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# Configuring Interfaces

Reticulum supports using many kinds of devices as networking interfaces, and allows you to mix and match them in any way you choose. The number of distinct network topologies you can create with Reticulum is more or less endless, but common to them all is that you will need to define one or more interfaces for Reticulum to use.

The following sections describe the interfaces currently available in Reticulum, and gives example configurations for the respective interface types.

For a high-level overview of how networks can be formed over different interface types, have a look at the Building Networks chapter of this manual.

## Auto Interface

The Auto Interface enables communication with other discoverable Reticulum nodes over autoconfigured IPv6 and UDP. It does not need any functional IP infrastructure like routers or DHCP servers, but will require at least some sort of switching medium between peers (a wired switch, a hub, a WiFi access point or similar), and that link-local IPv6 is enabled in your operating system, which should be enabled by default in almost all OSes.

    # This example demonstrates a TCP server interface.
    # It will listen for incoming connections on the
    # specified IP address and port number.

    [[Default Interface]]
      type = AutoInterface
      interface_enabled = True

      # You can create multiple isolated Reticulum
      # networks on the same physical LAN by
      # specifying different Group IDs.

      group_id = reticulum

      # You can also select specifically which
      # kernel networking devices to use.

      devices = wlan0,eth1

      # Or let AutoInterface use all suitable
      # devices except for a list of ignored ones.

      ignored_devices = tun0,eth0

If you are connected to the Internet with IPv6, and your provider will route IPv6 multicast, you can potentially configure the Auto Interface to globally autodiscover other Reticulum nodes within your selected Group ID. You can specify the discovery scope by setting it to one of `link`, `admin`, `site`, `organisation` or `global`.

    [[Default Interface]]
      type = AutoInterface
      interface_enabled = True

      # Configure global discovery

      group_id = custom_network_name
      discovery_scope = global

      # Other configuration options

      discovery_port = 48555
      data_port = 49555

## I2P Interface

The I2P interface lets you connect Reticulum instances over the Invisible Internet Protocol. This can be especially useful in cases where you want to host a globally reachable Reticulum instance, but do not have access to any public IP addresses, have a frequently changing IP address, or have firewalls blocking inbound traffic.

Using the I2P interface, you will get a globally reachable, portable and persistent I2P address that your Reticulum instance can be reached at.

To use the I2P interface, you must have an I2P router running on your system. The easiest way to achieve this is to download and install the latest release of the `i2pd` package. For more details about I2P, see the geti2p.net website.

When an I2P router is running on your system, you can simply add an I2P interface to Reticulum:

    [[I2P]]
      type = I2PInterface
      interface_enabled = yes
      connectable = yes

On the first start, Reticulum will generate a new I2P address for the interface and start listening for inbound traffic on it. This can take a while the first time, especially if your I2P router was also just started, and is not yet well-connected to the I2P network. When ready, you should see I2P base32 address printed to your log file. You can also inspect the status of the interface using the `rnstatus` utility.

To connect to other Reticulum instances over I2P, just add a comma-separated list of I2P base32 addresses to the `peers` option of the interface:

    [[I2P]]
      type = I2PInterface
      interface_enabled = yes
      connectable = yes
      peers = 5urvjicpzi7q3ybztsef4i5ow2aq4soktfj7zedz53s47r54jnqq.b32.i2p

It can take anywhere from a few seconds to a few minutes to establish I2P connections to the desired peers, so Reticulum handles the process in the background, and will output relevant events to the log.

Please Note! While the I2P interface is the simplest way to use Reticulum over I2P, it is also possible to tunnel the TCP server and client interfaces over I2P manually. This can be useful in situations where more control is needed, but requires manual tunnel setup through the I2P daemon configuration.

It is important to note that the two methods are interchangably compatible. You can use the I2PInterface to connect to a TCPServerInterface that was manually tunneled over I2P, for example. This offers a high degree of flexibility in network setup, while retaining ease of use in simpler use-cases.

