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authorYuxiang Zhu <vfreex@gmail.com>2023-02-06 19:00:44 +0800
committerYuxiang Zhu <vfreex@gmail.com>2023-02-06 19:00:44 +0800
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T4977: Add Babel routing protocol
Documentation for https://github.com/vyos/vyos-1x/pull/1800.
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+.. _babel:
+
+####
+Babel
+####
+
+Babel is a modern routing protocol designed to be robust and efficient
+both in ordinary wired networks and in wireless mesh networks.
+By default, it uses hop-count on wired networks and a variant of ETX
+on wireless links, It can be configured to take radio diversity into account
+and to automatically compute a link's latency and include it in the metric.
+It is defined in :rfc:`8966`.
+
+Babel a dual stack protocol.
+A single Babel instance is able to perform routing for both IPv4 and IPv6.
+
+General Configuration
+---------------------
+
+VyOS does not have a special command to start the Babel process.
+The Babel process starts when the first Babel enabled interface is configured.
+
+.. cfgcmd:: set protocols babel interface <interface>
+
+ This command specifies a Babel enabled interface by interface name. Both
+ the sending and receiving of Babel packets will be enabled on the interface
+ specified in this command.
+
+Optional Configuration
+----------------------
+
+.. cfgcmd:: set protocols babel parameters diversity
+
+ This command enables routing using radio frequency diversity.
+ This is highly recommended in networks with many wireless nodes.
+
+ .. note:: If you enable this, you will probably want to
+ set diversity-factor and channel below.
+
+.. cfgcmd:: set protocols babel parameters diversity-factor <1-256>
+
+ This command sets the multiplicative factor used for diversity routing,
+ in units of 1/256; lower values cause diversity to play a more important role
+ in route selection.
+ The default it 256, which means that diversity plays no role in route
+ selection; you will probably want to set that to 128 or less on nodes
+ with multiple independent radios.
+
+.. cfgcmd:: set protocols babel parameters resend-delay <milliseconds>
+
+ This command specifies the time in milliseconds after which an 'important'
+ request or update will be resent. The default is 2000 ms.
+
+.. cfgcmd:: set protocols babel parameters smoothing-half-life <seconds>
+
+ This command specifies the time constant, in seconds, of the smoothing
+ algorithm used for implementing hysteresis.
+ Larger values reduce route oscillation at the cost of very slightly increasing
+ convergence time. The value 0 disables hysteresis, and is suitable for wired
+ networks. The default is 4 s.
+
+Interfaces Configuration
+------------------------
+
+.. cfgcmd:: set protocols babel interface <interface> type <auto|wired|wireless>
+
+ This command sets the interface type:
+
+ **auto** – automatically determines the interface type.
+ **wired** – enables optimisations for wired interfaces.
+ **wireless** – disables a number of optimisations that are only correct
+ on wired interfaces. Specifying wireless is always correct,
+ but may cause slower convergence and extra routing traffic.
+
+.. cfgcmd:: set protocols babel interface <interface> split-horizon <default|disable|enable>
+
+ This command specifies whether to perform split-horizon on the interface.
+ Specifying no babel split-horizon is always correct, while babel split-horizon
+ is an optimisation that should only be used on symmetric
+ and transitive (wired) networks.
+
+ **default** – enable split-horizon on wired interfaces, and disable
+ split-horizon on wireless interfaces.
+ **enable** – enable split-horizon on this interfaces.
+ **disable** – disable split-horizon on this interfaces.
+
+.. cfgcmd:: set protocols babel interface <interface> hello-interval <milliseconds>
+
+ This command specifies the time in milliseconds between two scheduled hellos.
+ On wired links, Babel notices a link failure within two hello intervals;
+ on wireless links, the link quality value is reestimated at every hello
+ interval.
+ The default is 4000 ms.
+
+.. cfgcmd:: set protocols babel interface <interface> update-interval <milliseconds>
+
+ This command specifies the time in milliseconds between two scheduled updates.
+ Since Babel makes extensive use of triggered updates,
+ this can be set to fairly high values on links with little packet loss.
+ The default is 20000 ms.
+
+.. cfgcmd:: set protocols babel interface <interface> rxcost <1-65534>
+
+ This command specifies the base receive cost for this interface.
