Physical RAN
---------------

We are now ready to replace the emulated RAN with physical gNBs and
real UEs. You will need to edit ``hosts.ini`` to reflect the Aether
cluster you want to support, where just a single server is sufficient
and there is no reason to include nodes in the ``[gnbsim_nodes]`` set.
We also assume you start with a variant of ``vars/main.yml``
customized for running physical 5G radios, which is easy to do:

.. code-block::

   $ cd vars
   $ cp main-gNB.yml main.yml

The following focuses on a single gNB, which we assume is connected to
the same L2 network as the Aether cluster. In our running example,
this implies both are on subnet ``10.76.28.0/24``.

.. admonition:: Troubleshooting Hint

  Physical gNBs connect to SD-Core (both the AMF in the control plane
  and the UPF in the user plane) in exactly the same way as external
  instances of gNBsim. Going through the process of bringing up gNBsim
  in a second server, as described in the previous section, is a good
  way to validate that your Core is "gNB-ready".


Modify Configuration
~~~~~~~~~~~~~~~~~~~~~~~~

Modify the ``core`` section of ``vars/main.yml`` to match the
following, substituting your local details for ``ens18`` and
``10.76.28.113``. Of particular note, setting ``ran_subnet`` to the
empty string indicates that the gNB is connected to the same physical
L2 network as your Aether cluster, and the new ``values_file`` is
tailored for a physical RAN rather than the emulated RAN we've been
using.

.. code-block::

   core:
       standalone: "true"
       data_iface: ens18
       values_file: "deps/5gc/roles/core/templates/radio-5g-values.yaml"
       ran_subnet: ""
       helm:
           chart_ref: aether/sd-core
           chart_version: 0.12.6
       upf:
           ip_prefix: "192.168.252.0/24"
       amf:
           ip: "10.76.28.113"


Prepare UEs
~~~~~~~~~~~~

When selecting UEs to connect to Aether, be aware that not all phones
support the CBRS frequency bands that Aether uses. For band n78,
Aether is known to work with recent iPhones (11 and greater), Google
Pixel phones (4 and greater), OnePlus phones, and Moto G 5G
phones. For band n48, Aether is known to work with Moto G 5G and
OnePlus phones; Pixel 7 phones are purported to work as well.  Another
option is to use a 5G dongle connected to a Raspberry Pi as a
demonstration UE. This makes it easier to run diagnostic tests from
the UE. For example, we have used `APAL's 5G dongle
<https://www.apaltec.com/dongle/>`__ with Aether.

5G-connected devices must have a SIM card, which you are responsible
for creating and inserting.  You will need a SIM card writer (these
are readily available for purchase on Amazon) and a PLMN identifier
constructed from a valid MCC/MNC pair. For our purposes, we use two
different PLMN ids: ``315010`` constructed from MCC=315 (US) and
MNC=010 (CBRS), and ``00101`` constructed from MCC=001 (TEST) and
MNC=01 (TEST). You should use whatever values are appropriate for your
local environment.  You then assign an IMSI and two secret keys to
each SIM card. Throughout this section, we use the following values as
exemplars:

* IMSI: each one is unique, matching pattern ``315010*********`` (up to 15 digits)
* OPc: ``69d5c2eb2e2e624750541d3bbc692ba5``
* Key: ``000102030405060708090a0b0c0d0e0f``

Note that the actual config files distributed with OnRamp have IMSIs
constructed using PLMN id ``00101``. Both sets of examples are taken
from working deployments (``315010`` for a 4G/eNB and ``00101`` for a
5G/gNB), so in principle either should work as a model you can emulate
in your deployment. As a practical matter, however, it is certainly
easiest (and safest) to start with the existing code.

After inserting the SIM card into the device and powering it up, log
into the phone, select ``Network Settings > SIMs`` and configure the
*Access Point Name (APN)* to be ``internet``. This value corresponds
to variable ``dnn`` (*Data Network Name*), as defined in
``deps/5gc/roles/core/templates/radio-5g-values.yaml``.