## TCP Server Interface

The TCP Server interface is suitable for allowing other peers to connect over the Internet or private IP networks. When a TCP server interface has been configured, other Reticulum peers can connect to it with a TCP Client interface.

    # This example demonstrates a TCP server interface.
    # It will listen for incoming connections on the
    # specified IP address and port number.

    [[TCP Server Interface]]
      type = TCPServerInterface
      interface_enabled = True

      # This configuration will listen on all IP
      # interfaces on port 4242

      listen_ip = 0.0.0.0
      listen_port = 4242

      # Alternatively you can bind to a specific IP

      # listen_ip = 10.0.0.88
      # listen_port = 4242

      # Or a specific network device

      # device = eth0
      # port = 4242

Please Note! The TCP interfaces support tunneling over I2P, but to do so reliably, you must use the i2p_tunneled option:

    [[TCP Server on I2P]]
        type = TCPServerInterface
        interface_enabled = yes
        listen_ip = 127.0.0.1
        listen_port = 5001
        i2p_tunneled = yes

In almost all cases, it is easier to use the dedicated `I2PInterface`, but for complete control, and using I2P routers running on external systems, this option also exists.

## TCP Client Interface

To connect to a TCP server interface, you would naturally use the TCP client interface. Many TCP Client interfaces from different peers can connect to the same TCP Server interface at the same time.

The TCP interface types can also tolerate intermittency in the IP link layer. This means that Reticulum will gracefully handle IP links that go up and down, and restore connectivity after a failure, once the other end of a TCP interface reappears.

    # Here's an example of a TCP Client interface. The
    # target_host can either be an IP address or a hostname.

    [[TCP Client Interface]]
      type = TCPClientInterface
      interface_enabled = True
      target_host = 127.0.0.1
      target_port = 4242

It is also possible to use this interface type to connect via other programs or hardware devices that expose a KISS interface on a TCP port, for example software-based soundmodems. To do this, use the `kiss_framing` option:

    # Here's an example of a TCP Client interface that connects
    # to a software TNC soundmodem on a KISS over TCP port.

    [[TCP KISS Interface]]
      type = TCPClientInterface
      interface_enabled = True
      kiss_framing = True
      target_host = 127.0.0.1
      target_port = 8001

Caution! Only use the KISS framing option when connecting to external devices and programs like soundmodems and similar over TCP. When using the `TCPClientInterface` in conjunction with the `TCPServerInterface` you should never enable `kiss_framing`, since this will disable internal reliability and recovery mechanisms that greatly improves performance over unreliable and intermittent TCP links.

Please Note! The TCP interfaces support tunneling over I2P, but to do so reliably, you must use the i2p_tunneled option:

    [[TCP Client over I2P]]
        type = TCPClientInterface
        interface_enabled = yes
        target_host = 127.0.0.1
        target_port = 5001
        i2p_tunneled = yes

## UDP Interface

A UDP interface can be useful for communicating over IP networks, both private and the internet. It can also allow broadcast communication over IP networks, so it can provide an easy way to enable connectivity with all other peers on a local area network.

Please Note! Using broadcast UDP traffic has performance implications, especially on WiFi. If your goal is simply to enable easy communication with all peers in your local Ethernet broadcast domain, the Auto Interface performs better, and is even easier to use.

    # This example enables communication with other
    # local Reticulum peers over UDP.

    [[UDP Interface]]
      type = UDPInterface
      interface_enabled = True

      listen_ip = 0.0.0.0
      listen_port = 4242
      forward_ip = 255.255.255.255
      forward_port = 4242

      # The above configuration will allow communication
      # within the local broadcast domains of all local
      # IP interfaces.

      # Instead of specifying listen_ip, listen_port,
      # forward_ip and forward_port, you can also bind
      # to a specific network device like below.

