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doc: update overview.rst for the new millennium
Provide a more succinct summary of what FRR is, what it does, where it sits in the network stack. Also remove some outdated comments about features. Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>
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Overview
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********
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`FRR`_ is a routing software package that provides TCP/IP based routing
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services with routing protocols support such as BGP, RIP, OSPF, IS-IS and more
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(see :ref:`supported-protocols`). FRR also supports
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special BGP Route Reflector and Route Server behavior. In addition to
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traditional IPv4 routing protocols, FRR also supports IPv6 routing protocols.
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With an SNMP daemon that supports the AgentX protocol, FRR provides routing
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protocol MIB read-only access (:ref:`snmp-support`).
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`FRR`_ is a fully featured, high performance, free software IP routing suite.
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FRR uses an advanced software architecture to provide you with a high quality,
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multi server routing engine. FRR has an interactive user interface for each
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routing protocol and supports common client commands. Due to this design, you
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can add new protocol daemons to FRR easily. You can use FRR library as your
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program's client user interface.
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FRR implements all standard routing protocols such as BGP, RIP, OSPF, IS-IS and
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more (see :ref:`feature-matrix`), as well as many of their extensions.
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FRR is distributed under the GNU General Public License.
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FRR is a high performance suite written primarily in C. It can easily handle
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full Internet routing tables and is suitable for use on hardware ranging from
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cheap SBCs to commercial grade routers. It is actively used in production by
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hundreds of companies, universities, research labs and governments.
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FRR is distributed under GPLv2, with development modeled after the Linux
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kernel. Anyone may contribute features, bug fixes, tools, documentation
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updates, or anything else.
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FRR is a fork of `Quagga <http://www.quagga.net/>`_.
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.. _about-frr:
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About FRR
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=========
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Today, TCP/IP networks are covering all of the world. The Internet has been
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deployed in many countries, companies, and to the home. When you connect to
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the Internet your packet will pass many routers which have TCP/IP routing
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functionality.
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A system with FRR installed acts as a dedicated router. With FRR, your machine
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exchanges routing information with other routers using routing protocols. FRR
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uses this information to update the kernel routing table so that the right data
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goes to the right place. You can dynamically change the configuration and you
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may view routing table information from the FRR terminal interface.
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Adding to routing protocol support, FRR can setup interface's flags,
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interface's address, static routes and so on. If you have a small network, or
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a stub network, or xDSL connection, configuring the FRR routing software is
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very easy. The only thing you have to do is to set up the interfaces and put a
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few commands about static routes and/or default routes. If the network is
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rather large, or if the network structure changes frequently, you will want to
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take advantage of FRR's dynamic routing protocol support for protocols such as
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RIP, OSPF, IS-IS or BGP.
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Traditionally, UNIX based router configuration is done by *ifconfig* and
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*route* commands. Status of routing table is displayed by *netstat* utility.
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Almost of these commands work only if the user has root privileges. FRR has a
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different system administration method. There are two user modes in FRR. One
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is normal mode, the other is enable mode. Normal mode user can only view
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system status, enable mode user can change system configuration. This UNIX
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account independent feature will be great help to the router administrator.
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Currently, FRR supports common unicast routing protocols, that is BGP, OSPF,
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RIP and IS-IS. Upcoming for MPLS support, an implementation of LDP is
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currently being prepared for merging. Implementations of BFD and PIM-SSM
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(IPv4) also exist, but are not actively being worked on.
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The ultimate goal of the FRR project is making a production-grade, high
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quality, featureful and free IP routing software suite.
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.. _how-to-get-frr:
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How to get FRR
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==============
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@ -79,25 +37,46 @@ For instructions on installing from source, refer to the
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`developer documentation <http://docs.frrouting.org/projects/dev-guide/en/latest/>`_.
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.. _about-frr:
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About FRR
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=========
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FRR provides IP routing services. Its role in a networking stack is to exchange
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routing information with other routers, make routing and policy decisions, and
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inform other layers of these decisions. In the most common scenario, FRR
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installs routing decisions into the OS kernel, allowing the kernel networking
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stack to make the corresponding forwarding decisions.
