class TCP(Connection):
''' A TCP connection between two hosts.'''
def __init__(self,
transport,
source_address,
source_port,
destination_address,
destination_port,
app=None,
window=1000):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# Round trip time in seconds
self.estimated_rtt = None
# Deviation of sample rtt from estimated rtt
self.deviation_rtt = None
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
# a list of all the queuing delays from the sender to receiver
self.queueing_delay_list = []
def trace(self, message):
''' Print debugging messages. '''
Sim.trace("TCP", message)
def receive_packet(self, packet):
''' Receive a packet from the network layer. '''
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self, data):
''' Send data on the connection. Called by the application. This
code uses the SendBuffer to send incrementally '''
self.send_buffer.put(data)
self.queue_packets()
def queue_packets(self):
''' Send the next set of packets if there's any to send. Limit based
on window size and the number of outstanding packets '''
while True:
if self.send_buffer.available() <= 0:
break
if self.send_buffer.outstanding() + self.mss > self.window:
break
packet_data = self.send_buffer.get(self.mss)
self.send_packet(packet_data[0], packet_data[1])
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,
ack_number=self.ack,
sent_time=Sim.scheduler.current_time())
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
def handle_ack(self, packet):
''' Handle an incoming ACK. '''
# Calculate Sample RTT
sample_rtt = Sim.scheduler.current_time() - packet.sent_time
self.trace("sample round trip time %f" % sample_rtt)
# Calculate the new estimated RTT
alpha = 0.125
if not self.estimated_rtt:
self.estimated_rtt = sample_rtt
else:
self.estimated_rtt = (
1 - alpha) * self.estimated_rtt + alpha * sample_rtt
# Calculate the deviation of the sample RTT
beta = 0.25
if not self.deviation_rtt:
self.deviation_rtt = self.estimated_rtt / 2
else:
self.deviation_rtt = (1 - beta) * self.deviation_rtt + beta * abs(
sample_rtt - self.estimated_rtt)
# Calculate the Retransmission Timeout (RTO)
self.timeout = self.estimated_rtt + 4 * self.deviation_rtt
self.trace("changed the timeout to %f" % self.timeout)
self.sequence = packet.ack_number
self.send_buffer.slide(packet.ack_number)
self.cancel_timer()
if self.send_buffer.outstanding() or self.send_buffer.available():
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
self.queue_packets()
def retransmit(self, event):
''' Retransmit data. '''
self.trace("%s (%d) retransmission timer fired" %
(self.node.hostname, self.source_address))
packet_data = self.send_buffer.resend(self.mss)
self.send_packet(packet_data[0], packet_data[1])
self.timeout = self.timeout * 2
self.trace("doubled the timeout to %f" % self.timeout)
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
def cancel_timer(self):
''' Cancel the timer. '''
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self, packet):
''' Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK.'''
self.queueing_delay_list.append(packet.queueing_delay)
self.trace("%s (%d) received TCP segment from %d for %d" %
(self.node.hostname, packet.destination_address,
packet.source_address, packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
data = self.receive_buffer.get()
self.ack = len(data[0]) + data[1]
self.app.receive_data(data[0])
self.send_ack(packet.sent_time)
def send_ack(self, packet_sent_time=0):
''' Send an ack. '''
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,
ack_number=self.ack,
sent_time=packet_sent_time)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
''' A TCP connection between two hosts.'''
def __init__(self,
transport,
source_address,
source_port,
destination_address,
destination_port,
app=None,
window=1000,
threshold=100000,
fast_recovery=False,
aiad=False,
aimdc=0.5):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time (cwnd)
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# Round trip time in seconds
self.estimated_rtt = None
# Deviation of sample rtt from estimated rtt
self.deviation_rtt = None
# State determines slow start vs. additive increase
# 0 = slow start
# 1 = additive increase
self.state = 0
# Threshold for slow start
self.threshold = threshold
self.trace("Threshold starting at %d" % self.threshold)
# Same ack count (used for calculating three duplicate acks)
self.same_ack_count = 0
# Most recent ack (used for calculating three duplicate acks)
self.last_ack = None
# Make sure settings start with slow start
self.window = self.mss
# Used when dropping certain packets
self.dropped_count = 0
# Fast Recovery (Reno)
self.fast_recovery = fast_recovery
# AIAD
self.aiad = aiad
# AIMD Constant
self.aimdc = aimdc
### Used to make TCP Sequence Graphs
self.x = []
self.y = []
self.dropX = []
self.dropY = []
self.ackX = []
self.ackY = []
### Used to make window size graphs
self.window_x = []
self.window_y = []
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
# a list of all the queuing delays from the sender to receiver
self.queueing_delay_list = []
# keep track of when packets were received
self.packets_received = {}
def trace(self, message):
''' Print debugging messages. '''
Sim.trace("TCP", message)
def receive_packet(self, packet):
''' Receive a packet from the network layer. '''
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
# Record the current time and congestion window size
def recordWindow(self):
self.window_x.append(Sim.scheduler.current_time())
self.window_y.append(self.window)
# Record packets sent for plotting purposes
def recordPacketSent(self, time, sequence):
self.x.append(time)
self.y.append((sequence / 1000) % 50)
# Record packets dropped for plotting purposes
def recordPacketDropped(self, time, sequence):
self.dropX.append(time)
self.dropY.append((sequence / 1000) % 50)
# Record acks received for plotting purposes
def recordAckReceived(self, time, sequence):
self.ackX.append(time)
self.ackY.append((sequence / 1000) % 50)