      # device = eth0
      # port = 4242

      # Assuming the eth0 device has the address
      # 10.55.0.72/24, the above configuration would
      # be equivalent to the following manual setup.
      # Note that we are both listening and forwarding to
      # the broadcast address of the network segments.

      # listen_ip = 10.55.0.255
      # listen_port = 4242
      # forward_ip = 10.55.0.255
      # forward_port = 4242

      # You can of course also communicate only with
      # a single IP address

      # listen_ip = 10.55.0.15
      # listen_port = 4242
      # forward_ip = 10.55.0.16
      # forward_port = 4242

## RNode LoRa Interface

To use Reticulum over LoRa, the RNode interface can be used, and offers full control over LoRa parameters.

    # Here's an example of how to add a LoRa interface
    # using the RNode LoRa transceiver.

    [[RNode LoRa Interface]]
      type = RNodeInterface

      # Enable interface if you want use it!
      interface_enabled = True

      # Serial port for the device
      port = /dev/ttyUSB0

      # Set frequency to 867.2 MHz
      frequency = 867200000

      # Set LoRa bandwidth to 125 KHz
      bandwidth = 125000

      # Set TX power to 7 dBm (5 mW)
      txpower = 7

      # Select spreading factor 8. Valid
      # range is 7 through 12, with 7
      # being the fastest and 12 having
      # the longest range.
      spreadingfactor = 8

      # Select coding rate 5. Valid range
      # is 5 throough 8, with 5 being the
      # fastest, and 8 the longest range.
      codingrate = 5

      # You can configure the RNode to send
      # out identification on the channel with
      # a set interval by configuring the
      # following two parameters.

      # id_callsign = MYCALL-0
      # id_interval = 600

      # For certain homebrew RNode interfaces
      # with low amounts of RAM, using packet
      # flow control can be useful. By default
      # it is disabled.

      # flow_control = False

      # It is possible to limit the airtime
      # utilisation of an RNode by using the
      # following two configuration options.
      # The short-term limit is applied in a
      # window of approximately 15 seconds,
      # and the long-term limit is enforced
      # over a rolling 60 minute window. Both
      # options are specified in percent.

      # airtime_limit_long = 1.5
      # airtime_limit_short = 33

## Serial Interface

Reticulum can be used over serial ports directly, or over any device with a serial port, that will transparently pass data. Useful for communicating directly over a wire-pair, or for using devices such as data radios and lasers.

    [[Serial Interface]]
      type = SerialInterface
      interface_enabled = True

      # Serial port for the device
      port = /dev/ttyUSB0

      # Set the serial baud-rate and other
      # configuration parameters.
      speed = 115200
      databits = 8
      parity = none
      stopbits = 1

## Pipe Interface

Using this interface, Reticulum can use any program as an interface via stdin and stdout. This can be used to easily create virtual interfaces, or to interface with custom hardware or other systems.

    [[Pipe Interface]]
      type = PipeInterface
      interface_enabled = True

      # External command to execute
      command = netcat -l 5757

      # Optional respawn delay, in seconds
      respawn_delay = 5

Reticulum will write all packets to stdin of the `command` option, and will continuously read and scan its stdout for Reticulum packets. If `EOF` is reached, Reticulum will try to respawn the program after waiting for `respawn_interval` seconds.

## KISS Interface

With the KISS interface, you can use Reticulum over a variety of packet radio modems and TNCs, including OpenModem. KISS interfaces can also be configured to periodically send out beacons for station identification purposes.