Finally, modify the ``subscribers`` block of the
``omec-sub-provision`` section in file
``deps/5gc/roles/core/templates/radio-5g-values.yaml`` to record the IMSI,
OPc, and Key values configured onto your SIM cards. The block also
defines a sequence number that is intended to thwart replay
attacks. For example, the following code block adds IMSIs between
``315010999912301`` and ``315010999912310``:

.. code-block::

   subscribers:
   - ueId-start: "315010999912301"
     ueId-end: "315010999912310"
     plmnId: "315010"
     opc: "69d5c2eb2e2e624750541d3bbc692ba5"
     key: "000102030405060708090a0b0c0d0e0f"
     sequenceNumber: 135

Further down in the same ``omec-sub-provision`` section you will find
two other blocks that also need to be edited. The first,
``device-groups``, assigns IMSIs to *Device Groups*. You will need to
reenter the individual IMSIs from the ``subscribers`` block that will
be part of the device-group:

.. code-block::

   device-groups:
   - name:  "5g-user-group1"
      imsis:
          - "315010999912301"
          - "315010999912302"
          - "315010999912303"

The second block, ``network-slices``, sets various parameters
associated with the *Slices* that connect device groups to
applications.  Here, you will need to reenter the PLMN information,
with the other slice parameters remaining unchanged (for now):

.. code-block::

   plmn:
       mcc: "315"
       mnc: "010"

Aether supports multiple *Device Groups* and *Slices*, but the data
entered here is purposely minimal; it's just enough to bring up and
debug the installation. Over the lifetime of a running system,
information about *Device Groups* and *Slices* (and the other
abstractions they build upon) should be entered via the ROC, as
described the section on Runtime Control. When you get to that point,
Ansible variable ``standalone`` in ``vars/main.yml`` (which
corresponds to the override value assigned to
``provision-network-slice`` in ``radio-5g-values.yaml``) should be set
to ``false``. Doing so causes the ``device-groups`` and
``network-slices`` blocks of ``radio-5g-values.yaml`` to be
ignored. The ``subscribers`` block is always required to configure
SD-Core.


Bring Up Aether
~~~~~~~~~~~~~~~~~~~~~

You are now ready to bring Aether on-line. We assume a fresh install
by typing the following:

.. code-block::

   $ make aether-k8s-install
   $ make aether-5gc-install

You can verify the installation by running ``kubectl`` just as you did
in earlier stages. Note that we postpone bringing up the AMP until
later so as to have fewer moving parts to debug.


gNodeB Setup
~~~~~~~~~~~~~~~~~~~~

Once the SD-Core is up and running, we are ready to bring up the
physical gNB. The details of how to do this depend on the specific
device you are using, but we identify the main issues you need to
address using SERCOMM's 5G femto cell (as distributed by MosoLabs) as
an example. That particular device uses either the n48 or n78 band and
is on the ONF MarketPlace, where you can also find a User's Guide that
gives detailed instructions about configuring the gNB.

.. _reading_sercomm:
.. admonition:: Further Reading

   `MOSO CANOPY 5G INDOOR SMALL CELL
   <https://opennetworking.org/products/moso-canopy-5g-indoor-small-cell/>`__.

.. admonition:: Troubleshooting Hint

  The product data sheet shows support for frequency bands
  n78/n48/n77, but individual devices do not necessarily support all
  three. For example, we have experience with an n78 device and an n48
  device, with the latter (n48) now becoming the default. For that
  band, PLMN id ``00101`` is currently recommended.

For the purposes of the following description, we assume the gNB is
assigned IP address ``10.76.28.187``, which per our running example,
is on the same L2 network as our Aether server (``10.76.28.113``).
:numref:`Figure %s <fig-sercomm>` shows a screenshot of the SERCOMM
gNB management dashboard, which we reference in the instructions that
follow:

.. _fig-sercomm:
.. figure:: figures/Sercomm.png
    :width: 500px
    :align: center

    Management dashboard on the Sercomm gNB, showing the dropdown
    ``Settings`` menu overlayed on the ``NR Cell Configuration`` page
    (which shows default radio settings).


1. **Connect to Management Interface.** Start by connecting a laptop
   directly to the LAN port on the small cell, pointing your laptop's
   web browser at the device's management page
   (``https://10.10.10.189``).  You will need to assign your laptop an
   IP address on the same subnet (e.g., ``10.10.10.100``).  Once
   connected, log in with the credentials provided by the vendor.

2. **Configure WAN.** Visit the ``Settings > WAN`` page to configure
   how the small cell connects to the Internet via its WAN port,
   either dynamically using DHCP or statically by setting the device's
   IP address (``10.76.28.187``) and default gateway (``10.76.28.1``).

