class QueueingSystem(Model):
"""QueueingSystem model represents a simple queue */*/1/N or */*/1,
where any distribution can be used for arrival and service times.
This model consists of four children:
- `queue`: a model representing the packets queue (`Queue`)
- `source`: a model representing the packets source (`Source`)
- `server`: a model representing the packets server (`Server`)
- `sink`: a model which collects served packets (`Sink`)
"""
def __init__(self, sim):
super().__init__(sim)
arrival = sim.params.arrival
service = sim.params.service
queue_capacity = sim.params.queue_capacity
self.children['queue'] = Queue(sim, queue_capacity)
self.children['source'] = Source(sim, arrival, index=0)
self.children['server'] = Server(sim, service)
self.children['sink'] = Sink(sim)
# Building connections:
self.source.connections['queue'] = self.queue
self.queue.connections['server'] = self.server
self.server.connections['queue'] = self.queue
self.server.connections['next'] = self.sink
# Statistics:
self.system_size_trace = Trace()
self.system_size_trace.record(self.sim.stime, 0)
self.system_wait_intervals = Statistic()
@property
def queue(self):
return self.children['queue']
@property
def source(self):
return self.children['source']
@property
def server(self):
return self.children['server']
@property
def sink(self):
return self.children['sink']
@property
def system_size(self):
return self.queue.size + (1 if self.server.busy else 0)
def update_system_size(self, index=0):
assert index == 0
self.system_size_trace.record(self.sim.stime, self.system_size)
def add_system_wait_interval(self, value, index=0):
assert index == 0
self.system_wait_intervals.append(value)
class Server(Model):
"""Server module represents a packet server with exponential service time.
Connections: queue, sink
Handlers:
- on_service_end(): called upon service timeout
Methods:
- start_service(): start new packet service; generate error if busy.
Statistics:
- delays: `Statistic`, stores a set of service intervals
- busy_trace: `Trace`, stores a vector of server busy status
Parent: `QueueingSystem`
"""
def __init__(self, sim, service_mean):
super().__init__(sim)
self.__service_mean = service_mean
self.__busy = False
# Statistics:
self.delays = Statistic()
self.busy_trace = Trace()
self.busy_trace.record(self.sim.stime, 0)
@property
def service_mean(self):
return self.__service_mean
@property
def busy(self):
return self.__busy
def on_service_end(self):
assert self.__busy
queue = self.connections['queue'].module
self.__busy = False
self.busy_trace.record(self.sim.stime, 0)
if queue.size > 0:
queue.pop()
self.start_service()
self.connections['sink'].module.receive_packet()
self.parent.update_system_size()
def start_service(self):
assert not self.__busy
delay = exponential(self.service_mean)
self.sim.schedule(delay, self.on_service_end)
self.delays.append(delay)
self.__busy = True
self.busy_trace.record(self.sim.stime, 1)
def test_statistic_append_adds_values():
st = Statistic()
st.append(1)
st.append(20)
assert st.as_tuple() == (1, 20)
def test_statistic_copy_data_content_instead_of_pointer():
data = [1, 2]
st = Statistic(data)
st.append(3)
assert st.as_tuple() == (1, 2, 3)
assert data == [1, 2]
class Server(Model):
"""Server module represents a packet server with exponential service time.
Connections: queue, sink
Handlers:
- on_service_end(): called upon service timeout
Methods:
- start_service(): start new packet service; generate error if busy.
Statistics:
- delays: `Statistic`, stores a set of service intervals
- busy_trace: `Trace`, stores a vector of server busy status
- num_served: `int`
Parent: `QueueingSystem`
"""
def __init__(self, sim, service_time, index=0):
super().__init__(sim)
self.service_time = service_time
self.packet = None
self.index = index
# Statistics:
self.service_intervals = Statistic()
self.busy_trace = Trace()
self.busy_trace.record(self.sim.stime, 0)
self.departure_intervals = Intervals()
self.departure_intervals.record(sim.stime)
self.num_served = 0
@property
def busy(self):
return self.packet is not None
@property
def ready(self):
return self.packet is None
def handle_service_end(self):
assert self.busy
stime = self.sim.stime
self.connections['next'].send(self.packet)
self.parent.add_system_wait_interval(stime - self.packet.arrived_at,
self.index)
self.packet = None
self.busy_trace.record(stime, 0)
self.departure_intervals.record(stime)
self.num_served += 1
# Requesting next packet from the queue:
queue = self.connections['queue'].module
if queue.size > 0:
self.serve(queue.pop())
self.parent.update_system_size(self.index)
def _start_service(self):
delay = self.service_time()
self.sim.schedule(delay, self.handle_service_end)
return delay
def serve(self, packet):
assert not self.busy
self.packet = packet
delay = self._start_service()
self.service_intervals.append(delay)
self.busy_trace.record(self.sim.stime, 1)
class Queue(Model):
"""Queue module represents the packets queue, stores only current size.