def send(self, data):
''' Send data on the connection. Called by the application. This
code uses the SendBuffer to send incrementally '''
self.send_buffer.put(data)
self.queue_packets()
def queue_packets(self):
''' Send the next set of packets if there's any to send. Limit based
on window size and the number of outstanding packets '''
while True:
if self.send_buffer.available() <= 0:
break
open_window_space = self.window - self.send_buffer.outstanding()
if open_window_space <= 0:
break
# Send nice MSS sized packets
if open_window_space < self.mss:
break
packet_size = min(open_window_space, self.mss)
packet_data = self.send_buffer.get(packet_size)
self.send_packet(packet_data[0], packet_data[1])
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,
ack_number=self.ack,
sent_time=Sim.scheduler.current_time())
# Forced Loss, loss, AIMD dropped packets
drop_list = []
#drop_list = [32000] # For a single loss
#drop_list = [32000, 33000, 34000] # For burst loss
if sequence in drop_list and self.dropped_count < len(drop_list):
self.trace("Manually dropping packet %d" % sequence)
packet.drop = True
if packet.drop:
# manually drop packets
self.dropped_count += 1
self.recordPacketDropped(Sim.scheduler.current_time(),
packet.sequence)
else:
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.sequence))
self.transport.send_packet(packet)
self.recordPacketSent(Sim.scheduler.current_time(),
packet.sequence)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
def slow_start(self, duplicate_acks=False):
# if the AIAD setting is turned on
if self.aiad:
self.window -= self.mss
self.state = 1
# otherwise do regular recovery
else:
if duplicate_acks and self.fast_recovery:
# If using fast recovery and three duplicate acks are detected,
# set the window to self.aimdc (AIMD constant) of the original and
# keep going with additive increase
self.window = int(
round(self.window * self.aimdc / self.mss) * self.mss)
self.state = 1
else:
# Otherwise reset the window to 1 mss and use slow start
self.window = self.mss
self.state = 0
self.recordWindow()
def increaseWindow(self, packet):
# Increase the window
if self.state == 0:
# Slow Start
self.window += packet.ack_packet_length
self.trace(
"Slow Start - Incremented window by %d. New window size: %d" %
(packet.ack_packet_length, self.window))
# If the window equals or exceeds the threshold, stop slow start
if self.window >= self.threshold:
self.trace(
"Hit threshold of %d. Switching from slow start to additive increase"
% self.threshold)
self.state = 1
elif self.state == 1:
#Additive increase
# "increment cwnd by MSS*b/cwnd"
increment = self.mss * packet.ack_packet_length / self.window
self.window += increment
self.trace(
"Additive Increase - Incremented window by %d. New window size: %d"
% (increment, self.window))
self.recordWindow()
def calculateRTO(self, packet):
# Calculate Sample RTT
sample_rtt = Sim.scheduler.current_time() - packet.sent_time
#self.trace("sample round trip time %f" % sample_rtt)
# Calculate the new estimated RTT
alpha = 0.125
if not self.estimated_rtt:
self.estimated_rtt = sample_rtt
else:
self.estimated_rtt = (
1 - alpha) * self.estimated_rtt + alpha * sample_rtt
# Calculate the deviation of the sample RTT
beta = 0.25
if not self.deviation_rtt:
self.deviation_rtt = self.estimated_rtt / 2
else:
self.deviation_rtt = (1 - beta) * self.deviation_rtt + beta * abs(
sample_rtt - self.estimated_rtt)
# Calculate the Retransmission Timeout (RTO)
self.timeout = self.estimated_rtt + 4 * self.deviation_rtt
#self.trace("changed the timeout to %f" % self.timeout)
def slideWindow(self, packet):
self.sequence = packet.ack_number
self.send_buffer.slide(packet.ack_number)
def sendNextBatch(self):
self.cancel_timer()
if self.send_buffer.outstanding() or self.send_buffer.available():
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
self.queue_packets()
def handle_ack(self, packet):
''' Handle an incoming ACK. '''
self.trace("received TCP ACK for %d" % packet.ack_number)
# For sequence chart plotting
self.recordAckReceived(Sim.scheduler.current_time(), packet.ack_number)
# Calculate RTO
self.calculateRTO(packet)
# Watch for three duplicate acks
if self.last_ack != packet.ack_number:
# If a new ack is received
self.last_ack = packet.ack_number
self.same_ack_count = 1
self.increaseWindow(packet)
self.slideWindow(packet)
self.sendNextBatch()
else:
# A duplicate ack has been received
self.same_ack_count += 1
if self.same_ack_count > 3:
# When the fourth ack with the same number is received (3 duplicates)
self.trace(
"Three duplicate ACKs. Ignoring duplicate ACKs for same sequence number"
)
self.same_ack_count = -100
self.threshold = max(self.window / 2, self.mss)
self.trace("Set new threshold to %d" % self.threshold)
self.cancel_timer()
self.retransmit({}, duplicate_acks=True)
def retransmit(self, event, duplicate_acks=False):
''' Retransmit data. '''
if duplicate_acks:
self.trace("%s (%d) retransmission timer fired" %
(self.node.hostname, self.source_address))
else:
self.trace(
"%s (%d) Three duplicate acks detected. Retransmitting immediately"
% (self.node.hostname, self.source_address))
self.trace("Slow start initiated")
self.slow_start(duplicate_acks=duplicate_acks)
packet_data = self.send_buffer.resend(self.mss)
self.send_packet(packet_data[0], packet_data[1])
self.timeout = min(self.timeout * 2,
3600) # should never exceed an hour
self.trace("doubled the timeout to %f" % self.timeout)
# CANCEL TIMER BEFORE SETTING A NEW ONE?
self.cancel_timer()
open_window_space = self.window - self.send_buffer.outstanding()
if self.send_buffer.outstanding() or self.send_buffer.available():
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
def cancel_timer(self):
''' Cancel the timer. '''
if not self.timer:
return
try:
Sim.scheduler.cancel(self.timer)
except ValueError:
self.trace("Tried to cancel same timer twice")
self.timer = None
''' Receiver '''
def handle_data(self, packet):
''' Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK.'''
