5G Core Operators

5G-Core is used to deploy a standalone working 5G Core setup. It is implemented as microk8s applications using Juju Charms and Microk8s. It consists of the following 12 components of 5G Core as charms,

• mongodb: Database of 5G Core
• nrf: Network Repository Function maintains an updated repository of all the 5g core components along with the services they provide
• amf: Access and Mobility Management Function is used in control plane interaction with RAN
• ausf: Authentication Server Function manages 5G UE authentication
• nssf: Network Selection Function used to select the network slice instance of 5g components
• pcf: Policy Control Function provides policy based rules to control plane functions.
• udm: Unified Data Management manages user information in a centralized manner. Manages data for user registration, authorization and networks.
• udr: Unified Data Repository serves as a unified database for storing information about application, subscription and authentication.
• webui: User Interface for adding/removing IMSI information
• upf1: User Plane Function is used in data plane interaction with RAN
• smf: Session Management Function is used for interacting with data plane and creating and managing PDU sessions
• natapp: NAT application to enable data network accessibility

Usage

Prepare environment

A. Prerequisites

a. Linux Kernel Version

The Linux kernel version of 5.0.0-23-generic is mandatory to use the UPF component. To check the version of the existing Linux kernel,

uname -r

If the existing kernel version is not 5.0.0-23-generic, then install it using,

sudo apt-get install linux-image-5.0.0-23-generic linux-headers-5.0.0-23-generic

For all popups just press enter with the option two selected. Then,

sudo reboot

b. Install Gtp5g module

• Gcc Installation:

  sudo apt update
  sudo apt install gcc
  sudo apt update
  sudo apt install make

• Clone Gtp5g Module:

  git clone https://github.com/PrinzOwO/gtp5g.git --branch v0.1.0

• Build:

  cd gtp5g
  make
  sudo make install

• Verification:

  lsmod | grep gtp5g

B. Install Microk8s

a. Install Microk8s using the following commands,

sudo snap install microk8s --classic --channel 1.19/stable
sudo usermod -a -G microk8s `whoami`
newgrp microk8s
microk8s.status --wait-ready

The ouput "microk8s is running" signifies that Microk8s is successfully installed.

b. Enable the following required addons for Microk8s to deploy 5G Core

microk8s.enable storage dns
microk8s.enable multus
microk8s.enable rbac
microk8s.enable metallb

NOTE: 5G Core requires 3 loadbalancer IP addresses mandatorily. So allocate 3 IP addresses while enabling metallb.

c. A configuration change is needed in the cluster for enabling SCTP traffic.

vi /var/snap/microk8s/current/args/kube-apiserver
//add the below line into the file
--feature-gates="SCTPSupport=true"
//Followed by stop and start of the cluster
microk8s.stop
microk8s.start

C. Install Juju

a. Install Juju with the following commands,

sudo snap install juju --classic --channel 2.8/stable
juju bootstrap microk8s

Deploy

To deploy 5G Core from Charmstore, use the following steps

a. Deploy core applications

juju deploy cs:~tataelxsi-charmers/core-5g

b. Configuring interface

For the deployment to get completed successfully, update master_interface field to your server's main interface name with the following command,

juju config natapp master_interface="<interface_name>"

where interface_name stands for server's main interface name where core is deployed

Deploy from local repository

To deploy 5G Core from local repository, follow the steps below,

a. Clone the 5G-Core repository

git clone https://github.com/charmed-osm/5g-core
cd 5g-core/

b. Enable Microk8s registry for storing images

microk8s.enable registry

c. Build 5G Core images

./build_docker_images.sh

d. Push built images to registry

docker push localhost:32000/free5gc-mongo:1.0
docker push localhost:32000/free5gc-nrf:1.0
docker push localhost:32000/free5gc-amf:1.0
docker push localhost:32000/free5gc-ausf:1.0
docker push localhost:32000/free5gc-nssf:1.0
docker push localhost:32000/free5gc-udm:1.0
docker push localhost:32000/free5gc-udr:1.0
docker push localhost:32000/free5gc-pcf:1.0
docker push localhost:32000/free5gc-upf-1:1.0
docker push localhost:32000/free5gc-webui:1.0
docker push localhost:32000/free5gc-smf:1.0
docker push localhost:32000/free5gc-natapp:1.0

e. Execute the following script to build all the 5G Core charms using Charmcraft,

./build_charms.sh

f. Create a model in Juju and deploy 5G Core,

juju add-model 5g-core
juju deploy ./bundle_local.yaml

g. Configuring interface

For the deployment to get completed successfully, update master_interface field to your server's main interface name with the following command,

juju config natapp master_interface="<interface_name>"

where interface_name stands for server's main interface name where core is deployed

Integration

5G Core exposes its following services as loadbalancer services in order to facilitate control plane and data plane interactions with RAN,

• AMF SCTP Service - For Control Plane User Registration and Attach Scenario.
• MongoDB Service - For mongodb operations
• UPF GTP Service - To enable data plane and data network accessbility to UE

In order to achieve this, 5G Core needs 3 Loadbalancer services to be exposed and published. This is done using the below command,

microk8s.enable metallb

NOTE: 5G Core requires 3 loadbalancer IP addresses mandatorily. Ignore this step if already done in pre-requisites.

