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T4977: Add Babel routing protocol
Documentation for https://github.com/vyos/vyos-1x/pull/1800.
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Yuxiang Zhu
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docs/configuration/protocols/babel.rst
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docs/configuration/protocols/babel.rst
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.. _babel:
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####
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Babel
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####
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Babel is a modern routing protocol designed to be robust and efficient
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both in ordinary wired networks and in wireless mesh networks.
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By default, it uses hop-count on wired networks and a variant of ETX
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on wireless links, It can be configured to take radio diversity into account
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and to automatically compute a link's latency and include it in the metric.
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It is defined in :rfc:`8966`.
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Babel a dual stack protocol.
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A single Babel instance is able to perform routing for both IPv4 and IPv6.
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General Configuration
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---------------------
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VyOS does not have a special command to start the Babel process.
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The Babel process starts when the first Babel enabled interface is configured.
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.. cfgcmd:: set protocols babel interface <interface>
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This command specifies a Babel enabled interface by interface name. Both
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the sending and receiving of Babel packets will be enabled on the interface
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specified in this command.
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Optional Configuration
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----------------------
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.. cfgcmd:: set protocols babel parameters diversity
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This command enables routing using radio frequency diversity.
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This is highly recommended in networks with many wireless nodes.
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.. note:: If you enable this, you will probably want to
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set diversity-factor and channel below.
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.. cfgcmd:: set protocols babel parameters diversity-factor <1-256>
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This command sets the multiplicative factor used for diversity routing,
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in units of 1/256; lower values cause diversity to play a more important role
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in route selection.
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The default it 256, which means that diversity plays no role in route
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selection; you will probably want to set that to 128 or less on nodes
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with multiple independent radios.
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.. cfgcmd:: set protocols babel parameters resend-delay <milliseconds>
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This command specifies the time in milliseconds after which an 'important'
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request or update will be resent. The default is 2000 ms.
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.. cfgcmd:: set protocols babel parameters smoothing-half-life <seconds>
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This command specifies the time constant, in seconds, of the smoothing
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algorithm used for implementing hysteresis.
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Larger values reduce route oscillation at the cost of very slightly increasing
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convergence time. The value 0 disables hysteresis, and is suitable for wired
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networks. The default is 4 s.
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Interfaces Configuration
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------------------------
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.. cfgcmd:: set protocols babel interface <interface> type <auto|wired|wireless>
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This command sets the interface type:
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**auto** – automatically determines the interface type.
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**wired** – enables optimisations for wired interfaces.
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**wireless** – disables a number of optimisations that are only correct
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on wired interfaces. Specifying wireless is always correct,
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but may cause slower convergence and extra routing traffic.
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.. cfgcmd:: set protocols babel interface <interface> split-horizon <default|disable|enable>
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This command specifies whether to perform split-horizon on the interface.
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Specifying no babel split-horizon is always correct, while babel split-horizon
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is an optimisation that should only be used on symmetric
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and transitive (wired) networks.
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**default** – enable split-horizon on wired interfaces, and disable
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split-horizon on wireless interfaces.
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**enable** – enable split-horizon on this interfaces.
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**disable** – disable split-horizon on this interfaces.
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.. cfgcmd:: set protocols babel interface <interface> hello-interval <milliseconds>
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This command specifies the time in milliseconds between two scheduled hellos.
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On wired links, Babel notices a link failure within two hello intervals;
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on wireless links, the link quality value is reestimated at every hello
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interval.
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The default is 4000 ms.
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.. cfgcmd:: set protocols babel interface <interface> update-interval <milliseconds>
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This command specifies the time in milliseconds between two scheduled updates.
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Since Babel makes extensive use of triggered updates,
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this can be set to fairly high values on links with little packet loss.
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The default is 20000 ms.
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.. cfgcmd:: set protocols babel interface <interface> rxcost <1-65534>
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This command specifies the base receive cost for this interface.
