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doc/install-guide/section_neutron-concepts.xml
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xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0">
<title>Networking concepts</title>
<para>OpenStack Networking (neutron) manages all of the networking facets for
the Virtual Networking Infrastructure (VNI) and the access layer aspects
of the Physical Networking Infrastructure (PNI) in your OpenStack
environment. OpenStack Networking allows tenants to create advanced virtual
network topologies including services such as
<para>OpenStack Networking (neutron) manages all of the networking
facets for the Virtual Networking Infrastructure (VNI) in your
OpenStack environment. OpenStack Networking also manages the access
layer aspects of the Physical Networking Infrastructure (PNI).
Tenants can create advanced virtual network topologies using
OpenStack Networking. These topologies include services such as
<glossterm baseform="firewall">firewalls</glossterm>,
<glossterm baseform="load balancer">load balancers</glossterm>, and
<glossterm baseform="virtual private network (VPN)">
virtual private networks (VPNs)</glossterm>.</para>
<para>Networking provides the following object abstractions: networks,
subnets, and routers. Each has functionality that mimics its
routers, and subnets. Each has a functionality that mimics its
physical counterpart: networks contain subnets, and routers route
traffic between different subnet and networks.</para>
<para>Each router has one gateway that connects to a network, and many
interfaces connected to subnets. Subnets can access machines on
other subnets connected to the same router.</para>
<para>Any given Networking set up has at least one external network.
This network, unlike the other networks, is not merely a virtually
defined network. Instead, it represents the view into a slice of
the external network that is accessible outside the OpenStack
installation. IP addresses on the Networking external network are
accessible by anybody physically on the outside network. Because
this network merely represents a slice of the outside network,
DHCP is disabled on this network.</para>
This external network, unlike the other networks, is not solely a
virtually defined network. It instead provides a view into a slice
of the network accessible outside the OpenStack installation, which
is the outside network. IP addresses on the external network are
accessible by anybody physically on the outside network. DHCP is
disabled on this network.</para>
<para>Machines can access the outside network through the gateway
for the router. For the outside network to access VMs, and for VM's
to access the outside network, routers between the networks are
needed.</para>
<para>In addition to external networks, any Networking set up has one
or more internal networks. These software-defined networks connect
directly to the VMs. Only the VMs on any given internal network,
or those on subnets connected through interfaces to a similar
router, can access VMs connected to that network directly.</para>
<para>For the outside network to access VMs, and vice versa, routers
between the networks are needed. Each router has one gateway that
is connected to a network and many interfaces that are connected
to subnets. Like a physical router, subnets can access machines on
other subnets that are connected to the same router, and machines
can access the outside network through the gateway for the
router.</para>
<para>Additionally, you can allocate IP addresses on external
networks to ports on the internal network. Whenever something is
connected to a subnet, that connection is called a port.You can
associate external network IP addresses with ports to VMs. This
way, entities on the outside network can access VMs.</para>
associate external network IP addresses with ports to VMs.
This way, entities on the outside network can access VMs.</para>
<para>Networking also supports <emphasis role="italic">security
groups</emphasis>. Security groups enable administrators to
define firewall rules in groups. A VM can belong to one or more
security groups, and Networking applies the rules in those security
groups</emphasis>, which enable administrators to define
firewall rules in groups. A VM can belong to one or more
security groups. Networking applies the rules in those security
groups to block or unblock ports, port ranges, or traffic types
for that VM.</para>
<para>Each plug-in that Networking uses has its own concepts. While not
vital to operating Networking, understanding these concepts can help
you set up Networking. All Networking installations use a core plug-in
and a security group plug-in (or just the No-Op security group
plug-in). Additionally, Firewall-as-a-service (FWaaS) and
<simplesect><title>Networking plug-ins</title>
<para>Each plug-in that Networking uses has its own concepts. These
plug-in concepts are not vital to operating Networking.
Understanding these concepts can help you set up the Openstack
Networking service, however. All Networking installations use a core
plug-in and a security group plug-in (or just the No-Op security
group plug-in). Additionally, Firewall-as-a-service (FWaaS) and
Load-balancing-as-a-service (LBaaS) plug-ins are available.</para>
</simplesect>
</section>