DSL Reference

Topology builders

adapter = net.adapter("name", ip="10.0.0.1")          # NIC / host / server
switch  = net.switch("name",  ports=16, mode="store-and-forward")
hub     = net.hub("name",     ports=8)
broker  = net.mqtt_broker("name", ip="10.0.2.1")       # MQTT message broker
slave   = net.modbus_slave("name", ip="10.0.0.10", unit_id=1)  # Modbus TCP slave
net.link(a, b, speed=1_000, length=10)                 # Mb/s and metres

Multiple switches can be chained to model hierarchical topologies:

core_sw = net.switch("core-sw", ports=16, mode="store-and-forward")
edge_sw = net.switch("edge-sw", ports=8,  mode="store-and-forward")
net.link(edge_sw, core_sw, speed=1_000, length=5)      # inter-switch uplink

Traffic

# Basic Ethernet send
src.sends(to=dst, rate=8_000, size=1_518, pattern="constant")

# Delayed start (useful for staggered scenarios)
src.sends(to=dst, rate=8_000, size=1_518, pattern="constant", delay_ms=5_000)

# MQTT publish (sensor-style, constant-rate)
sensor.publishes(to=broker, topic="plant/temp", rate=1.0, payload=20, qos=1)
sensor.publishes(to=broker, topic="plant/temp", rate=1.0, payload=20, qos=0, delay_ms=2_000)

# Broker topic routing — must be called before simulate()
broker.routes("plant/temp", to=[server])

# Modbus TCP poll (master → slave, Read Holding Registers)
plc.polls(slave, register=40001, count=10, rate=1.0)
plc.polls(slave, register=30001, count=5, rate=2.0, delay_ms=500)

sends() parameters

Parameter	Type	Description
to	Adapter	Destination adapter
rate	float	Frames per second
size	int | "imix"	Frame size in bytes, or Internet Mix distribution
pattern	str	"constant", "poisson", or "bursty"
delay_ms	float	Simulation time before this flow starts (default 0)

publishes() parameters

Parameter	Type	Description
to	MQTTBroker	Target broker
topic	str	MQTT topic string
rate	float	Messages per second (default 1.0)
payload	int	Payload bytes (default 20)
qos	int	0 = fire-and-forget, 1 = PUBACK acknowledgement
delay_ms	float	Simulation time before publishing starts (default 0)

polls() parameters

Parameter	Type	Description
slave	ModbusSlave	Target slave to poll
register	int	Starting holding-register address
count	int	Number of registers to read
rate	float	Polls per second (default 1.0)
delay_ms	float	Simulation time before polling starts (default 0)

Traffic patterns

Pattern	Description
"constant"	Fixed inter-frame gap — models a saturated link
"poisson"	Exponentially distributed gaps — models random/bursty traffic
"bursty"	Pareto-distributed burst lengths — models ON/OFF sources

Frame sizes

Value	Description
integer	Fixed size in bytes (e.g. 512, 1_518)
"imix"	40 % × 64 B, 57 % × 594 B, 3 % × 1 518 B

Observations

net.observe(metric, on=node, every=interval_ms)

Metric	Unit	Observed on
throughput	Mb/s	Adapter
latency	µs	Adapter
frame_loss	%	Adapter
bytes_sent	MB	Adapter (sender)
bytes_received	MB	Adapter (receiver)
queue_depth	frames	Switch
utilization	%	Any node
collision_rate	/s	Hub
broker_queue	msgs	MQTTBroker
modbus_latency	µs	Adapter (master)

Simulation

result = net.simulate(duration=30_000)              # headless — silent, fastest
result = net.simulate(duration=30_000, text=True)   # rich text dashboard in terminal
result = net.simulate(duration=30_000, live=True)   # full Dear PyGui desktop window

result.report()   # print summary table (avg / min / max per metric)
result.plot()     # open static dashboard for a completed result

# Export metric time-series (format inferred from extension)
result.export("results.csv")    # long CSV: time_ms, metric, value
result.export("results.json")   # JSON dict of lists-of-pairs
result.export("out.csv", format="csv")   # explicit format override

Text mode (text=True) displays a live updating table in the terminal — no display server or GUI toolkit required. Ideal for headless servers, SSH sessions, and CI environments.