self.queueing_delay_list.append(packet.queueing_delay)
self.trace("%s (%d) received TCP segment from %d for %d" %
(self.node.hostname, packet.destination_address,
packet.source_address, packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
data = self.receive_buffer.get()
self.ack = len(data[0]) + data[1]
self.app.receive_data(data[0])
self.send_ack(packet.sent_time, packet.length)
self.increase_packet_count()
def increase_packet_count(self):
t = Sim.scheduler.current_time()
t = "{0:0.1f}".format(math.floor(t * 10) / 10.0)
c = self.packets_received.get(t)
if not c:
self.packets_received[t] = 0
self.packets_received[t] += 1
def send_ack(self, packet_sent_time=0, packet_length=0):
''' Send an ack. '''
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,
ack_number=self.ack,
sent_time=packet_sent_time,
ack_packet_length=packet_length)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
""" A TCP connection between two hosts."""
def __init__(self,
transport,
source_address,
source_port,
destination_address,
destination_port,
app=None,
window=1000,
fastRetransmit=False):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
# -- Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# -- Receiver functionality
self.fastRetransmit = fastRetransmit
self.sameAcks = 0
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
def trace(self, message):
""" Print debugging messages. """
Sim.trace("TCP", message)
def receive_packet(self, packet):
""" Receive a packet from the network layer. """
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
# make sure timer hasn't been added already
def send(self, data):
""" Send data on the connection. Called by the application. This
code currently sends all data immediately. """
self.send_buffer.put(data)
self.sendFullWindow()
self.maybe_start_timer()
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,
ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.sequence))
self.transport.send_packet(packet)
# TODO: might have broken this by commenting it out.
# # set a timer
# if not self.timer:
# self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def handle_ack(self, packet):
""" Handle an incoming ACK. """
self.trace("%s (%d) received TCP ACK from %d for %d current seq %d" %
(self.node.hostname, packet.destination_address,
packet.source_address, packet.ack_number, self.sequence))
if packet.ack_number > self.sequence:
self.sequence = packet.ack_number
self.cancel_timer()
self.send_buffer.slide(self.sequence)
self.maybe_start_timer()
self.sendFullWindow()
self.sameAcks = 1
elif self.fastRetransmit and packet.ack_number == self.sequence:
self.sameAcks += 1
if self.sameAcks == 4:
self.trace('retransmitting')
self.cancel_timer()
self.resetWindow()
def resetWindow(self):
""" resets the window and sends all data available in the window """
(data, sequence) = self.send_buffer.resend(self.mss)
if len(data) > 0:
self.maybe_start_timer()
self.send_packet(data, sequence)
def sendFullWindow(self):
""" sends all data left in the window """
while self.send_buffer.outstanding() < self.window:
(data, seq) = self.send_buffer.get(self.mss)
if len(data) == 0:
return
self.send_packet(data, seq)
# modify this code
def retransmit(self, event):
""" Retransmit data. """
self.trace("%s (%d) retransmission timer fired" %
(self.node.hostname, self.source_address))
self.timer = None
self.resetWindow()
# should work
def cancel_timer(self):
""" Cancel the timer. """
self.trace('canceling timer')
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
def maybe_start_timer(self):
""" Starts timer if it doesn't exist """
self.trace('maybe starting timer')
if not self.timer and self.send_buffer.dataRemaining():
self.trace('starting timer')
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
else:
self.trace('timer not started')
''' Receiver '''
# get this to work correctly
def handle_data(self, packet):
""" Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK."""
self.trace("%s (%d) received TCP segment from %d for %d" %
(self.node.hostname, packet.destination_address,
packet.source_address, packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
(data, seq) = self.receive_buffer.get()
if len(data) > 0:
self.app.receive_data(data)
self.ack += len(data)
self.send_ack()
# should work
def send_ack(self):
""" Send an ack. """
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,
ack_number=self.ack)
# send the packet
self.transport.send_packet(packet)
self.trace("%s (%d) sending TCP ACK to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.ack_number))
class TCP(Connection):
""" A TCP connection between two hosts."""
