fac23cb047
Since we have now a niceness gate, let's remove the known failures. Change-Id: I01684aee61e18e76f6523a466e28b8252e577f6f
131 lines
6.6 KiB
XML
131 lines
6.6 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="module002-ch003-neutron-use-cases">
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<title>Neutron Use Cases</title>
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<para>As of now you must be wondering, how to use these awesome
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features that OpenStack Networking has given to us.</para>
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<para><guilabel><anchor xml:id="h.lrsgdytf1mh5"/>Use Case: Single Flat
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Network</guilabel></para>
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<para>In the simplest use case, a single OpenStack Networking
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network exists. This is a "shared" network, meaning it is
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visible to all tenants via the OpenStack Networking API.
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Tenant VMs have a single NIC, and receive a fixed IP
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address from the subnet(s) associated with that network.
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This essentially maps to the FlatManager and
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FlatDHCPManager models provided by OpenStack Compute.
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Floating IPs are not supported.</para>
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<para>It is common that such an OpenStack Networking network
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is a "provider network", meaning it was created by the
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OpenStack administrator to map directly to an existing
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physical network in the data center. This allows the
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provider to use a physical router on that data center
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network as the gateway for VMs to reach the outside world.
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For each subnet on an external network, the gateway
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configuration on the physical router must be manually
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configured outside of OpenStack.</para>
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<figure>
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<title>Single Flat Network</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="figures/image34.png"/>
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</imageobject>
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</mediaobject>
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</figure>
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<para><guilabel>Use Case: Multiple Flat
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Network</guilabel></para>
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<para>This use case is very similar to the above Single Flat
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Network use case, except that tenants see multiple shared
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networks via the OpenStack Networking API and can choose
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which network (or networks) to plug into.</para>
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<figure>
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<title>Multiple Flat Network</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="figures/image35.png"/>
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</imageobject>
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</mediaobject>
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</figure>
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<para><guilabel>Use Case: Mixed Flat and Private
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Network</guilabel></para>
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<para>This use case is an extension of the above flat network
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use cases, in which tenants also optionally have access to
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private per-tenant networks. In addition to seeing one or
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more shared networks via the OpenStack Networking API,
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tenants can create additional networks that are only
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visible to users of that tenant. When creating VMs, those
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VMs can have NICs on any of the shared networks and/or any
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of the private networks belonging to the tenant. This
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enables the creation of "multi-tier" topologies using VMs
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with multiple NICs. It also supports a model where a VM
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acting as a gateway can provide services such as routing,
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NAT, or load balancing.</para>
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<figure>
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<title>Mixed Flat and Private Network</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="figures/image36.png"/>
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</imageobject>
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</mediaobject>
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</figure>
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<para><guilabel>Use Case: Provider Router with Private
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Networks</guilabel></para>
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<para>This use provides each tenant with one or more private
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networks, which connect to the outside world via an
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OpenStack Networking router. The case where each tenant
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gets exactly one network in this form maps to the same
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logical topology as the VlanManager in OpenStack Compute
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(of course, OpenStack Networking doesn't require VLANs).
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Using the OpenStack Networking API, the tenant would only
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see a network for each private network assigned to that
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tenant. The router object in the API is created and owned
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by the cloud admin.</para>
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<para>This model supports giving VMs public addresses using
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"floating IPs", in which the router maps public addresses
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from the external network to fixed IPs on private
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networks. Hosts without floating IPs can still create
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outbound connections to the external network, as the
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provider router performs SNAT to the router's external IP.
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The IP address of the physical router is used as the
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gateway_ip of the external network subnet, so the provider
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has a default router for Internet traffic.</para>
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<para>The router provides L3 connectivity between private
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networks, meaning that different tenants can reach each
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others instances unless additional filtering (e.g.,
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security groups) is used. Because there is only a single
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router, tenant networks cannot use overlapping IPs. Thus,
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it is likely that the admin would create the private
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networks on behalf of tenants.</para>
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<figure>
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<title>Provider Router with Private Networks</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="figures/image37.png"/>
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</imageobject>
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</mediaobject>
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</figure>
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<para><guilabel>Use Case: Per-tenant Routers with Private
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Networks</guilabel></para>
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<para>A more advanced router scenario in which each tenant
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gets at least one router, and potentially has access to
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the OpenStack Networking API to create additional routers.
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The tenant can create their own networks, potentially
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uplinking those networks to a router. This model enables
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tenant-defined multi-tier applications, with each tier
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being a separate network behind the router. Since there
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are multiple routers, tenant subnets can be overlapping
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without conflicting, since access to external networks all
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happens via SNAT or Floating IPs. Each router uplink and
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floating IP is allocated from the external network
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subnet.</para>
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<figure>
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<title>Per-tenant Routers with Private Networks</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="figures/image38.png"/>
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</imageobject>
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</mediaobject>
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</figure>
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</chapter> |