StormSim

Notice - StormSim source code may be temporarily hidden until 10/2026 while the project completes full support for the planned specifications and features listed in Future Work. If you want to use StormSim during this period, use the published Docker image and follow Simple way to run.

A scalable UE and gNodeB emulator for testing, validating, and benchmarking 5G Core networks. StormSim emulates thousands of UEs and gNodeBs that establish real NAS/NGAP signalling toward an actual 5G Core (AMF/SMF/UPF, e.g. free5GC or Open5GS). It is designed for stress-testing, regression validation, and performance benchmarking of the control plane.

Note - StormSim emulates the control plane (UE ↔ gNB ↔ AMF) and sets up N3 data-plane tunnels via the gtp5g kernel module of Free5gc. It is not a user-plane traffic generator.

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📚 Documentation

Document	Description
docs/how-to-config.md	How to configure StormSim: every config.yml block, field reference, scenarios, recipes, and gotchas
docs/how-to-use-oam-client.md	How to use the OAM client: command reference with sample output and metrics

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Features

Scale

• Each UE and gNB runs on a shared worker pool and tested up to 10,000 UEs + gNodeBs in a single run against a real 5G Core.

PCAP capture

• Capture signalling to a PCAP file with --pcap. StormSim attaches a live capture to the host interface that carries the gNodeB control plane (N2, which transports N1 NAS), so you get the full NAS/NGAP exchange in Wireshark.

NAS procedures (UE side, 5GMM / 5GSM)

• Registration (Initial / Periodic / Emergency)
• Deregistration (UE-initiated and network-initiated; switch-off & re-registration)
• PDU Session Establishment / Release (and modification)
• Service Request
• Identity / Authentication / Security Mode Control
• Configuration Update
• Paging
• Idle-mode ↔ Connected-mode transitions
• Handover: Xn handover (Path Switch Request) and N2 handover

NGAP procedures (gNB ↔ AMF)

• NG Setup
• Initial UE Message
• Uplink NAS Transport / Downlink NAS Transport
• Initial Context Setup (Request/Response)
• PDU Session Resource Setup / Release
• UE Context Release (Command/Complete)
• Paging
• Path Switch Request (Xn HO) and Handover Request/Command/Notify (N2 HO)
• AMF Configuration Update

NAS protocol timers (3GPP TS 24.501)

Each timer can be individually enabled/disabled in config defaultUe.timers: T3510, T3511, T3502, T3512, T3516, T3519, T3520, T3580, T3582

SUCI / Subscriber privacy

Status: Currently StormSim uses the Null-Scheme (unconcealed SUPI/IMSI). Profile A (X25519) and Profile B (P-256) ECIES concealing/deconcealing are not yet implemented - see Future Work.

Radio-link impairment (RLink)

Inject realistic radio-link conditions on the UE ↔ gNB path:

• Delay (rlink.delay_ms): random 0–N ms added per NAS message.
• Loss (rlink.loss_ratio): probability of dropping a NAS message (0.0–1.0).

Client / OAM & metrics

A remote OAM server (HTTP) plus an interactive client let you inspect and trigger events at runtime while a scenario is running, and collect per-transition delay statistics (mean, std-dev, P1–P99 percentiles), UE state histograms, and handover-delay metrics - see docs/how-to-use-oam-client.md.

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Future Work

• SUCI concealing/deconcealing - implement Profile A (X25519) and Profile B (P-256) ECIES (currently Null-Scheme only).
• FUZZ mode vs Replay mode:
  • FUZZ: randomized fault injection at the UE state/event level and at the NAS IE level (mutate information elements) to probe Core robustness.
  • Replay: record a signalling trace and deterministically replay it.
• Conditional Handover (CHO) and timer handling during handover (e.g. preserving/restarting 5GMM timers across the HO).

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Requirements

Component	Requirement
OS	Ubuntu 20.04 – 22.04
Linux kernel	5.4.* ≤ kernel ≤ 6.1.* (required by gtp5g; StormSim borrows it from free5GC)
Go	1.25+
SCTP	sudo apt install make lksctp-tools
Build tools	make, gcc (kernel headers for gtp5g)

The kernel upper bound (6.1.*) is a hard constraint of the gtp5g kernel module. Newer kernels (6.2+) are not supported until gtp5g catches up.

Make sure the gtp5g kernel module is built and loaded before running scenarios that establish PDU sessions.

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Simple way to run

Pull the published image from Docker Hub:

docker pull lvdund/stormsim:latest

Before running, make sure:

• the host is Linux
• the gtp5g kernel module is already built and loaded on the host

Run the emulator:

docker run --rm -it \
  --privileged \
  --network host \
  -v "$(pwd)/config:/app/config:ro" \
  lvdund/stormsim:latest

This starts the emulator with /app/config/config.yml inside the container, so your host directory should contain config/config.yml.

Run the client in interactive mode:

docker run --rm -it \
  --network host \
  --entrypoint client \
  lvdund/stormsim:latest

Run the client with a single command:

docker run --rm -it \
  --network host \
  --entrypoint client \
  lvdund/stormsim:latest list-ue

More client commands and examples are documented in docs/how-to-use-oam-client.md.

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Build & Compile

StormSim produces two binaries via make:

# Build both
make # = make build = make emulator client

# Or build individually
make emulator # → bin/emulator
make client # → bin/client

make clean # remove bin/

Binary	Purpose
bin/emulator	The simulator itself: loads a config, spawns UEs/gNBs, runs scenarios, and serves the OAM API.
bin/client	Command-line & interactive client that talks to the running emulator's OAM server (localhost:4000 by default).

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Running the Emulator

# With a config file
sudo ./bin/emulator -c config/config.yml

# With config + PCAP capture of the N2/N1 signalling
sudo ./bin/emulator -c config/config.yml --pcap capture.pcap

# Built-in configuration help
./bin/emulator --config-help

sudo is required because StormSim binds SCTP/SCTP sockets, attaches a live PCAP handle to a host interface, and manages gtp5g N3 tunnels.

The emulator will:

1. Load & validate the config.
2. Connect the gNB(s) to the AMF (NG Setup).
3. Spawn the configured UE groups and enqueue their events.
4. Serve the OAM API on remote.ip:remote.port (default 0.0.0.0:4000).

📖 Configuration is covered in docs/how-to-config.md; using the live client is covered in docs/how-to-use-oam-client.md.

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Contributor

• lvdund
• Phùng Kiều Hà
• Thái Quang Tùng

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Citation

@software{stormsim,
  author       = {VD},
  title        = {{StormSim}: A Scalable {UE} and {gNodeB} Emulator for Testing, Validating, and Benchmarking {5G Core} Networks},
  year         = {2025},
  publisher    = {GitHub},
  howpublished = {\url{https://github.com/lvdund/StormSIM}},
  note         = {Accessed: 2026-07-01}
}

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License

Licensed under the Apache License, Version 2.0. See LICENSE.

StormSIM uses gtp5g of free5gc for enabling gtp tunnel and learns design from UERANSIM vs PacketRusher.