Nanostack Border Router

Nanostack Border Router is a generic Mbed border router implementation that provides the 6LoWPAN ND or Wi-SUN border router initialization logic. Pelion Device Management enabled border router for Wi-SUN can be found from repository https://github.com/PelionIoT/pelion-border-router.

A border router is a network gateway between a wireless 6LoWPAN mesh network and a backhaul network. It controls and relays traffic between the two networks. In a typical setup, a 6LoWPAN border router is connected to another router in the backhaul network (over Ethernet, Cellular or a serial line) which in turn forwards traffic to and from the internet or a private company LAN, for instance.

Structure

This application runs on Mbed OS and uses PHY drivers and Nanostack to form a border router.

The code layout is organized like this:

configs/                  Contains example configuration files
drivers/                  Contains PHY drivers
mbed-os/                  Contains Mbed OS, itself
source/                   Contains the application code
mbed_app.json             Build time configuration file

Building

1. Clone this repository.
2. Run mbed deploy.
3. Add connectivity driver, if not provided by Mbed OS.
4. Select target platform.
5. Select toolchain.
6. Configure.
7. Build.

For example:

$ mbed deploy

$ mbed target K64F
 OR
$ mbed target DISCO_F769NI

$ mbed toolchain GCC_ARM

$ mbed compile

Adding connectivity driver

This application requires the 802.15.4 RF driver to be provided for the networking stack. The driver can be either external, or provided by Mbed OS.

You can add an external driver by calling:

mbed add <driver>

For example, STM Spirit1 RF driver is added by calling mbed add stm-spirit1-rf-driver

Selecting the target platform

The target platform is the hardware on which the border router runs. There are target platforms already available in Mbed OS.

To write your own target, follow the instructions in Adding target support to Mbed OS 5.

The border router requires an RF driver to be provided for Nanostack. Currently, there are the following drivers available in the Mbed OS:

• Atmel AT86RF233.
• Atmel AT86RF212B.
• NXP MCR20A.
• STM-s2lp.

Following external driver can be added as described above:

• STM Spirit1.

The backhaul is either SLIP, Ethernet or Cellular. For Ethernet either an Mbed OS "EMAC" driver can be used, or a native Nanostack driver. Currently, native Nanostack drivers exists for the following backhauls:

• K64F Ethernet.
• SLIP driver.

The existing drivers are in the drivers/ folder. More drivers can be linked in.

See Notes on different hardware to see known combinations that work.

Configuring Nanostack Border Router

Applications using Nanostack Border Router need to use a .json file for the configuration. You can find the example configurations in the configs/ folder.

The backhaul configuration options

6LoWPAN ND border router options

To learn more about 6LoWPAN and the configuration parameters, please read the 6LoWPAN overview.

See configs/6lowpan_Atmel_RF.json for an example configuration file.

The routing protocol RPL (6LoWPAN ND)

Nanostack Border Router uses RPL as the routing protocol on the mesh network side (RF interface) when in 6LoWPAN-ND mode. Currently, only the grounded/non-storing operation mode is supported.

Nanostack Border Router offers the following configuration options for RPL:

Wi-SUN configuration

The Wi-SUN specific parameters are listed below.

Regulatory domain, operating class and operating mode are defined in the Wi-SUN PHY-specification.

Note: The configuration examples are for testing purposes only; do not use them for production or expose them.

Backhaul connectivity

The Nanostack border router application can be connected to a backhaul network. This enables you to connect the devices in a 6LoWPAN mesh network to the internet or a private LAN. The application supports SLIP (IPv6 encapsulation over a serial line), Ethernet and Cellular backhaul connectivity:

"config": {
    "backhaul-driver": {
        "help": "options are ETH, SLIP, EMAC, CELL",
        "value": "EMAC"
    },
    "backhaul-mac-src": {
        "help": "Where to get EUI48 address. Options are BOARD, CONFIG",
        "value": "BOARD"
    },
    "backhaul-mac": "{0x02, 0x00, 0x00, 0x00, 0x00, 0x01}",
    "backhaul-dynamic-bootstrap": true,
    "backhaul-prefix": "\"fd00:300::\"",
    "backhaul-next-hop": "\"fe80::1\"",
    "backhaul-default-route": "\"::/0\"",
    .............
}

You can select your preferred option through the configuration file (field backhaul-driver in the config section). The value SLIP includes the SLIP driver, and the value ETH compiles the border router application with Nanostack native Ethernet backhaul support. EMAC uses the board's default Mbed OS network driver, which must be EMAC-based (derived from EMACInterface). CELL uses the boards's default Mbed OS cellular device or external cellular device that is configured to provide the default cellular device.