3. **Access Remote Management.** Once on the Internet, it should be
   possible to reach the management dashboard without being directly
   connected to the LAN port (``https://10.76.28.187``).

4. **Connect GPS.** Connect the small cell's GPS antenna to the GPS
   port, and place the antenna so it has line-of-site to the sky
   (i.e., place it in a window). The ``Status`` page of the management
   dashboard should report its latitude, longitude, and fix time.

5. **Spectrum Access System.** One reason the radio needs GPS is so it
   can report its location to a Spectrum Access System (SAS), a
   requirement in the US to coordinate access to the CBRS Spectrum in
   the 3.5 GHz band. For example, the production deployment of Aether
   uses the `Google SAS portal
   <https://cloud.google.com/spectrum-access-system/docs/overview>`__,
   which the small cell can be configured to query periodically. To do
   so, visit the ``Settings > SAS`` page.  Acquiring the credentials
   needed to access the SAS requires you go through a certification
   process, but as a practical matter, it may be possible to test an
   isolated/low-power femto cell indoors before completing that
   process. Consult with your local network administrator.

6. **Configure Radio Parameters.** Visit the ``Settings > NR Cell
   Configuration`` page (shown in the figure) to set parameters that
   control the radio. It should be sufficient to use the default
   settings when getting started.

7. **Configure the PLMN.** Visit the ``Settings > 5GC`` page to set
   the PLMN identifier on the small cell (``00101``) to match the
   MCC/MNC values (``001`` / ``01`` ) specified in the Core.

8. **Connect to Aether Control Plane.** Also on the ``Settings > 5GC``
   page, define the AMF Address to be the IP address of your Aether
   server (e.g., ``10.76.28.113``). Aether's SD-Core is configured to
   expose the corresponding AMF via a well-known port, so the server's
   IP address is sufficient to establish connectivity. The ``Status``
   page of the management dashboard should confirm that control
   interface is established.

9. **Connect to Aether User Plane.** As described in an earlier
   section, the Aether User Plane (UPF) is running at IP address
   ``192.168.252.3``. Connecting to that address requires installing a
   route to subnet ``192.168.252.0/24``. How you install this route is
   device and site-dependent. If the small cell provides a means to
   install static routes, then a route to destination
   ``192.168.252.0/24`` via gateway ``10.76.28.113`` (the server
   hosting Aether) will work. If the small cell does not allow static
   routes (as is the case for the SERCOMM gNB), then ``10.76.28.113``
   can be installed as the default gateway, but doing so requires that
   your server also be configured to forward IP packets on to the
   Internet.

.. admonition:: Troubleshooting Hint

  For the SERCOMM gNB, if you elect to enable GPS, then ``Setting >
  Sync_Settings > Sync_Mode`` should be set to ``TIME``.  With GPS and
  PTP disabled, ``Setting > Sync_Settings > Sync_Mode`` should be set
  to ``FREE_RUNNING``.

.. admonition:: Troubleshooting Hint

  For the SERCOMM gNB, we recommend the following when the gNB's
  addresses is acquired via DHCP, assuming that address is unlikely to
  change. When configuring the WAN (via the LAN), start with DHCP
  enabled. Note the IP address the gNB has been assigned, and then
  after disconnecting from the LAN, connect to the GUI via this
  address. You will be on the same L2 subnet as the Aether server,
  which you should be able to ping using the gNB’s diagnostic tool.
  The default gateway DHCP returns does not know how to route data
  packets to the UPF. To fix this, modify the WAN settings to use a
  static IP, with the DHCP-provided IP used as the gNB's static
  address. Then set the default gateway to the IP address of your
  Aether server.