Connections: server
Methods and properties:
- push(): increase the queue size
- pop(): decrease the queue size
- size: get current queue size
Statistics:
- size_trace: Trace, holding the history of the queue size updates
- num_arrived: `int`
- num_dropped: `int`
- drop_ratio: `float`
"""
def __init__(self, sim, capacity, index=0):
super().__init__(sim)
self.__capacity = capacity
self.packets = deque()
self.index = index
# Statistics:
self.size_trace = Trace()
self.size_trace.record(self.sim.stime, 0)
self.num_dropped = 0
self.arrival_intervals = Intervals()
self.arrival_intervals.record(sim.stime)
self.num_arrived = 0
self.wait_intervals = Statistic()
@property
def capacity(self):
return self.__capacity
@property
def size(self):
return len(self.packets)
@property
def drop_ratio(self):
if self.num_arrived == 0:
return 0
return self.num_dropped / self.num_arrived
def handle_message(self, message, connection=None, sender=None):
self.push(message)
def push(self, packet):
self.arrival_intervals.record(self.sim.stime)
self.num_arrived += 1
server = self.connections['server'].module
packet.arrived_at = self.sim.stime
if self.size == 0 and not server.busy:
server.serve(packet)
self.wait_intervals.append(self.sim.stime - packet.arrived_at)
elif self.capacity is None or self.size < self.capacity:
self.packets.append(packet)
self.size_trace.record(self.sim.stime, self.size)
else:
self.num_dropped += 1
self.parent.update_system_size(self.index)
def pop(self):
packet = self.packets.popleft()
self.size_trace.record(self.sim.stime, self.size)
self.wait_intervals.append(self.sim.stime - packet.arrived_at)
return packet
def __str__(self):
return f'Queue({self.size})'
class WiredTransceiver(Model):
"""This module models a simple wired full-duplex transceiver.
`WiredTransceiver` simulates a simple wired network card. It sends packets
in `WireFrame`s instances with constant bitrate. Each frame can have
a preamble and some header. After transmission, `WiredTransceiver` waits
IFS before sending another frame.
`WiredTransceiver` receives data from the queue. Upon construction, it
schedules `_start()` call, which will request data from the queue. Note
that `'queue'` connection MUST be added right after creation to make this
work. Upon `_start()` call, `WiredTransceiver` will request packets with
`queue.get_next(self)` call.
`WiredTransceiver` requests other packets when TX operation finishes and
it waits IFS. To request additional packets, it calls `queue.get_next()`.
`WiredTransceiver` is expected to have the only one peer, which typically
is another `WiredTransceiver` module. They MUST be connected with `'peer'`
bi-directional connection. Reception is performed in two steps: when
the frame reaches the transceiver, it marks RX as busy, and schedules
frame reception end at `frame.duration`. Upon frame RX end, RX is marked
as ready.
If `WiredTransceiver` receives a packet from the `Queue` during another
TX operation running, it will throw a `RuntimeError` exception.
`WiredTransceiver` needs three connections:
- `'peer'`: a bi-directional connection to another transceiver (mandatory);
- `'queue'`: a bi-directional connection to the packets queue (mandatory);
- `'up'`: a bi-directional connection to the switch (optional).
If `'up'` connection is defined, the received packets are sent through it.
Otherwise, they are silently dropped. Typically, `'up'` connects a
`NetworkSwitch` module, or parent `NetworkInterface`.