+ For wireless interfaces, it specifies the multiplier used for computing
+ the ETX reception cost (default 256);
+ for wired interfaces, it specifies the cost that will be advertised to
+ neighbours.
+
+.. cfgcmd:: set protocols babel interface <interface> rtt-decay <1-256>
+
+ This command specifies the decay factor for the exponential moving average
+ of RTT samples, in units of 1/256.
+ Higher values discard old samples faster. The default is 42.
+
+.. cfgcmd:: set protocols babel interface <interface> rtt-min <milliseconds>
+
+ This command specifies the minimum RTT, in milliseconds,
+ starting from which we increase the cost to a neighbour.
+ The additional cost is linear in (rtt - rtt-min). The default is 10 ms.
+
+.. cfgcmd:: set protocols babel interface <interface> rtt-max <milliseconds>
+
+ This command specifies the maximum RTT, in milliseconds, above which
+ we don't increase the cost to a neighbour. The default is 120 ms.
+
+
+.. cfgcmd:: set protocols babel interface <interface> max-rtt-penalty <milliseconds>
+
+ This command specifies the maximum cost added to a neighbour because of RTT,
+ i.e. when the RTT is higher or equal than rtt-max.
+ The default is 150.
+ Setting it to 0 effectively disables the use of a RTT-based cost.
+
+.. cfgcmd:: set protocols babel interface <interface> enable-timestamps
+
+ This command enables sending timestamps with each Hello and IHU message
+ in order to compute RTT values.
+ It is recommended to enable timestamps on tunnel interfaces.
+
+.. cfgcmd:: set protocols babel interface <interface> channel <1-254|interfering|noninterfering>
+
+ This command set the channel number that diversity routing uses for this
+ interface (see diversity option above).
+
+ **1-254** – interfaces with a channel number interfere with
+ interfering interfaces and interfaces with the same channel number.
+ **interfering** – interfering interfaces are assumed to interfere with all other channels except
+ noninterfering channels.
+ **noninterfering** – noninterfering interfaces are assumed to only interfere
+ with themselves.
+
+Redistribution Configuration
+----------------------------
+
+.. cfgcmd:: set protocols babel redistribute <ipv4|ipv6> <route source>
+
+ This command redistributes routing information from the given route source
+ to the Babel process.
+
+ IPv4 route source: bgp, connected, eigrp, isis, kernel, nhrp, ospf, rip, static.
+
+ IPv6 route source: bgp, connected, eigrp, isis, kernel, nhrp, ospfv3, ripng, static.
+
+.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> access-list <in|out> <number>
+
+ This command can be used to filter the Babel routes using access lists.
+ :cfgcmd:`in` and :cfgcmd:`out` this is the direction in which the access
+ lists are applied.
+
+.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> interface <interface> access-list <in|out> <number>
+
+ This command allows you apply access lists to a chosen interface to
+ filter the Babel routes.
+
+.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> prefix-list <in|out> <name>
+
+ This command can be used to filter the Babel routes using prefix lists.
+ :cfgcmd:`in` and :cfgcmd:`out` this is the direction in which the prefix
+ lists are applied.
+
+.. cfgcmd:: set protocols babel distribute-list <ipv4|ipv6> interface <interface> prefix-list <in|out> <name>
+
+ This command allows you apply prefix lists to a chosen interface to
+ filter the Babel routes.
+
+Configuration Example
+---------------------
+
+Simple Babel configuration using 2 nodes and redistributing connected interfaces.
+
+**Node 1:**
+
+.. code-block:: none
+
+ set interfaces loopback lo address 10.1.1.1/32
+ set interfaces loopback lo address fd12:3456:dead:beef::1/128
+ set protocols babel interface eth0 type wired
+ set protocols babel redistribute ipv4 connected
+ set protocols babel redistribute ipv6 connected
+
+**Node 2:**
+
+.. code-block:: none
+
+ set interfaces loopback lo address 10.2.2.2/32
+ set interfaces loopback lo address fd12:3456:beef:dead::2/128
+ set protocols babel interface eth0 type wired
+ set protocols babel redistribute ipv4 connected
+ set protocols babel redistribute ipv6 connected