def __init__(
self,
transport,
source_address,
source_port,
destination_address,
destination_port,
app=None,
window=1000,
dynamic_rto=True,
type="Tahoe",
window_size_plot=False,
sequence_plot=False,
receiver_flow_plot=False,
):
Connection.__init__(self, transport, source_address, source_port, destination_address, destination_port, app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = default_mss
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = default_mss
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
self.threshold = 100000
self.ack_received_count = {}
self.wait_for_timeout = False
self.reno_fast_recovery = type == "Reno"
# constants
self.k = 4
self.g = 0.1
self.alpha = 1 / 8
self.beta = 1 / 4
self.dynamic_rto = dynamic_rto
self.rto = 3
self.srtt = None
self.rttvar = None
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
self.window_size_plot = window_size_plot
self.sequence_plot = sequence_plot
self.receiver_flow_plot = receiver_flow_plot
self.decisecond_received = 0
self.decisecond_bytes = []
def trace(self, message):
""" Print debugging messages. """
Sim.trace("TCP", message)
def receive_packet(self, packet):
""" Receive a packet from the network layer. """
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
""" Sender """
def send(self, data):
""" Send data on the connection. Called by the application. This
code currently sends all data immediately. """
self.send_buffer.put(data)
self.send_packets_if_possible()
def send_packets_if_possible(self):
# if self.send_buffer.outstanding() < self.window:
while self.send_buffer.outstanding() < self.window and self.send_buffer.available():
data_length = min(self.window - self.send_buffer.outstanding(), self.mss)
data_tuple = self.send_buffer.get(data_length)
data = data_tuple[0]
self.sequence = data_tuple[1]
self.send_packet(data, self.sequence)
def send_packet(self, data, sequence):
packet = TCPPacket(
source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,
ack_number=self.ack,
)
packet.created = Sim.scheduler.current_time()
# Store data for plotting
if self.sequence_plot:
self.app.add_plot_data(Sim.scheduler.current_time(), sequence, "Transmitted")
# send the packet
self.trace(
"%s (%d) sending TCP segment to %d for %d"
% (self.node.hostname, self.source_address, self.destination_address, packet.sequence)
)
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.rto, event="retransmit", handler=self.retransmit)
def handle_ack(self, packet):
""" Handle an incoming ACK. """
r = Sim.scheduler.current_time() - packet.created
if not self.srtt and not self.rttvar:
self.srtt = r
self.rttvar = r / 2
else:
self.rttvar = (1 - self.beta) * self.rttvar + (self.beta * abs(self.srtt - r))
self.srtt = (1 - self.alpha) * self.srtt + (self.alpha * r)
self.rto = self.srtt + max(self.g, self.k * self.rttvar)
self.trace(
"%s (%d) receiving TCP ACK from %d for %d"
% (self.node.hostname, self.source_address, self.destination_address, packet.ack_number)
)
self.cancel_timer()
# Slide the buffer and get the number of new bytes acked - only if the ack number is >= the base of the send buffer
old_unacked = self.send_buffer.outstanding()
if packet.ack_number < self.send_buffer.base:
return
self.send_buffer.slide(packet.ack_number)
new_unacked = self.send_buffer.outstanding()
new_acked_data = max(old_unacked - new_unacked, 0)
if packet.ack_number not in self.ack_received_count:
self.ack_received_count[packet.ack_number] = 0
self.ack_received_count[packet.ack_number] += 1
# If this is the fourth ack with the same number that you are receiving, fast retransmit
if self.ack_received_count[packet.ack_number] == 4 and not self.wait_for_timeout:
# Sim.scheduler.cancel(self.timer)
self.wait_for_timeout = True
self.retransmit(True, True)
# Otherwise, if the window is less than the threshold, slow start increase the window size
elif self.window < self.threshold:
self.window += new_acked_data
# Store data for plotting
if self.sequence_plot:
self.app.add_plot_data(Sim.scheduler.current_time(), packet.ack_number, "Acked")
# Otherwise, additive increase the window size
else:
self.window += (self.mss * new_acked_data) / self.window
if self.sequence_plot:
self.app.add_plot_data(Sim.scheduler.current_time(), packet.ack_number, "Acked")
if self.window_size_plot:
self.app.add_plot_data(Sim.scheduler.current_time(), self.window, "WindowSize")
self.send_packets_if_possible()
if self.send_buffer.outstanding() and not self.timer:
self.timer = Sim.scheduler.add(delay=self.rto, event="retransmit", handler=self.retransmit)
def retransmit(self, event, duplicate_ack=False):
""" Retransmit data. """
self.threshold = max(self.threshold - self.mss, self.mss)
self.window = self.mss
self.timer = None
self.trace("%s (%d) entering fast retransmission" % (self.node.hostname, self.source_address))
data_tuple = self.send_buffer.resend(self.window) # TODO: Make this bigger, I think
data = data_tuple[0]
if data:
self.sequence = data_tuple[1]
# Store data for plotting
if self.sequence_plot:
self.app.add_plot_data(Sim.scheduler.current_time(), self.sequence, "Dropped")
self.timer = Sim.scheduler.add(delay=self.rto, event="retransmit", handler=self.retransmit)
self.send_packet(data, self.sequence)
def cancel_timer(self):
""" Cancel the timer. """
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
""" Receiver """
def handle_data(self, packet):
""" Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK."""
self.trace(
"%s (%d) received TCP segment from %d for %d"
% (self.node.hostname, packet.destination_address, packet.source_address, packet.sequence)
)
self.receive_buffer.put(packet.body, packet.sequence)
# For throughput
self.decisecond_received += len(packet.body)
data_tuple = self.receive_buffer.get()
data = data_tuple[0]
sequence = data_tuple[1]
if data:
self.app.receive_data(data)
self.ack = sequence + len(data)
self.send_ack(packet.created)
def spur_plot_data_submission(self):
if not self.receiver_flow_plot:
return
self.decisecond_bytes.append(self.decisecond_received)
self.decisecond_received = 0
if len(self.decisecond_bytes) >= 10:
total_bytes_previous_second = sum(
self.decisecond_bytes[(len(self.decisecond_bytes) - 10) : len(self.decisecond_bytes)]
)
else:
total_bytes_previous_second = sum(self.decisecond_bytes)
self.app.add_plot_data(Sim.scheduler.current_time(), total_bytes_previous_second, "ReceiverRate")
def send_ack(self, created):
""" Send an ack. """
packet = TCPPacket(
source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,
ack_number=self.ack,
)
packet.created = created
# send the packet
self.trace(
"%s (%d) sending TCP ACK to %d for %d"
% (self.node.hostname, self.source_address, self.destination_address, packet.ack_number)
)
self.transport.send_packet(packet)
class TCP(Connection):
""" A TCP connection between two hosts."""