You can define the MAC address on the backhaul interface manually (field backhaul-mac-src value CONFIG). Alternatively, you can use the MAC address provided by the development board (field backhaul-mac-src value BOARD). By default, the backhaul driver is set to EMAC and the MAC address source is BOARD.

You can also set the backhaul bootstrap mode (field backhaul-dynamic-bootstrap). By default, the bootstrap mode is set to true, which means the autonomous mode. With the autonomous mode, the border router learns the prefix information automatically from an IPv6 gateway in the Ethernet/SLIP segment. When the parameter is set to false, it enables you to set up a manual configuration of backhaul-prefix and backhaul-default-route.

If you use the static bootstrap mode, you need to configure a default route on the backhaul interface to properly forward packets between the backhaul and the 6LoWPAN mesh network. In addition to this, you need to set a backhaul prefix. The static mode creates a site-local IPv6 network from which packets cannot be routed outside.

When using the autonomous mode in the 6LoWPAN ND configuration, you can set the prefix-from-backhaul option to true to use the same backhaul prefix on the mesh network side as well. This allows the mesh nodes to be directly connectable from the outside of the mesh network.

For CELL backhaul, no configuration options for addresses are provided. Cellular backhaul device works always in autonomous mode and the border router learns the IPv6 prefix information from the cellular access.

Note on the SLIP backhaul driver

If you are using a K64F board, use the UART1 serial line of the board with the SLIP driver. See the pins section in the mbed_app.json configuration file. To use a different UART line, replace the SERIAL_TX and SERIAL_RX values with correct TX/RX pin names.

To use the hardware flow control, set the configuration field slip_hw_flow_control to true. By default, it is set to false. Before using hardware flow control, make sure the other end of your SLIP interface can handle the flow control.

For the pin names of your desired UART line, refer to your development board's documentation.

An example configuration for the SLIP driver:

"target_overrides": {
    "K64F": {
        "SERIAL_TX": "PTE0",
        "SERIAL_RX": "PTE1",
        "SERIAL_CTS": "PTE2",
        "SERIAL_RTS": "PTE3"
    }

Note on EMAC backhaul

When backhaul_driver is set to EMAC, the border router uses the target's default network driver, as supplied by NetworkInterface::get_default_instance. This must be EMAC-based, derived from EMACInterface. If it is the same driver that a default-constructed EthernetInterface would use, so in principle it should work on any board where EthernetInterface works.

To use a different interface, change the setting of target.default-network-interface-type in mbed_app.json to point to a different interface type, or add an overriding definition of NetworkInterface::get_default_instance to the application - this overrides any default supplied by the target board.

To use Wi-Fi or other more complex EMAC drivers, necessary configuration parameters must be supplied, either using mbed_app.json or configuration in the NetworkInterface::get_default_instance override. Also, the driver must follow the guidelines of EMACInterface - the border router does not call the EMACInterface's connect method, so the driver must work with only a powerup call to the EMAC.

Note on CELL backhaul

When backhaul_driver is set to CELL, the border router will use the target's default cellular device, as supplied by CellularInterface::get_default_instance. Cellular device must support IPv6 PPP connection mode. Board must supply the default Mbed OS cellular device or there must be an external cellular device that is configured to provide default cellular device to Mbed OS.

Switching the RF shield

By default, the application uses an Atmel AT86RF233/212B RF driver. You can alternatively use any RF driver provided in the drivers/ folder or link in your own driver. You can set the configuration for the RF driver in the json file.

To select the Atmel radio shield, use:

        "radio-type":{
            "help": "options are ATMEL, MCR20, SPIRIT1, S2LP",
            "value": "ATMEL"
        },

To select the NXP radio shield, use:

        "radio-type":{
            "help": "options are ATMEL, MCR20, SPIRIT1, S2LP",
            "value": "MCR20"
        },

To select the STM Spirit1 radio shield, use:

        "radio-type":{
            "help": "options are ATMEL, MCR20, SPIRIT1, S2LP",
            "value": "SPIRIT1"
        },

To select the STM S2LP radio shield, use:

        "radio-type":{
            "help": "options are ATMEL, MCR20, SPIRIT1, S2LP",
            "value": "S2LP"
        },

If you have chosen the STM Spirit1 Sub-1 GHz RF expansion board X-NUCLEO-IDS01A4, you need to configure its MAC address in the mbed_app.json file. For example:

    "target_overrides": {
        "*": {
            "spirit1.mac-address": "{0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7}"
        },
    }

Note: This MAC address must be unique within the 6LoWPAN mesh network.

