Lab 2: 4G LTE

In this experiment, we deploy a simple 4G LTE network using Software Radio Systems (SRS) LTE Zero-MQ (ZMQ) simulator. In this lab, we do not have a T-Tracer to pause the RAN execution, hence to capture all the packets, you need to open the Wireshark immediately after the core network (EPC) is ready.

To prepare Wireshark environment, before the installation of the network, in a separate terminal, run the following commands. Like before the ports 5687 and 5847 are temporary ports used by the SRS LTE for dumping the MAC layer packets.

udp_ports="2123 or 2152 or 5687 or 5847"
sctp_ports="38412 or 38472 or 36421 or 36412"
filter="(sctp port $sctp_ports) or (udp port $udp_ports)"

simple-lte.yaml

apiVersion: athena.trirematics.io/v1
kind: Network
metadata:
    name: eurecom
    namespace: trirematics
spec:
    slices:
        -   plmn: "00103"
            dnn: "internet"
            network-mode: "IPv4"
            service-type: eMBB
            differentiator: 0x000000
            ipv4-range: "12.1.1.0/24"
            ipv6-range: "2001:db8:1::/64"
    access:
        -   name: srs-lte
            stack: 4g-sa
            model: srs/srs-enb
            profiles:
                - pcap
            identity:
                an-id: 50
            radio:
                device: rf-sim
            cells:
                -   band: b7
                    arfcn: 3350
                    bandwidth: 10MHz
                    subcarrier-spacing: 15kHz
            annotations:
                extras.trirematics.io/ue-sim: srs-ue
            core-networks:
                - core.eurecom
    core:
        -   name: core
            stack: 4g-sa
            model: srs/srs-epc
            identity:
                region: 0
                cn-group: 4
                cn-id: 5
    dns:
        ipv4:
            default: 8.8.8.8
            secondary: 8.8.4.4
---
apiVersion: athena.trirematics.io/v1
kind: Terminal
metadata:
    name: srs-ue
    namespace: trirematics
spec:
    vendor: srs
    stack: 4g-sa
    model: terminal/srs-sim
    preferred-access: srs-lte.eurecom
    target-cores:
        - core.eurecom
    identity:
        imsi: "001030000000001"
        pin: "1234"
        opc: "0xc42449363bbad02b66d16bc975d77cc1"
        key: "0xfec86ba6eb707ed08905757b1bb44b8f"
        sqn: "0xff9bb4000001"
    slice:
        dnn: "internet"
        network-mode: "IPv4"
        service-type: eMBB
        differentiator: 0x000000
    radio:
        bands:
            - b7
    readiness-check:
        method: ping
        ip: 12.1.1.1
        interface-name: srs-ue

Deployment and PCAP

Use the command cli install network simple-lte.yaml to deploy the network. It should finish without errors and printout the two Kubernetes resource names that were created. Check for the status of the deployment using the command cli observe.

Right after the EPC is ready, open the Wireshark and start capturing the packets. To do so, run the following command:

cli extract pcap srs-enb.srs-lte.eurecom -- "$filter" | wireshark -k -i -

Then wait until all the Elements including the UE are in the STATUS set to 1/1 Y state.

💬 Questions

1. Explain the role of each of the Elements in the deployment.
2. Record the output of the observe by taking a screenshot and add it to your report.

UE Traffic

To verify the E2E connection, let us check the EPC and eNB logs. To do so, run the following command:

cli extract logs $element

You could use the Tab key to complete the name of the element.

💬 Questions

1. Explain what is each of the ports used for in 4G/5G interfaces and show the protocol stack.
2. Investigate if there is any user traffic in the PCAP already and if any the type of the traffic (after the UE readiness).
3. Generate some TCP DL traffic and measure the throughput via the --plot option.
4. Explain the differences between the cell configuration of this lab and the previous lab.

Uninstall

To uninstall the network, use the following command:

$ cli remove network simple-lte.yaml

Checking via the cli observe command, you should see that all the elements are removed.

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💬 Lab Questions 💬

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For the questions below, when applicable, verify the results both from the PCAP. If one piece of information is present in multiple messages, please specify all of them and explain the differences.

1. What are the IP addresses of eNB and MME? What is the port number of S1-MME?
2. What PLMN does the cell broadcast?
3. How many UEs are connected to the network?
4. What are the RNTIs of the connected UEs? What are their IMSIs and PLMNs? How do they signal their selected PLMN Identity?
5. Which logical channels are used during the RACH and RRC connection setup?
6. Map the RRC connection messages to the logical channels and RLC mode.
7. At what message number is the UE connected to the eNB and can start transmitting data?
8. At what message number does the UE have a data connection to the core network and internet?
9. Draw the message sequence chart and show the messages and their associated network entity (i.e. UE, eNB, MME)?