def __init__(self, transport, source_address, source_port,
destination_address, destination_port, app=None, window=1000,drop=[]):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
# -- Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# plot sequence numbers
self.plot_sequence_header()
# plot congestion window headers
self.plot_window_header()
# packets to drop
self.drop = drop
self.dropped = []
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# RTO calculation variables
self.rto = 1
self.srtt = 0
self.rttvar = 0
# Variables for handling fast retransmit
self.fast_enable = False
self.last_ack = 0
self.same_ack_count = 0
self.fast_retransmitted = False
# Congestion control
self.threshold = 100000
self.increment = 0
# -- Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
def trace(self, message):
""" Print debugging messages. """
Sim.trace("TCP", message)
def plot_sequence_header(self):
if self.node.hostname =='n1':
Sim.plot('sequence.csv','Time,Sequence Number,Event\n')
def plot_sequence(self,sequence,event):
if self.node.hostname =='n1':
Sim.plot('sequence.csv','%s,%s,%s\n' % (Sim.scheduler.current_time(),sequence,event))
def plot_window_header(self):
if self.node.hostname == 'n1':
Sim.plot('cwnd.csv','Time,Congestion Window,Threshold,Event\n')
def plot_window(self, event):
if self.node.hostname == 'n1':
Sim.plot('cwnd.csv', '%s,%s,%s,%s\n' % (Sim.scheduler.current_time(), self.window, self.threshold, event))
def receive_packet(self, packet):
""" Receive a packet from the network layer. """
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle networks
self.handle_data(packet)
def set_fast_retransmit_enabled(self, val):
self.fast_enable = val
''' Sender '''
def send(self, data):
""" Send networks on the connection. Called by the application. This code puts the
networks to send in a send buffer that handles when the networks will be sent."""
# Put the networks in the send buffer
self.send_buffer.put(data)
# Check for available bytes to send
while self.send_buffer.available() != 0 and self.send_buffer.outstanding() < self.window:
# Only send as many bytes as the window allows
send_data, sequence = self.send_buffer.get(self.mss)
self.send_packet(send_data, sequence)
# set a timer
if self.timer is None:
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence, ack_number=self.ack)
if sequence in self.drop and not sequence in self.dropped:
self.dropped.append(sequence)
self.plot_sequence(sequence,'drop')
self.trace("%s (%d) dropping TCP segment to %d for %d" % (
self.node.hostname, self.source_address, self.destination_address, packet.sequence))
return
# send the packet
self.plot_sequence(sequence,'send')
self.trace("%s (%d) sending TCP segment to %d for %d" % (
self.node.hostname, self.source_address, self.destination_address, packet.sequence))
self.transport.send_packet(packet)
# set a timer
if self.timer is None:
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def handle_ack(self, packet):
""" Handle an incoming ACK. """
self.plot_sequence(packet.ack_number - 1000,'ack')
self.trace("%s (%d) received ACK from %d for %d" % (
self.node.hostname, packet.destination_address, packet.source_address, packet.ack_number))
# Handle fast retransmit
if self.fast_enable:
if packet.ack_number == self.last_ack:
self.same_ack_count += 1
if self.same_ack_count == 3 and not self.fast_retransmitted:
self.fast_retransmit(packet)
return
else:
# Reset fast retransmit variables
self.same_ack_count = 0
self.last_ack = packet.ack_number
self.fast_retransmitted = False
# Congestion control
if self.window >= self.threshold:
self.additive_increase(packet.ack_number - self.sequence)
else:
self.slow_start(packet.ack_number - self.sequence)
# Update the send buffer
self.sequence = packet.ack_number
self.send_buffer.slide(packet.ack_number)
# Send additional bytes from the send buffer if there are any
while self.send_buffer.available() != 0 and self.send_buffer.outstanding() < self.window:
# Only send as many bytes as the window allows
send_data, sequence = self.send_buffer.get(self.mss)
self.send_packet(send_data, sequence)
# Calculate the SRTT and RTTVAR
if self.srtt == 0:
# First estimate
self.srtt = Sim.scheduler.current_time() - packet.created
self.rttvar = self.srtt / 2.0
else:
r = Sim.scheduler.current_time() - packet.created
alpha = 0.125
beta = 0.25
self.rttvar = (1 - beta) * self.rttvar + beta * abs(self.srtt - r)
self.srtt = (1 - alpha) * self.srtt + alpha * r
# Update the RTO
rto = self.srtt + 4 * self.rttvar
self.rto = rto if rto >= 1.0 else 1.0
self.cancel_timer()
if self.send_buffer.outstanding() != 0:
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def fast_retransmit(self, packet):
""" Retransmit networks. """
self.trace("%s (%d) sending fast retransmit to %d for %d" % (
self.node.hostname, packet.destination_address, packet.source_address, packet.ack_number))
self.cancel_timer()
self.threshold = max(self.window // 2, self.mss)
self.threshold = self.threshold - (self.threshold % self.mss)
self.window = self.mss
self.increment = 0
self.plot_window('fast retransmit')
data, sequence = self.send_buffer.resend(self.window)
if len(data) == 0:
return
self.send_packet(data, sequence)
if self.timer is None:
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
self.fast_retransmitted = True
def retransmit(self, event):
""" Retransmit networks. """
self.trace("%s (%d) retransmission timer fired" % (self.node.hostname, self.source_address))
self.threshold = max(self.window // 2, self.mss)
self.threshold = self.threshold - (self.threshold % self.mss)
self.window = self.mss
self.increment = 0
self.plot_window('retransmission')
data, sequence = self.send_buffer.resend(self.window)
# Handle the case when we get a misfire on retransmission and their isn't any data left
# in the send buffer
if len(data) == 0:
self.cancel_timer()
return
self.send_packet(data, sequence)
self.timer = Sim.scheduler.add(delay=self.rto, event='retransmit', handler=self.retransmit)
def slow_start(self, bytes):
self.trace("%s (%d) incrementing slow start" % (self.node.hostname, self.source_address))
self.window = self.window + (bytes if bytes <= self.mss else self.mss)
self.plot_window('slow start')
def additive_increase(self, bytes):
self.increment = self.increment + bytes * self.mss / self.window
if self.increment >= self.mss:
self.trace("%s (%d) incrementing additive increase" % (self.node.hostname, self.source_address))
self.window = self.window + self.mss
self.increment = self.increment - self.mss
self.plot_window('additive increase')
def cancel_timer(self):
""" Cancel the timer. """
if self.timer is None:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self, packet):
""" Handle incoming networks. This code currently gives all networks to
the application, regardless of whether it is in order, and sends
an ACK."""