    [[Packet Radio KISS Interface]]
      type = KISSInterface
      interface_enabled = True

      # Serial port for the device
      port = /dev/ttyUSB1

      # Set the serial baud-rate and other
      # configuration parameters.
      speed = 115200
      databits = 8
      parity = none
      stopbits = 1

      # Set the modem preamble.
      preamble = 150

      # Set the modem TX tail.
      txtail = 10

      # Configure CDMA parameters. These
      # settings are reasonable defaults.
      persistence = 200
      slottime = 20

      # You can configure the interface to send
      # out identification on the channel with
      # a set interval by configuring the
      # following two parameters. The KISS
      # interface will only ID if the set
      # interval has elapsed since it's last
      # actual transmission. The interval is
      # configured in seconds.
      # This option is commented out and not
      # used by default.
      # id_callsign = MYCALL-0
      # id_interval = 600

      # Whether to use KISS flow-control.
      # This is useful for modems that have
      # a small internal packet buffer, but
      # support packet flow control instead.
      flow_control = false

## AX.25 KISS Interface

If you’re using Reticulum on amateur radio spectrum, you might want to use the AX.25 KISS interface. This way, Reticulum will automatically encapsulate it’s traffic in AX.25 and also identify your stations transmissions with your callsign and SSID.

Only do this if you really need to! Reticulum doesn’t need the AX.25 layer for anything, and it incurs extra overhead on every packet to encapsulate in AX.25.

A more efficient way is to use the plain KISS interface with the beaconing functionality described above.

    [[Packet Radio AX.25 KISS Interface]]
      type = AX25KISSInterface

      # Set the station callsign and SSID
      callsign = NO1CLL
      ssid = 0

      # Enable interface if you want use it!
      interface_enabled = True

      # Serial port for the device
      port = /dev/ttyUSB2

      # Set the serial baud-rate and other
      # configuration parameters.
      speed = 115200
      databits = 8
      parity = none
      stopbits = 1

      # Set the modem preamble. A 150ms
      # preamble should be a reasonable
      # default, but may need to be
      # increased for radios with slow-
      # opening squelch and long TX/RX
      # turnaround
      preamble = 150

      # Set the modem TX tail. In most
      # cases this should be kept as low
      # as possible to not waste airtime.
      txtail = 10

      # Configure CDMA parameters. These
      # settings are reasonable defaults.
      persistence = 200
      slottime = 20

      # Whether to use KISS flow-control.
      # This is useful for modems with a
      # small internal packet buffer.
      flow_control = false

## Common Interface Options

A number of general configuration options are available on most interfaces. These can be used to control various aspects of interface behaviour.

> - The `enabled` option tells Reticulum whether or not to bring up the interface. Defaults to `False`. For any interface to be brought up, the `enabled` option must be set to `True` or `Yes`.
> - The `mode` option allows selecting the high-level behaviour of the interface from a number of options.

>   > - The default value is `full`. In this mode, all discovery, meshing and transport functionality is available.

>   > - In the `access_point` (or shorthand `ap`) mode, the interface will operate as a network access point. In this mode, announces will not be automatically broadcasted on the interface, and paths to destinations on the interface will have a much shorter expiry time. This mode is useful for creating interfaces that are mostly quiet, unless when someone is actually using them. An example of this could be a radio interface serving a wide area, where users are expected to connect momentarily, use the network, and then disappear again.

> - The `outgoing` option sets whether an interface is allowed to transmit. Defaults to `True`. If set to `False` or `No` the interface will only receive data, and never transmit.
> - The `network_name` option sets the virtual network name for the interface. This allows multiple separate network segments to exist on the same physical channel or medium.
> - The `passphrase` option sets an authentication passphrase on the interface. This option can be used in conjunction with the `network_name` option, or be used alone.
> - The `ifac_size` option allows customising the length of the Interface Authentication Codes carried by each packet on named and/or authenticated network segments. It is set by default to a size suitable for the interface in question, but can be set to a custom size between 8 and 512 bits by using this option. In normal usage, this option should not be changed from the default.
> - The `announce_cap` option lets you configure the maximum bandwidth to allocate, at any given time, to propagating announces and other network upkeep traffic. It is configured at 2% by default, and should normally not need to be changed. Can be set to any value between `1` and `100`.