After changing the radio shield, recompile the application.

Wi-SUN RF shield

Currently, only one radio shield, the STM S2LP radio shield, supports Wi-SUN.

Wi-SUN test configurations

You can set the Border Router to fixed-channel mode by setting the channel function to fixed-channel, by defining the channel number and by setting the broadcast intervals:

        "uc-channel-function": 0,
        "bc-channel-function": 0, 
        "uc-fixed-channel": 11,
        "bc-fixed-channel": 11,
        "bc-dwell-interval": 255,
        "bc-interval": 1020,

You can set the EAPOL group transient key (GTK) to a predefined value by setting the GTK0:

        "GTK0": "{0xBB, 0x06, 0x08, 0x57, 0x2C, 0xE1, 0x4D, 0x7B, 0xA2, 0xD1, 0x55, 0x49, 0x9C, 0xC8, 0x51, 0x9B}",

For the predefined GTK, the Wireshark IEEE 802.15.4 network decryption key can be calculated using SHA-256('Network name' || GTK0).

File system support

The application can use the file system as instructed in Mbed OS storage documentation. The file system is not enabled by default due to a variety of possible configurations.

File system activation happens by telling the file system the root path to Nanostack. To set the root path, use the function:

ns_file_system_set_root_path(root-path)

After you have set the root path, Wi-SUN stack reads the configuration settings from the file system. Wi-SUN stack writes the configuration back to the file system after the configuration changes.

Running the border router application

1. Find the binary file nanostack-border-router.bin in the BUILD folder.
2. Copy the binary to the USB mass storage root of the development board. It is automatically flashed to the target MCU. When the flashing is complete, the board restarts itself. Press the Reset button of the development board if it does not restart automatically.
3. The program begins execution.
4. Open the serial connection, for example PuTTY.

Serial connection settings

Serial connection settings for the Nanorouter are as follows:

• Baud-rate = 115200.
• Data bits = 8.
• Stop bits = 1.

If there is no input from the serial terminal, press the Reset button of the development board.

In the PuTTY main screen, save the session, and click Open. This opens a console window showing debug messages from the application. If the console screen is blank, you may need to press the Reset button of the board to see the debug information. The serial output from the 6LoWPAN border router looks something like this in the console:

[INFO][app ]: Starting Nanostack border router...
[INFO][brro]: NET_IPV6_BOOTSTRAP_AUTONOMOUS
[INFO][app ]: Using ETH backhaul driver...
[INFO][Eth ]: Ethernet cable is connected.
[INFO][addr]: Tentative Address added to IF 1: fe80::ac41:dcff:fe37:72c4
[INFO][addr]: DAD passed on IF 1: fe80::ac41:dcff:fe37:72c4
[INFO][addr]: Tentative Address added to IF 1: 2001:999:21:9ce:ac41:dcff:fe37:72c4
[INFO][addr]: DAD passed on IF 1: 2001:999:21:9ce:ac41:dcff:fe37:72c4
[INFO][brro]: Backhaul bootstrap ready, IPv6 = 2001:999:21:9ce:ac41:dcff:fe37:72c4
[INFO][brro]: Backhaul interface addresses:
[INFO][brro]:    [0] fe80::ac41:dcff:fe37:72c4
[INFO][brro]:    [1] 2001:999:21:9ce:ac41:dcff:fe37:72c4
[INFO][addr]: Address added to IF 0: fe80::ff:fe00:face
[INFO][br  ]: BR nwk base ready for start
[INFO][br  ]: Refresh Contexts
[INFO][br  ]: Refresh Prefixs
[INFO][addr]: Address added to IF 0: 2001:999:21:9ce:0:ff:fe00:face
[INFO][addr]: Address added to IF 0: fe80::fec2:3d00:4:a0cd
[INFO][brro]: RF bootstrap ready, IPv6 = 2001:999:21:9ce:0:ff:fe00:face
[INFO][brro]: RF interface addresses:
[INFO][brro]:    [0] fe80::ff:fe00:face
[INFO][brro]:    [1] fe80::fec2:3d00:4:a0cd
[INFO][brro]:    [2] 2001:999:21:9ce:0:ff:fe00:face
[INFO][brro]: 6LoWPAN Border Router Bootstrap Complete.

Known Issues

• RF shield is using Serial Peripheral Interface (SPI) for communication. Some NUCLEO boards (like NUCLEO_F429ZI) may have a pin conflict when SPI is used.

License and contributions

The software is provided under Apache-2.0 license. Contributions to this project are accepted under the same license. Please see contributing.md for more info.

This project contains code from other projects. The original license text is included in those source files. They must comply with our license guide.