self.trace("%s (%d) received TCP segment from %d for %d" % (
self.node.hostname, packet.destination_address, packet.source_address, packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
data, start_sequence = self.receive_buffer.get()
self.app.receive_data(data)
self.ack = start_sequence + len(data)
self.send_ack()
def send_ack(self):
""" Send an ack. """
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence, ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" % (
self.node.hostname, self.source_address, self.destination_address, packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
''' A TCP connection between two hosts.'''
def __init__(self,transport,source_address,source_port,
destination_address,destination_port,app=None,window=1000,dynamic_rto=True):
Connection.__init__(self,transport,source_address,source_port,
destination_address,destination_port,app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# constants
self.k = 4
self.g = .1
self.alpha = 1/8
self.beta = 1/4
self.dynamic_rto = dynamic_rto
self.rto = 3
self.srtt = None
self.rttvar = None
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
def trace(self,message):
''' Print debugging messages. '''
Sim.trace("TCP",message)
def receive_packet(self,packet):
''' Receive a packet from the network layer. '''
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self,data):
''' Send data on the connection. Called by the application. This
code currently sends all data immediately. '''
self.send_buffer.put(data)
self.send_packets_if_possible()
def send_packets_if_possible(self):
# if self.send_buffer.outstanding() < self.window:
while self.send_buffer.outstanding() < self.window and self.send_buffer.available():
data_length = min(self.window - self.send_buffer.outstanding(), self.mss)
data_tuple = self.send_buffer.get(data_length)
data = data_tuple[0]
self.sequence = data_tuple[1]
self.send_packet(data,self.sequence)
def send_packet(self,data,sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,ack_number=self.ack)
packet.created = Sim.scheduler.current_time()
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.rto, event='retransmit', handler=self.retransmit)
def handle_ack(self,packet):
''' Handle an incoming ACK. '''
r = Sim.scheduler.current_time() - packet.created
if not self.srtt and not self.rttvar:
self.srtt = r
self.rttvar = r / 2
else:
self.rttvar = (1 - self.beta) * self.rttvar + (self.beta * abs(self.srtt - r))
self.srtt = (1 - self.alpha) * self.srtt + (self.alpha * r)
self.rto = self.srtt + max(self.g, self.k * self.rttvar)
self.trace("%s (%d) receiving TCP ACK from %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.ack_number))
self.cancel_timer()
self.send_buffer.slide(packet.ack_number)
self.send_packets_if_possible()
if self.send_buffer.outstanding() and not self.timer:
self.timer = Sim.scheduler.add(delay=self.rto, event='retransmit', handler=self.retransmit)
def retransmit(self,event):
''' Retransmit data. '''
self.timer = None
self.trace("%s (%d) retransmission timer fired" % (self.node.hostname,self.source_address))
data_tuple = self.send_buffer.resend(self.mss)
data = data_tuple[0]
if data:
self.sequence = data_tuple[1]
if self.dynamic_rto:
self.timer = Sim.scheduler.add(delay=self.rto, event='retransmit', handler=self.retransmit)
else:
self.timer = Sim.scheduler.add(delay=self.rto, event='retransmit', handler=self.retransmit)
self.send_packet(data, self.sequence)
def cancel_timer(self):
''' Cancel the timer. '''
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self,packet):
''' Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK.'''
self.trace("%s (%d) received TCP segment from %d for %d" % (self.node.hostname,packet.destination_address,packet.source_address,packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
data_tuple = self.receive_buffer.get()
data = data_tuple[0]
sequence = data_tuple[1]
if data:
self.app.receive_data(data)
self.ack = sequence + len(data)
self.send_ack(packet.created)
def send_ack(self, created):
''' Send an ack. '''
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,ack_number=self.ack)
packet.created = created
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
""" A TCP connection between two hosts."""
def __init__(self,
transport,
source_address,
source_port,
destination_address,
destination_port,
app=None,
window=1000,
fast_retransmit=False):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
# -- Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
self.fast_retransmit = fast_retransmit
# -- Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
self.current_ack_number = None
self.current_ack_counter = 0
self.total_packets_received = 0
self.total_queueing_delay = 0
def trace(self, message):
""" Print debugging messages. """
Sim.trace("TCP", message)
def receive_packet(self, packet):
""" Receive a packet from the network layer. """
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self, data):
""" Send data on the connection. Called by the application. This
code currently sends all data immediately. """
self.send_buffer.put(data)
self.send_max_possible()
def send_max_possible(self):
if self.send_buffer.available() == 0:
return
if self.send_buffer.outstanding() >= self.window:
return
data, sequence = self.send_buffer.get(self.mss)
self.send_packet(data, sequence)
self.send_max_possible()
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,
ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.start_timer()
def handle_ack(self, packet):
""" Handle an incoming ACK. """
self.trace(
"%s (%d) handling ACK %d" %
(self.node.hostname, self.source_address, packet.ack_number))
if self.fast_retransmit:
if packet.ack_number == self.current_ack_number:
self.current_ack_counter += 1
else:
self.current_ack_number = packet.ack_number
self.current_ack_counter = 1
if self.current_ack_counter == 4:
self.current_ack_counter += 1
self.cancel_timer()
self.retransmit('retransmit')
return
if packet.ack_number > self.sequence:
self.sequence = packet.ack_number
self.send_buffer.slide(self.sequence)
self.cancel_timer()
self.start_timer()
self.send_max_possible()
def retransmit(self, event):
""" Retransmit data. """
if (self.send_buffer.outstanding() == 0
and self.send_buffer.available() == 0):
return
data, sequence = self.send_buffer.resend(self.mss)
self.send_packet(data, sequence)
self.trace("%s (%d) retransmission timer fired" %
(self.node.hostname, self.source_address))
self.start_timer()
def start_timer(self):
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
def cancel_timer(self):
""" Cancel the timer. """
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self, packet):
""" Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK."""