>   > If an interface exceeds its announce cap, it will queue announces for later transmission. Reticulum will always prioritise propagating announces from nearby nodes first. This ensures that the local topology is prioritised, and that slow networks are not overwhelmed by interconnected fast networks.

>   > Destinations that are rapidly re-announcing will be down-prioritised further. Trying to get “first-in-line” by announce spamming will have the exact opposite effect: Getting moved to the back of the queue every time a new announce from the excessively announcing destination is received.

>   > This means that it is always beneficial to select a balanced announce rate, and not announce more often than is actually necesarry for your application to function.

> - The `bitrate` option configures the interface bitrate. Reticulum will use interface speeds reported by hardware, or try to guess a suitable rate when the hardware doesn’t report any. In most cases, the automatically found rate should be sufficient, but it can be configured by using the `bitrate` option, to set the interface speed in bits per second.

## Interface Modes

The optional `mode` setting is available on all interfaces, and allows selecting the high-level behaviour of the interface from a number of modes. These modes affect how Reticulum selects paths in the network, how announces are propagated, how long paths are valid and how paths are discovered.

Configuring modes on interfaces is not strictly necessary, but can be useful when building or connecting to more complex networks. If your Reticulum instance is not running a Transport Node, it is rarely useful to configure interface modes, and in such cases interfaces should generally be left in the default mode.

> - The default mode is `full`. In this mode, all discovery, meshing and transport functionality is activated.
> - The `gateway` mode (or shorthand `gw`) also has all discovery, meshing and transport functionality available, but will additionally try to discover unknown paths on behalf of other nodes residing on the `gateway` interface. If Reticulum receives a path request for an unknown destination, from a node on a `gateway` interface, it will try to discover this path via all other active interfaces, and forward the discovered path to the requestor if one is found.
>   If you want to allow other nodes to widely resolve paths or connect to a network via an interface, it might be useful to put it in this mode. By creating a chain of `gateway` interfaces, other nodes will be able to immediately discover paths to any destination along the chain.
>   Please note! It is the interface facing the clients that must be put into `gateway` mode for this to work, not the interface facing the wider network (for this, the `boundary` mode can be useful, though).
> - In the `access_point` (or shorthand `ap`) mode, the interface will operate as a network access point. In this mode, announces will not be automatically broadcasted on the interface, and paths to destinations on the interface will have a much shorter expiry time. In addition, path requests from clients on the access point interface will be handled in the same way as the `gateway` interface.
>   This mode is useful for creating interfaces that remain quiet, until someone actually starts using them. An example of this could be a radio interface serving a wide area, where users are expected to connect momentarily, use the network, and then disappear again.
> - The `roaming` mode should be used on interfaces that are roaming (physically mobile), seen from the perspective of other nodes in the network. As an example, if a vehicle is equipped with an external LoRa interface, and an internal, WiFi-based interface, that serves devices that are moving with the vehicle, the external LoRa interface should be configured as `roaming`, and the internal interface can be left in the default mode. With transport enabled, such a setup will allow all internal devices to reach each other, and all other devices that are available on the LoRa side of the network, when they are in range. Devices on the LoRa side of the network will also be able to reach devices internal to the vehicle, when it is in range. Paths via `roaming` interfaces also expire faster.
> - The purpose of the `boundary` mode is to specify interfaces that establish connectivity with network segments that are significantly different than the one this node exists on. As an example, if a Reticulum instance is part of a LoRa-based network, but also has a high-speed connection to a public Transport Node available on the Internet, the interface connecting over the Internet should be set to `boundary` mode.

For a table describing the impact of all modes on announce propagation, please see the Announce Propagation Rules section.

## Announce Rate Control

The built-in announce control mechanisms and the default `announce_cap` option described above are sufficient most of the time, but in some cases, especially on fast interfaces, it may be useful to control the target announce rate. Using the `announce_rate_target`, `announce_rate_grace` and `announce_rate_penalty` options, this can be done on a per-interface basis, and moderates the rate at which received announces are re-broadcasted to other interfaces.