Juju Actions

a. Action "config-interface" in UPF1 to configure the MTU size of the upfgtp0 interface of UPF application,

juju run-action upf1/<unit_id> config-interface

where unit_id is the Unit number of the deployed application.

b. Action "add-user" in mongodb to add subscriber information to core,

juju run-action mongodb/<unit_id> add-user ue-id=<IMSI_Number>

where unit_id is the Unit number of the deployed application, IMSI_Number is the IMSI number of the subscriber to be added in 5G-Core. imsi-2089300007487 is an example of IMSI number format.

After executing each action, an ID will be generated like below, Action queued with id: "ID" This ID can be used to check the action status using the following command,

juju show-action-output <ID>

Check for the status of the action in the output which should be "completed".

Actions Verification

a. "config-interface" in upf1 has to be verified with the following command,

ifconfig

Check for the MTU size of upfgtp0 interface which would have been set to 1440.

b. To verify “add-user”, login to mongodb application pod and verify the successful addition of imsi number,

mongo mongodb://db/free5G use free5gc
show collections
db.policyData.ues.amData.find()

where the imsi number added can be found under under key ueid.

5G Scenarios

5G User Registration

After 5G-Core and 5G-RAN(https://github.com/charmed-osm/5g-ran) are deployed and actions are completed, the user registration can be triggered through the following rest API call with POST method,

http://ran-loadbalancerip:8081/attachtrigger/1

Sample response for successful attach, Response Message: "Triggered Attach for the requested UE!" Response Code: 200 OK

Internet Traffic Flow

Once registration is successful, 5G-RAN's UE application would be enabled to access the data network. Test the following in UE application,

a. ICMP TRAFFIC

ping 8.8.8.8

b. TCP TRAFFIC

wget google.com

c. UDP TRAFFIC

nc -u <netcat server-ip> port

where netcat server-ip is the IP address of the server where netcat server is running. Note: for UDP traffic netcat server should be running in another server. To do that use the following commands in another server.

apt-get install netcat
nc -u -l -p <any unused port>

Voice Traffic Flow

Voice traffic flow can be tested once 5G-Core, 5G-RAN(https://github.com/charmed-osm/5g-ran) and 5G-IMS(https://github.com/charmed-osm/5g-ims) are deployed and actions are completed. To test voice traffic flows, a SIP client called PJSIP is already installed in the UE application. Follow the below steps in UE application,

a. Traverse to /pjproject directory in the UE pod.

b. alice.cfg is configured for an user named alice which is already available in IMS by default.

Note: The username, password and id can be changed to any user added from day-2 action of IMS as well.

c. Add the following content to /etc/hosts file,

<PCSCF_LB_IP> mnc001.mcc001.3gppnetwork.org <PCSCF-LB_IP> pcscf.mnc001.mcc001.3gppnetwork.org

Where <PCSCF-LB_IP> is the loadbalancer IP of PCSCF application and mnc001.mcc001.3gppnetwork.org is the domain added in coredns of IMS cluster.

d. Execute the following command to register the user alice with IMS,

pjsua --config-file alice.cfg --log-level=3

Note: Peform the above steps in another server to register another user say bob with IMS so that SIP calls can be tested between the two users.

e. After registration of both users, press ‘m’ from UE application's alice and then press enter to initiate a SIP call.

f. Give bob’s id and then press enter. The message “Calling” can be observed in alice’s UE pod.

g. Then in bob’s server, the following message can be seen,

Press ‘a’ to answer or ‘h’ to hangup

h. Press a and then enter. Then the following message will be displayed,

Answer with code:

i. Type 200 and enter.

j. After this “Confirmed” message can be seen in both alice and bob indicating that the call between alice and bob is successful and that RTP packets are being sent between alice and bob. The same can be verified by capturing SIP packets using ngrep, tcpdump or wireshark.

k. Then to end/hangup the call, press h and then enter from alice. Verify the “Disconnected” message in both alice and bob.

Testing

Run Integration and Unit tests to test and verify the 5G Core Charms.

Integration tests

Functional tests for 5G Core were created using zaza.

Install tox

apt-get install tox

Run Integration Test

To run zaza integration test,

tox -e func_test

This command will create a model, deploy the charms, run tests and destroy the model.

Unit tests

Unit tests has to be executed in all the 5G Core components/charms. The following commands show how to perform unit test in AMF,

cd charms/amf-operator
./run_tests

Similarly, unit tests can be run for all the other components/charms.

Get in touch

Found a bug?: https://github.com/charmed-osm/5g-core/issues Email: [email protected]