Emulated RAN

gNBsim emulates a 5G RAN, generating (mostly) Control Plane traffic that can be directed at SD-Core. This section describes how to configure gNBsim to customize and scale the workload it generates. We assume gNBsim runs in one or more servers, independent of the server(s) that host SD-Core. These servers are specified in the hosts.ini file, as described in the Scale Cluster section. This blueprint assumes you start with a variant of vars/main.yml customized for running gNBsim. This is easy to do:

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

Configure gNBsim

Two sets of parameters control gNBsim. The first set, found in the gnbsim section of vars/main.yml, controls how gNBsim is deployed: (1) the number of servers it runs on; (2) the number of Docker containers running within each server; (3) what configuration to run in each of those containers; and (4) how those containers connect to SD-Core. For example, consider the following variable definitions:

gnbsim:
    docker:
        container:
            image: omecproject/5gc-gnbsim:main-PR_88-cc0d21b
            prefix: gnbsim
            count: 2
        network:
           macvlan:
                name: gnbnet

    router:
       data_iface: ens18
       macvlan:
            iface: gnbaccess
            subnet_prefix: "172.20"

    servers:
        0:
           - "config/gnbsim-s1-p1.yaml"
           - "config/gnbsim-s1-p2.yaml"
        1:
           - "config/gnbsim-s2-p1.yaml"
           - "config/gnbsim-s2-p2.yaml"

The container.count variable in the docker block specifies how many containers run in each server (2 in this example). The router block then gives the network specification needed for these containers to connect to the SD-Core; all of these variables are described in the Verify Network section. Finally, the servers block names the configuration files that parameterize each container. In this example, there are two servers with two containers running in each, with config/gnbsim-s2-p1.yaml parameterizing the first container on the second server.

These config files then specify the second set of gNBsim parameters. A detailed description of these parameters is outside the scope of this guide (see https://github.com/omec-project/gnbsim for details), but at a high-level, gNBsim defines a set of profiles, each of which exercises a common usage scenario that the Core has to deal with. Each of these sequences is represented by a profileType in the config file. gNBsim supports seven profiles, which we list here:

- profileType: register              # UE Registration
- profileType: pdusessest            # UE Initiated Session
- profileType: anrelease             # Access Network (AN) Release
- profileType: uetriggservicereq     # UE Initiated Service Request
- profileType: deregister            # UE Initiated De-registration
- profileType: nwtriggeruedereg      # Network Initiated De-registration
- profileType: uereqpdusessrelease   # UE Initiated Session Release

The second profile (pdusettest) is selected by default. It causes the specified number of UEs to register with the Core, initiate a user plane session, and then send a minimal data packet over that session. Note that the rest of the per-profile parameters are highly redundant. For example, they specify the IMSI- and PLMD-related information UEs need to connect to the Core.

Finally, it is necessary to edit the core section of vars/main.yml to indicate the address at which gNBsim can find the AMF. For our running example, this would look like the following:

core:
    amf: "10.76.28.113"

Install/Uninstall gNBsim

Once you have edited the parameters (and assuming you already have SD-Core running), you are ready to install gNBsim. This includes starting up all the containers and configuring the network so they can reach the Core. This is done from the main OnRamp server you’ve been using, where you type:

$ make gnbsim-docker-install
$ make aether-gnbsim-install

Note that the first step may not be necessary, depending on whether Docker is already installed on the server(s) you’ve designated to host gNBsim.

When you are finished, the following uninstalls everything:

$ make aether-gnbsim-uninstall

Run gNBsim

Once gNBsim is installed and the Docker containers instantiated, you can run the simulation by typing

$ make aether-gnbsim-run

This can be done multiple times without reinstalling. For each run, you can use Docker to view the results, which have been saved in each of the containers. To do so, ssh into one of the servers designated to to run gNBsim, and then type

$ docker exec -it gnbsim-1 cat summary.log

Note that container name gnbsim-1 is constructed from the prefix variable defined in the docker section of vars/main.yml, with -1 indicating the first container.

In addition to scaling up the workload you put on the Core, you can also experiment with the emulation settings defined in any or all of the config files in deps/gnbsim/config/. Focusing on profile2 in particular (because it sends data packets after registering each UE), variable defaultAs: "192.168.250.1" specifies the target of ICMP Echo Request packets. Changing the value to the IP address of a real-world server (e.g., 8.8.8.8) causes the emulated UE to actually ping that server. Success is a good indication that your Aether cluster is properly configured to support end-to-end connectivity.

Yet another option is to configure a single instance of gNBsim to direct multiple workloads at SD-Core. For example, editing vars/main.yml to use config/gnbsim-all.yaml in place of config/gnbsim-default.yaml causes gNBsim to activate all the profiles.