"""
def __init__(self, sim, bitrate=inf, header_size=0, preamble=0, ifs=0):
super().__init__(sim)
self.bitrate = bitrate
self.header_size = header_size
self.preamble = preamble
self.ifs = ifs
# State variables:
self.__started = False
self.__tx_frame = None
self.__wait_ifs = False
self.__rx_frame = None
# Statistics:
self.__num_received_frames = 0
self.__num_received_bits = 0
self.__rx_busy_trace = Trace()
self.__rx_busy_trace.record(0, 0)
self.__num_transmitted_packets = 0
self.__num_transmitted_bits = 0
self.__tx_busy_trace = Trace()
self.__tx_busy_trace.record(0, 0)
self.__service_time = Statistic()
self.__service_started_at = None
# Initialization:
self.sim.schedule(self.sim.stime, self.start)
@property
def started(self):
return self.__started
@property
def tx_ready(self):
return not self.tx_busy
@property
def tx_busy(self):
return self.__tx_frame is not None or self.__wait_ifs
@property
def rx_ready(self):
return self.__rx_frame is None
@property
def rx_busy(self):
return not self.rx_ready
@property
def num_received_frames(self):
return self.__num_received_frames
@property
def num_received_bits(self):
return self.__num_received_bits
@property
def rx_busy_trace(self):
return self.__rx_busy_trace
@property
def num_transmitted_packets(self):
return self.__num_transmitted_packets
@property
def num_transmitted_bits(self):
return self.__num_transmitted_bits
@property
def tx_busy_trace(self):
return self.__tx_busy_trace
@property
def service_time(self):
return self.__service_time
@property
def tx_frame(self):
return self.__tx_frame
def start(self):
self.connections['queue'].module.get_next(self)
self.__started = True
def handle_message(self, message, connection=None, sender=None):
if connection.name == 'queue':
if self.tx_busy:
raise RuntimeError(
'new NetworkPacket while another TX running')
duration = ((self.header_size + message.size) / self.bitrate +
self.preamble)
frame = WireFrame(packet=message,
duration=duration,
header_size=self.header_size,
preamble=self.preamble)
self.connections['peer'].send(frame)
self.sim.schedule(duration, self.handle_tx_end)
self.__tx_frame = frame
self.__tx_busy_trace.record(self.sim.stime, 1)
self.__service_started_at = self.sim.stime
self.sim.logger.debug(f'start transmitting frame {frame}',
src=self)
elif connection.name == 'peer':
self.sim.schedule(message.duration,
self.handle_rx_end,
args=(message, ))
self.__rx_frame = message
self.__rx_busy_trace.record(self.sim.stime, 1)
self.sim.logger.debug(f'start receiving frame {message}', src=self)
def handle_tx_end(self):
self.sim.schedule(self.ifs, self.handle_ifs_end)
# Record statistics:
self.__num_transmitted_packets += 1
self.__num_transmitted_bits += self.__tx_frame.size
# Update state variables:
self.__wait_ifs = True
self.__tx_frame = None
self.sim.logger.debug(f'finish transmitting, waiting IFS', src=self)
def handle_ifs_end(self):
self.__wait_ifs = False
self.connections['queue'].module.get_next(self)
# Record statistics:
self.__tx_busy_trace.record(self.sim.stime, 0)
self.__service_time.append(self.sim.stime - self.__service_started_at)
self.__service_started_at = None
self.sim.logger.debug(f'IFS end, ready to transmit', src=self)
def handle_rx_end(self, frame):
if 'up' in self.connections:
self.connections['up'].send(frame.packet)
self.__rx_frame = None
self.__num_received_frames += 1
self.__num_received_bits += frame.size
self.__rx_busy_trace.record(self.sim.stime, 0)
self.sim.logger.debug(f'finish receiving frame', src=self)
def __str__(self):
prefix = f'{self.parent}.' if self.parent else ''
return f'{prefix}RxTx'
class Transmitter(Model):
"""Models transmitter module at MAC layer.
Connections:
- `'channel'`: mandatory, to `Channel` instance;
- `'radio'`: mandatory, to `Radio` module
- `'queue'`: optional, to `Queue` module
"""
class State(Enum):
IDLE = 0
BUSY = 1
BACKOFF = 2
TX = 3
WAIT_ACK = 4
def __init__(
self,
sim,
address=None,
phy_header_size=None,
mac_header_size=None,
ack_size=None,
bitrate=None,
preamble=None,
max_propagation=0,
):
super().__init__(sim)
# Properties:
self.__address = address
self.__phy_header_size = (phy_header_size if phy_header_size
is not None else sim.params.phy_header_size)
self.__mac_header_size = (mac_header_size if mac_header_size
is not None else sim.params.mac_header_size)
self.__bitrate = bitrate if bitrate is not None else sim.params.bitrate
self.__preamble = (preamble
if preamble is not None else sim.params.preamble)
self.__max_propagation = max_propagation
self.__ack_size = (ack_size
if ack_size is not None else sim.params.ack_size)
# State variables:
self.timeout = None
