a provider network. Each has a router gateway attached to it which
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routes traffic between them and externally. The Networking service does not
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provide the routing.
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Routed provider networks offer performance at scale that is difficult to
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achieve with a plain provider network at the expense of guaranteed layer-2
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connectivity.
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Neutron port could be associated with only one network segment,
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but there is an exception for OVN distributed services like OVN Metadata.
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See :ref:`config-routed-provider-networks` for more information.
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.. _intro-os-networking-selfservice:
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Self-service networks
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---------------------
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Self-service networks primarily enable general (non-privileged) projects
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to manage networks without involving administrators. These networks are
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entirely virtual and require virtual routers to interact with provider
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and external networks such as the Internet. Self-service networks also
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usually provide DHCP and metadata services to instances.
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In most cases, self-service networks use overlay protocols such as VXLAN
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or GRE because they can support many more networks than layer-2 segmentation
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using VLAN tagging (802.1q). Furthermore, VLANs typically require additional
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configuration of physical network infrastructure.
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IPv4 self-service networks typically use private IP address ranges (RFC1918)
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and interact with provider networks via source NAT on virtual routers.
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Floating IP addresses enable access to instances from provider networks
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via destination NAT on virtual routers. IPv6 self-service networks always
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use public IP address ranges and interact with provider networks via
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virtual routers with static routes.
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The Networking service implements routers using a layer-3 agent that typically
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resides at least one network node. Contrary to provider networks that connect
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instances to the physical network infrastructure at layer-2, self-service
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networks must traverse a layer-3 agent. Thus, oversubscription or failure
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of a layer-3 agent or network node can impact a significant quantity of
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self-service networks and instances using them. Consider implementing one or
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more high-availability features to increase redundancy and performance
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of self-service networks.
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Users create project networks for connectivity within projects. By default,
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they are fully isolated and are not shared with other projects. OpenStack
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Networking supports the following types of network isolation and overlay
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technologies.
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Flat
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All instances reside on the same network, which can also be shared
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with the hosts. No VLAN tagging or other network segregation takes place.
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VLAN
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Networking allows users to create multiple provider or project networks
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using VLAN IDs (802.1Q tagged) that correspond to VLANs present in the
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physical network. This allows instances to communicate with each other
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across the environment. They can also communicate with dedicated servers,
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firewalls, and other networking infrastructure on the same layer 2 VLAN.
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GRE and VXLAN
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VXLAN and GRE are encapsulation protocols that create overlay networks
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to activate and control communication between compute instances. A
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Networking router is required to allow traffic to flow outside of the
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GRE or VXLAN project network. A router is also required to connect
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directly-connected project networks with external networks, including the
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Internet. The router provides the ability to connect to instances directly
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from an external network using floating IP addresses.
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.. image:: figures/NetworkTypes.png
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:width: 100%
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:alt: Project and provider networks
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Subnets
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-------
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A block of IP addresses and associated configuration state. This
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is also known as the native IPAM (IP Address Management) provided by the
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networking service for both project and provider networks.
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Subnets are used to allocate IP addresses when new ports are created on a
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network.
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Subnet pools
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------------
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End users normally can create subnets with any valid IP addresses without other
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restrictions. However, in some cases, it is nice for the admin or the project
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to pre-define a pool of addresses from which to create subnets with automatic
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allocation.
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Using subnet pools constrains what addresses can be used by requiring that
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every subnet be within the defined pool. It also prevents address reuse or
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overlap by two subnets from the same pool.
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See :ref:`config-subnet-pools` for more information.
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Ports
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-----
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A port is a connection point for attaching a single device, such as the NIC
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of a virtual server, to a virtual network. The port also describes the
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associated network configuration, such as the MAC and IP addresses to be
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used on that port.
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Routers
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-------
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Routers provide virtual layer-3 services such as routing and NAT
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between self-service and provider networks or among self-service
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networks belonging to a project. The Networking service uses a
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layer-3 agent to manage routers via namespaces.
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Security groups
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---------------
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Security groups provide a container for virtual firewall rules that control
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ingress (inbound to instances) and egress (outbound from instances) network
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traffic at the port level. Security groups use a default deny policy and
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only contain rules that allow specific traffic. Each port can reference one
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or more security groups in an additive fashion. The firewall driver
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translates security group rules to a configuration for the underlying packet
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filtering technology such as ``iptables``.