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For wireless interfaces, it specifies the multiplier used for computing
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the ETX reception cost (default 256);
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for wired interfaces, it specifies the cost that will be advertised to
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neighbours.
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.. cfgcmd:: set protocols babel interface <interface> rtt-decay <1-256>
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This command specifies the decay factor for the exponential moving average
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of RTT samples, in units of 1/256.
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Higher values discard old samples faster. The default is 42.
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.. cfgcmd:: set protocols babel interface <interface> rtt-min <milliseconds>
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This command specifies the minimum RTT, in milliseconds,
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starting from which we increase the cost to a neighbour.
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The additional cost is linear in (rtt - rtt-min). The default is 10 ms.
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.. cfgcmd:: set protocols babel interface <interface> rtt-max <milliseconds>
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This command specifies the maximum RTT, in milliseconds, above which
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we don't increase the cost to a neighbour. The default is 120 ms.
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.. cfgcmd:: set protocols babel interface <interface> max-rtt-penalty <milliseconds>
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This command specifies the maximum cost added to a neighbour because of RTT,
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i.e. when the RTT is higher or equal than rtt-max.
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The default is 150.
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Setting it to 0 effectively disables the use of a RTT-based cost.
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.. cfgcmd:: set protocols babel interface <interface> enable-timestamps
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This command enables sending timestamps with each Hello and IHU message
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in order to compute RTT values.
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It is recommended to enable timestamps on tunnel interfaces.
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.. cfgcmd:: set protocols babel interface <interface> channel <1-254|interfering|noninterfering>
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This command set the channel number that diversity routing uses for this
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interface (see diversity option above).
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**1-254** – interfaces with a channel number interfere with
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interfering interfaces and interfaces with the same channel number.
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**interfering** – interfering interfaces are assumed to interfere with all other channels except
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noninterfering channels.
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**noninterfering** – noninterfering interfaces are assumed to only interfere
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with themselves.
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Redistribution Configuration
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----------------------------
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.. cfgcmd:: set protocols babel redistribute <ipv4|ipv6> <route source>
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This command redistributes routing information from the given route source
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to the Babel process.
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IPv4 route source: bgp, connected, eigrp, isis, kernel, nhrp, ospf, rip, static.
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IPv6 route source: bgp, connected, eigrp, isis, kernel, nhrp, ospfv3, ripng, static.
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.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> access-list <in|out> <number>
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This command can be used to filter the Babel routes using access lists.
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:cfgcmd:`in` and :cfgcmd:`out` this is the direction in which the access
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lists are applied.
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.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> interface <interface> access-list <in|out> <number>
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This command allows you apply access lists to a chosen interface to
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filter the Babel routes.
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.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> prefix-list <in|out> <name>
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This command can be used to filter the Babel routes using prefix lists.
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:cfgcmd:`in` and :cfgcmd:`out` this is the direction in which the prefix
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lists are applied.
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.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> interface <interface> prefix-list <in|out> <name>
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This command allows you apply prefix lists to a chosen interface to
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filter the Babel routes.
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Configuration Example
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---------------------
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Simple Babel configuration using 2 nodes and redistributing connected interfaces.
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**Node 1:**
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.. code-block:: none
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set interfaces loopback lo address 10.1.1.1/32
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set interfaces loopback lo address fd12:3456:dead:beef::1/128
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set protocols babel interface eth0 type wired
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set protocols babel redistribute ipv4 connected
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set protocols babel redistribute ipv6 connected
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**Node 2:**
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.. code-block:: none
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set interfaces loopback lo address 10.2.2.2/32
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set interfaces loopback lo address fd12:3456:beef:dead::2/128
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set protocols babel interface eth0 type wired
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set protocols babel redistribute ipv4 connected
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set protocols babel redistribute ipv6 connected
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@ -7,6 +7,7 @@ Protocols
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:maxdepth: 1
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:includehidden:
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babel
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bfd
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bgp
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failover
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