self.cw = 65536
self.backoff = -1
self.num_retries = None
self.pdu = None
self.__state = Transmitter.State.IDLE
self.__seqn = 0
# Statistics:
self.backoff_vector = Statistic()
self.__start_service_time = None
self.service_time = Statistic()
self.num_sent = 0
self.num_retries_vector = Statistic()
self.__busy_trace = Trace()
self.__busy_trace.record(sim.stime, 0)
# Initialize:
sim.schedule(0, self.start)
@property
def state(self):
return self.__state
@state.setter
def state(self, state):
if self.state != state:
self.sim.logger.debug(f'{self.state.name} -> {state.name}',
src=self)
self.__state = state
@property
def address(self):
return self.__address
@address.setter
def address(self, address):
self.__address = address
@property
def phy_header_size(self):
return self.__phy_header_size
@property
def mac_header_size(self):
return self.__mac_header_size
@property
def ack_size(self):
return self.__ack_size
@property
def bitrate(self):
return self.__bitrate
@property
def preamble(self):
return self.__preamble
@property
def max_propagation(self):
return self.__max_propagation
@property
def busy_trace(self):
return self.__busy_trace
@property
def channel(self):
return self.connections['channel'].module
@property
def radio(self):
return self.connections['radio'].module
@property
def queue(self):
return self.connections['queue'].module
def start(self):
self.queue.get_next(self)
def handle_message(self, packet, connection=None, sender=None):
if connection.name == 'queue':
assert self.state == Transmitter.State.IDLE
self.cw = self.sim.params.cwmin
self.backoff = randint(0, self.cw)
self.num_retries = 1
#
# Create the PDU:
#
self.pdu = DataPDU(packet,
seqn=self.__seqn,
header_size=self.phy_header_size +
self.mac_header_size,
sender_address=self.address,
receiver_address=packet.receiver_address)
self.__seqn += 1
self.__start_service_time = self.sim.stime
self.backoff_vector.append(self.backoff)
self.__busy_trace.record(self.sim.stime, 1)
self.sim.logger.debug(
f'backoff={self.backoff}; CW={self.cw},NR={self.num_retries}',
src=self)
if self.channel.is_busy:
self.state = Transmitter.State.BUSY
else:
self.state = Transmitter.State.BACKOFF
self.timeout = self.sim.schedule(self.sim.params.difs,
self.handle_backoff_timeout)
else:
raise RuntimeError(
f'unexpected handle_message({packet}, connection={connection}, '
f'sender={sender}) call')
def channel_ready(self):
if self.state == Transmitter.State.BUSY:
self.timeout = self.sim.schedule(self.sim.params.difs,
self.handle_backoff_timeout)
self.state = Transmitter.State.BACKOFF
def channel_busy(self):
if self.state == Transmitter.State.BACKOFF:
self.sim.cancel(self.timeout)
self.state = Transmitter.State.BUSY
def finish_transmit(self):
if self.state == Transmitter.State.TX:
self.sim.logger.debug('TX finished', src=self)
ack_duration = (
(self.ack_size + self.mac_header_size + self.phy_header_size) /
self.bitrate + self.preamble + 6 * self.max_propagation)
self.timeout = self.sim.schedule(
self.sim.params.sifs + ack_duration, self.handle_ack_timeout)
self.state = Transmitter.State.WAIT_ACK
def acknowledged(self):
if self.state == Transmitter.State.WAIT_ACK:
self.sim.logger.debug('received ACK', src=self)
self.sim.cancel(self.timeout)
self.pdu = None
self.state = Transmitter.State.IDLE
self.num_sent += 1
self.service_time.append(self.sim.stime -
self.__start_service_time)
self.__start_service_time = None
self.num_retries_vector.append(self.num_retries)
self.num_retries = None
self.__busy_trace.record(self.sim.stime, 0)
#
# IMPORTANT: Informing the queue that we can handle the next packet
#
self.queue.get_next(self)
def handle_ack_timeout(self):
assert self.state == Transmitter.State.WAIT_ACK
self.num_retries += 1
self.cw = min(2 * self.cw, self.sim.params.cwmax)
self.backoff = randint(0, self.cw)
self.backoff_vector.append(self.backoff)
self.sim.logger.debug(
f'backoff={self.backoff}; CW={self.cw}, NR={self.num_retries})',
src=self)
if self.channel.is_busy:
self.state = Transmitter.State.BUSY
else:
self.state = Transmitter.State.BACKOFF
self.timeout = self.sim.schedule(self.sim.params.difs,
self.handle_backoff_timeout)
def handle_backoff_timeout(self):
if self.backoff == 0:
self.state = Transmitter.State.TX
self.sim.logger.debug(f'transmitting {self.pdu}', src=self)
self.radio.transmit(self.pdu)
else:
assert self.backoff > 0
self.backoff -= 1
self.timeout = self.sim.schedule(self.sim.params.slot,
self.handle_backoff_timeout)
self.sim.logger.debug(f'backoff := {self.backoff}', src=self)
def __str__(self):
prefix = f'{self.parent}.' if self.parent else ''
return f'{prefix}transmitter'