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Each project contains a ``default`` security group that allows all egress
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traffic and denies all ingress traffic. You can change the rules in the
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``default`` security group. If you launch an instance without specifying a
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security group, the ``default`` security group automatically applies to it.
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Similarly, if you create a port without specifying a security group, the
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``default`` security group automatically applies to it.
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.. note::
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If you use the metadata service, removing the default egress rules denies
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access to TCP port 80 on 169.254.169.254, thus preventing instances from
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retrieving metadata.
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Security group rules are stateful. Thus, allowing ingress TCP port 22 for
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secure shell automatically creates rules that allow return egress traffic
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and ICMP error messages involving those TCP connections.
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By default, all security groups contain a series of basic (sanity) and
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anti-spoofing rules that perform the following actions:
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* Allow egress traffic only if it uses the source MAC and IP addresses
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of the port for the instance, source MAC and IP combination in
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``allowed-address-pairs``, or valid MAC address (port or
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``allowed-address-pairs``) and associated EUI64 link-local IPv6 address.
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* Allow egress DHCP discovery and request messages that use the source MAC
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address of the port for the instance and the unspecified IPv4 address
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(0.0.0.0).
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* Allow ingress DHCP and DHCPv6 responses from the DHCP server on the
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subnet so instances can acquire IP addresses.
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* Deny egress DHCP and DHCPv6 responses to prevent instances from
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acting as DHCP(v6) servers.
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* Allow ingress/egress ICMPv6 MLD, neighbor solicitation, and neighbor
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discovery messages so instances can discover neighbors and join
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multicast groups.
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* Deny egress ICMPv6 router advertisements to prevent instances from acting
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as IPv6 routers and forwarding IPv6 traffic for other instances.
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* Allow egress ICMPv6 MLD reports (v1 and v2) and neighbor solicitation
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messages that use the source MAC address of a particular instance and
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the unspecified IPv6 address (::). Duplicate address detection (DAD) relies
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on these messages.
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* Allow egress non-IP traffic from the MAC address of the port for the
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instance and any additional MAC addresses in ``allowed-address-pairs`` on
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the port for the instance.
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Although non-IP traffic, security groups do not implicitly allow all ARP
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traffic. Separate ARP filtering rules prevent instances from using ARP
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to intercept traffic for another instance. You cannot disable or remove
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these rules.
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You can disable security groups including basic and anti-spoofing rules
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by setting the port attribute ``port_security_enabled`` to ``False``.
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Extensions
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----------
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The OpenStack Networking service is extensible. Extensions serve two
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purposes: they allow the introduction of new features in the API
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without requiring a version change and they allow the introduction of
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vendor specific niche functionality. Applications can programmatically
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list available extensions by performing a GET on the
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:code:`/extensions` URI. Note that this is a versioned request; that
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is, an extension available in one API version might not be available
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in another.
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DHCP
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----
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The optional DHCP service manages IP addresses for instances on provider
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and self-service networks. The Networking service implements the DHCP
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service using an agent that manages ``qdhcp`` namespaces and the
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``dnsmasq`` service.
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Metadata
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--------
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The optional metadata service provides an API for instances to obtain
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metadata such as SSH keys.
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Service and component hierarchy
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Server
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------
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* Provides API, manages database, etc.
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Plug-ins
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--------
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* Manages agents
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Agents
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------
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* Provides layer 2/3 connectivity to instances
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* Handles physical-virtual network transition
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* Handles metadata, etc.
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Layer 2 (Ethernet and Switching)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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* Linux Bridge
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* OVS
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Layer 3 (IP and Routing)
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^^^^^^^^^^^^^^^^^^^^^^^^
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* L3
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* DHCP
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Miscellaneous
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^^^^^^^^^^^^^
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* Metadata
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Services
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--------
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Routing services
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^^^^^^^^^^^^^^^^
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VPNaaS
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^^^^^^
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The Virtual Private Network-as-a-Service (VPNaaS) is a neutron
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extension that introduces the VPN feature set.
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LBaaS
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^^^^^
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The Load-Balancer-as-a-Service (LBaaS) API provisions and configures
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load balancers. The reference implementation is based on the HAProxy
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software load balancer. See the `Octavia project
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<https://docs.openstack.org/octavia/latest/>`_ for more information.
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