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In addition to dynamic routing FRR supports the full range of L3 configuration,
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including static routes, addresses, router advertisements etc. It has some
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light L2 functionality as well, but this is mostly left to the platform. This
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makes it suitable for deployments ranging from small home networks with static
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routes to Internet exchanges running full Internet tables.
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FRR runs on all modern \*NIX operating systems, including Linux and the BSDs.
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Feature support varies by platform; see the :ref:`feature-matrix`.
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System Architecture
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===================
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-------------------
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.. index:: System architecture
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.. index:: Software architecture
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.. index:: Software internals
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Traditional routing software is made as a one process program which provides
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all of the routing protocol functionalities. FRR takes a different approach.
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FRR is a suite of daemons that work together to build the routing table. There
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is a daemon for each major supported protocol as well as a middleman daemon
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(*Zebra*) which serves as the broker between these daemons and the kernel.
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FRR is a suite of daemons that work together to build the routing table. Each
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major protocol is implemented in its own daemon, and these daemons talk to a
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middleman daemon (*zebra*), which is responsible for coordinating routing
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decisions and talking to the dataplane.
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This architecture allows for high resiliency, since an error, crash or exploit
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in one protocol daemon will generally not affect the others. It is also
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in one protocol daemon will generally not affect the others. It is also
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flexible and extensible since the modularity makes it easy to implement new
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protocols and tie them into the suite.
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protocols and tie them into the suite. Additionally, each daemon implements a
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plugin system allowing new functionality to be loaded at runtime.
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An illustration of the large scale architecture is given below.
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@ -121,17 +100,23 @@ An illustration of the large scale architecture is given below.
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+-------------+ +------------------+ +-------------+
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The multi-process architecture brings extensibility, modularity and
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maintainability. All of the FRR daemons can be managed through a single
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integrated user interface shell called *vtysh*. *vtysh* connects to each
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daemon through a UNIX domain socket and then works as a proxy for user input.
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In addition to a unified frontend, *vtysh* also provides the ability to
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configure all the daemons using a single configuration file through the
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integrated configuration mode avoiding the problem of having to maintain a
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separate configuration file for each daemon.
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All of the FRR daemons can be managed through a single integrated user
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interface shell called *vtysh*. *vtysh* connects to each daemon through a UNIX
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domain socket and then works as a proxy for user input. In addition to a
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unified frontend, *vtysh* also provides the ability to configure all the
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daemons using a single configuration file through the integrated configuration
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mode. This avoids the overhead of maintaining a separate configuration file for
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each daemon.
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FRR is currently currently implementing a new internal configuration system
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based on YANG data models. When this work is completed, FRR will be a fully
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programmable routing stack.
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.. _supported-platforms:
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Supported Platforms
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===================
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-------------------
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.. index:: Supported platforms
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.. index:: FRR on other systems
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@ -150,7 +135,7 @@ us know if you can get FRR to run on a platform which is not listed below:
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Versions of these platforms that are older than around 2 years from the point
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of their original release (in case of GNU/Linux, this is since the kernel's
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release on https://kernel.org/) may need some work. Similarly, the following
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release on https://kernel.org/) may need some work. Similarly, the following
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platforms may work with some effort:
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- Solaris
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@ -162,14 +147,15 @@ Recent versions of the following compilers are well tested:
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- LLVM's Clang
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- Intel's ICC
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.. _supported-protocols:
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.. _feature-matrix:
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Supported Protocols vs. Platform
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================================
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Feature Matrix
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^^^^^^^^^^^^^^
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The following table lists all protocols cross-refrenced to all operating
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systems that have at least CI build tests. Note that for features, only
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features with system dependencies are included here.
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The following table lists all protocols cross-referenced to all operating
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systems that have at least CI build tests. Note that for features, only
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features with system dependencies are included here; if you don't see the
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feature you're interested in, it should be supported on your platform.
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.. role:: mark
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