Run Diagnostics
~~~~~~~~~~~~~~~~~

Successfully connecting a UE to the Internet is not a straightforward
exercise. It involves configuring the UE, gNB, and SD-Core software in
a consistent way; establishing SCTP-based control plane (N2) and
GTP-based user plane (N3) connections between the base station and
Mobile Core; and traversing multiple IP subnets along the end-to-end
path.

The UE and gNB provide limited diagnostic tools. For example, it's
possible to run ``ping`` and ``traceroute`` from both. You can also
run the ``ksniff`` tool described in the Networking section, but the
most helpful packet traces you can capture are shown in the following
commands. You can run these on the Aether server, where we use our
example ``ens18`` interface for illustrative purposes:

.. code-block::

   $ sudo tcpdump -i any sctp -w sctp-test.pcap
   $ sudo tcpdump -i ens18 port 2152 -w gtp-outside.pcap
   $ sudo tcpdump -i access port 2152 -w gtp-inside.pcap
   $ sudo tcpdump -i core net 172.250.0.0/16 -w n6-inside.pcap
   $ sudo tcpdump -i ens18 net 172.250.0.0/16 -w n6-outside.pcap

The first trace, saved in file ``sctp.pcap``, captures SCTP packets
sent to establish the control path between the base station and the
Mobile Core (i.e., N2 messages). Toggling "Mobile Data" on the UE,
for example by turning Airplane Mode off and on, will generate the
relevant control plane traffic.

The second and third traces, saved in files ``gtp-outside.pcap`` and
``gtp-inside.pcap``, respectively, capture GTP packets (tunneled
through port ``2152`` ) on the RAN side of the UPF. Setting the
interface to ``ens18`` corresponds to "outside" the UPF and setting
the interface to ``access`` corresponds to "inside" the UPF.  Running
``ping`` from the UE will generate the relevant user plane (N3) traffic.

Similarly, the fourth and fifth traces, saved in files
``n6-inside.pcap`` and ``n6-outside.pcap``, respectively, capture IP
packets on the Internet side of the UPF (which is known as the **N6**
interface in 3GPP). In these two tests, ``net 172.250.0.0/16``
corresponds to the IP addresses assigned to UEs by the SMF. Running
``ping`` from the UE will generate the relevant user plane traffic.

If the ``gtp-outside.pcap`` has packets and the ``gtp-inside.pcap``
is empty (no packets captured), you may run the following commands
to make sure packets are forwarded from the ``ens18`` interface
to the ``access`` interface and vice versa:

.. code-block::

   $ sudo iptables -A FORWARD -i ens18 -o access -j ACCEPT
   $ sudo iptables -A FORWARD -i access -o ens18 -j ACCEPT

Support for eNBs
~~~~~~~~~~~~~~~~~~

Aether OnRamp is geared towards 5G, but it does support physical eNBs,
including 4G-based versions of both SD-Core and AMP. It does not
support an emulated 4G RAN. The 4G scenario uses all the same Ansible
machinery outlined in earlier sections, but uses a variant of
``vars/main.yml`` customized for running physical 4G radios:

.. code-block::

   $ cd vars
   $ cp main-eNB.yml main.yml

Assuming that starting point, the following outlines the key
differences from the 5G case:

1. There is a 4G-specific repo, which you can find in ``deps/4gc``.

2. The ``core`` section of ``vars/main.yml`` specifies a 4G-specific values file:

   ``values_file: "deps/4gc/roles/core/templates/radio-4g-values.yaml"``

3. The ``amp`` section of ``vars/main.yml`` specifies that 4G-specific
   models and dashboards get loaded into the ROC and Monitoring
   services, respectively:

   ``roc_models: "deps/amp/roles/roc-load/templates/roc-4g-models.json"``

   ``monitor_dashboard:  "deps/amp/roles/monitor-load/templates/4g-monitor"``

4. You need to edit two files with details for the 4G SIM cards you
   use. One is the 4G-specific values file used to configure SD-Core:

   ``deps/4gc/roles/core/templates/radio-4g-values.yaml``

   The other is the 4G-specific Models file used to bootstrap ROC:

   ``deps/amp/roles/roc-load/templates/radio-4g-models.json``

5. There are 4G-specific Make targets for SD-Core (e.g., ``make
   aether-4gc-install`` and ``make aether-4gc-uninstall``), but the
   Make targets for AMP (e.g., ``make aether-amp-install`` and ``make
   aether-amp-uninstall``) work unchanged in both 4G and 5G.

The Quick Start and Emulated RAN (gNBsim) deployments are for 5G only,
but revisiting the other sections—substituting the above for their 5G
counterparts—serves as a guide for deploying a 4G version of Aether.
Note that the network is configured in exactly the same way for both
4G and 5G. This is because SD-Core's implementation of the UPF is used
in both cases.