self.total_packets_received += 1
self.total_queueing_delay += packet.queueing_delay
self.trace("%s (%d) received TCP segment from %d for %d" %
(self.node.hostname, packet.destination_address,
packet.source_address, packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
data, start = self.receive_buffer.get()
self.app.receive_data(data)
self.ack = start + len(data)
self.send_ack()
def send_ack(self):
""" Send an ack. """
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,
ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
''' A TCP connection between two hosts.'''
def __init__(self,transport,source_address,source_port,
destination_address,destination_port,app=None,window=1000,
threshold=100000,fast_recovery=False):
Connection.__init__(self,transport,source_address,source_port,
destination_address,destination_port,app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time (cwnd)
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# Round trip time in seconds
self.estimated_rtt = None
# Deviation of sample rtt from estimated rtt
self.deviation_rtt = None
# State determines slow start vs. additive increase
# 0 = slow start
# 1 = additive increase
self.state = 0
# Threshold for slow start
self.threshold = threshold
self.trace("Threshold starting at %d" % self.threshold)
# Same ack count (used for calculating three duplicate acks)
self.same_ack_count = 0
# Most recent ack (used for calculating three duplicate acks)
self.last_ack = None
# Make sure settings start with slow start
self.window = self.mss
# Used when dropping certain packets
self.dropped_count = 0
# Fast Recovery (Reno)
self.fast_recovery=fast_recovery
### Used to make TCP Sequence Graphs
self.x = []
self.y = []
self.dropX = []
self.dropY = []
self.ackX = []
self.ackY = []
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
# a list of all the queuing delays from the sender to receiver
self.queueing_delay_list = []
def trace(self,message):
''' Print debugging messages. '''
Sim.trace("TCP",message)
def receive_packet(self,packet):
''' Receive a packet from the network layer. '''
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
# Record packets sent for plotting purposes
def recordPacketSent(self, time, sequence):
self.x.append(time)
self.y.append((sequence / 1000) % 50)
# Record packets dropped for plotting purposes
def recordPacketDropped(self, time, sequence):
self.dropX.append(time)
self.dropY.append((sequence / 1000) % 50)
# Record acks received for plotting purposes
def recordAckReceived(self, time, sequence):
self.ackX.append(time)
self.ackY.append((sequence / 1000) % 50)
def send(self,data):
''' Send data on the connection. Called by the application. This
code uses the SendBuffer to send incrementally '''
self.send_buffer.put(data)
self.queue_packets()
def queue_packets(self):
''' Send the next set of packets if there's any to send. Limit based
on window size and the number of outstanding packets '''
while True:
if self.send_buffer.available() <= 0:
break
open_window_space = self.window - self.send_buffer.outstanding()
if open_window_space <= 0:
break
# Send nice MSS sized packets
if open_window_space < self.mss:
break
packet_size = min(open_window_space, self.mss)
packet_data = self.send_buffer.get(packet_size)
self.send_packet(packet_data[0], packet_data[1])
def send_packet(self,data,sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,ack_number=self.ack,
sent_time=Sim.scheduler.current_time())
# Forced Loss, loss, AIMD dropped packets
drop_list = []
#drop_list = [32000] # For a single loss
#drop_list = [32000, 33000, 34000] # For burst loss
if sequence in drop_list and self.dropped_count < len(drop_list):
self.trace("Manually dropping packet %d" % sequence)
packet.drop = True
if packet.drop:
# manually drop packets
self.dropped_count += 1
self.recordPacketDropped(Sim.scheduler.current_time(), packet.sequence)
else:
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.sequence))
self.transport.send_packet(packet)
self.recordPacketSent(Sim.scheduler.current_time(), packet.sequence)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def slow_start(self, duplicate_acks=False):
if duplicate_acks and self.fast_recovery:
# If using fast recovery and three duplicate acks are detected,
# set the window to half the original and
# keep going with additive increase
self.window = int(round(self.window/2 / self.mss) * self.mss)
self.state = 1
else:
# Otherwise reset the window to 1 mss and use slow start
self.window = self.mss
self.state = 0
def increaseWindow(self,packet):
# Increase the window
if self.state == 0:
# Slow Start
self.window += packet.ack_packet_length
self.trace("Slow Start - Incremented window by %d. New window size: %d" % (packet.ack_packet_length, self.window))
# If the window equals or exceeds the threshold, stop slow start
if self.window >= self.threshold:
self.trace("Hit threshold of %d. Switching from slow start to additive increase" % self.threshold)
self.state = 1
elif self.state == 1:
#Additive increase
# "increment cwnd by MSS*b/cwnd"
increment = self.mss * packet.ack_packet_length / self.window
self.window += increment
self.trace("Additive Increase - Incremented window by %d. New window size: %d" % (increment, self.window))
def calculateRTO(self, packet):
# Calculate Sample RTT
sample_rtt = Sim.scheduler.current_time() - packet.sent_time
#self.trace("sample round trip time %f" % sample_rtt)
# Calculate the new estimated RTT
alpha = 0.125
if not self.estimated_rtt:
self.estimated_rtt = sample_rtt
else:
self.estimated_rtt = (1 - alpha) * self.estimated_rtt + alpha * sample_rtt