> - The `announce_rate_target` option sets the minimum amount of time, in seconds, that should pass between received announces, for any one destination. As an example, setting this value to `3600` means that announces received on this interface will only be re-transmitted and propagated to other interfaces once every hour, no matter how often they are received.
> - The optional `announce_rate_grace` defines the number of times a destination can violate the announce rate before the target rate is enforced.
> - The optional `announce_rate_penalty` configures an extra amount of time that is added to the normal rate target. As an example, if a penalty of `7200` seconds is defined, once the rate target is enforced, the destination in question will only have its announces propagated every 3 hours, until it lowers its actual announce rate to within the target.

These mechanisms, in conjunction with the `annouce_cap` mechanisms mentioned above means that it is essential to select a balanced announce strategy for your destinations. The more balanced you can make this decision, the easier it will be for your destinations to make it into slower networks that many hops away. Or you can prioritise only reaching high-capacity networks with more frequent announces.

Current statistics and information about announce rates can be viewed using the `rnpath -r` command.

It is important to note that there is no one right or wrong way to set up announce rates. Slower networks will naturally tend towards using less frequent announces to conserve bandwidth, while very fast networks can support applications that need very frequent announces. Reticulum implements these mechanisms to ensure that a large span of network types can seamlessly co-exist and interconnect.

## New Destination Rate Limiting

On public interfaces, where anyone may connect and announce new destinations, it can be useful to control the rate at which announces for new destinations are processed.

If a large influx of announces for newly created or previously unknown destinations occur within a short amount of time, Reticulum will place these announces on hold, so that announce traffic for known and previously established destinations can continue to be processed without interruptions.

After the burst subsides, and an additional waiting period has passed, the held announces will be released at a slow rate, until the hold queue is cleared. This also means, that should a node decide to connect to a public interface, announce a large amount of bogus destinations, and then disconnect, these destination will never make it into path tables and waste network bandwidth on retransmitted announces.

It’s important to note that the ingress control works at the level of individual sub-interfaces. As an example, this means that one client on a TCP Server Interface cannot disrupt processing of incoming announces for other connected clients on the same TCP Server Interface. All other clients on the same interface will still have new announces processed without interruption.

By default, Reticulum will handle this automatically, and ingress announce control will be enabled on interface where it is sensible to do so. It should generally not be neccessary to modify the ingress control configuration, but all the parameters are exposed for configuration if needed.

> - The `ingress_control` option tells Reticulum whether or not to enable announce ingress control on the interface. Defaults to `True`.
> - The `ic_new_time` option configures how long (in seconds) an interface is considered newly spawned. Defaults to `2*60*60` seconds. This option is useful on publicly accessible interfaces that spawn new sub-interfaces when a new client connects.
> - The `ic_burst_freq_new` option sets the maximum announce ingress frequency for newly spawned interfaces. Defaults to `3.5` announces per second.
> - The `ic_burst_freq` option sets the maximum announce ingress frequency for other interfaces. Defaults to `12` announces per second.

>   > If an interface exceeds its burst frequency, incoming announces for unknown destinations will be temporarily held in a queue, and not processed until later.

> - The `ic_max_held_announces` option sets the maximum amount of unique announces that will be held in the queue. Any additional unique announces will be dropped. Defaults to `256` announces.
> - The `ic_burst_hold` option sets how much time (in seconds) must pass after the burst frequency drops below its threshold, for the announce burst to be considered cleared. Defaults to `60` seconds.
> - The `ic_burst_penalty` option sets how much time (in seconds) must pass after the burst is considered cleared, before held announces can start being released from the queue. Defaults to `5*60` seconds.
> - The `ic_held_release_interval` option sets how much time (in seconds) must pass between releasing each held announce from the queue. Defaults to `30` seconds.