# Calculate the deviation of the sample RTT
beta = 0.25
if not self.deviation_rtt:
self.deviation_rtt = self.estimated_rtt/2
else:
self.deviation_rtt = (1 - beta) * self.deviation_rtt + beta * abs(sample_rtt - self.estimated_rtt)
# Calculate the Retransmission Timeout (RTO)
self.timeout = self.estimated_rtt + 4 * self.deviation_rtt
#self.trace("changed the timeout to %f" % self.timeout)
def slideWindow(self,packet):
self.sequence = packet.ack_number
self.send_buffer.slide(packet.ack_number)
def sendNextBatch(self):
self.cancel_timer()
if self.send_buffer.outstanding() or self.send_buffer.available():
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
self.queue_packets()
def handle_ack(self,packet):
''' Handle an incoming ACK. '''
self.trace("received TCP ACK for %d" % packet.ack_number)
# For sequence chart plotting
self.recordAckReceived(Sim.scheduler.current_time(), packet.ack_number)
# Calculate RTO
self.calculateRTO(packet)
# Watch for three duplicate acks
if self.last_ack != packet.ack_number:
# If a new ack is received
self.last_ack = packet.ack_number
self.same_ack_count = 1
self.increaseWindow(packet)
self.slideWindow(packet)
self.sendNextBatch()
else:
# A duplicate ack has been received
self.same_ack_count += 1
if self.same_ack_count > 3:
# When the fourth ack with the same number is received (3 duplicates)
self.trace("Three duplicate ACKs. Ignoring duplicate ACKs for same sequence number")
self.same_ack_count = -100
self.threshold = max(self.window/2, self.mss)
self.trace("Set new threshold to %d" % self.threshold)
self.cancel_timer()
self.retransmit({},duplicate_acks=True)
def retransmit(self,event,duplicate_acks=False):
''' Retransmit data. '''
if duplicate_acks:
self.trace("%s (%d) retransmission timer fired" % (self.node.hostname,self.source_address))
else:
self.trace("%s (%d) Three duplicate acks detected. Retransmitting immediately" % (self.node.hostname,self.source_address))
self.trace("Slow start initiated")
self.slow_start(duplicate_acks=duplicate_acks)
packet_data = self.send_buffer.resend(self.mss)
self.send_packet(packet_data[0], packet_data[1])
self.timeout = min(self.timeout * 2, 3600) # should never exceed an hour
self.trace("doubled the timeout to %f" % self.timeout)
# CANCEL TIMER BEFORE SETTING A NEW ONE?
self.cancel_timer()
open_window_space = self.window - self.send_buffer.outstanding()
if self.send_buffer.outstanding() or self.send_buffer.available():
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def cancel_timer(self):
''' Cancel the timer. '''
if not self.timer:
return
try:
Sim.scheduler.cancel(self.timer)
except ValueError:
self.trace("Tried to cancel same timer twice")
self.timer = None
''' Receiver '''
def handle_data(self,packet):
''' Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK.'''
self.queueing_delay_list.append(packet.queueing_delay)
self.trace("%s (%d) received TCP segment from %d for %d" % (self.node.hostname,packet.destination_address,packet.source_address,packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
data = self.receive_buffer.get()
self.ack = len(data[0]) + data[1]
self.app.receive_data(data[0])
self.send_ack(packet.sent_time, packet.length)
def send_ack(self, packet_sent_time=0, packet_length=0):
''' Send an ack. '''
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,ack_number=self.ack,
sent_time=packet_sent_time,ack_packet_length=packet_length)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
""" A TCP connection between two hosts."""
def __init__(self,
transport,
source_address,
source_port,
destination_address,
destination_port,
app=None,
drop=[],
fast_retransmit=False,
measure=False):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
# -- Sender functionality
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# initial cwnd is equal to 1mss
self.cwnd = float(self.mss)
# boolean flag that indicates if in slow start or additive increase
self.slow_start = True
# When cwnd >= ss_thresh, slow start ends
self.ss_thresh = 100000
if self.node.hostname == 'n1':
self.trace("Entering Slow Start: SS Thresh = %s" %
(self.ss_thresh))
# Tracks additive increase - determines when to add another MSS to cwnd
self.cwnd_inc = 0
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# plot sequence numbers
self.plot_sequence_header()
self.plot_cwnd_header()
self.plot_cwnd()
# packets to drop
self.drop = drop
self.dropped = []
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# -- Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
self.fast_retransmit = fast_retransmit
self.last_ack = 0
self.last_ack_count = 0
def trace(self, message):
""" Print debugging messages. """
Sim.trace("TCP", message)
def plot_sequence_header(self):
if self.node.hostname == 'n1':
Sim.plot('sequence.csv', 'Time,Sequence Number,Event\n')
def plot_sequence(self, sequence, event):
if self.node.hostname == 'n1':
Sim.plot(
'sequence.csv',
'%s,%s,%s\n' % (Sim.scheduler.current_time(), sequence, event))
def plot_cwnd_header(self):
if self.node.hostname == 'n1':
Sim.plot('cwnd.csv', 'Time,Congestion Window\n')
def plot_cwnd(self):
if self.node.hostname == 'n1':
Sim.plot(
'cwnd.csv',
'%s,%s\n' % (Sim.scheduler.current_time(), int(self.cwnd)))
def receive_packet(self, packet):
""" Receive a packet from the network layer. """
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self, data):
""" Send data on the connection. Called by the application."""
self.send_buffer.put(data)
self.send_window()
def send_window(self):
while self.send_buffer.outstanding(
) < self.cwnd and self.send_buffer.available() > 0:
(packet_data, self.sequence) = self.send_buffer.get(self.mss)
self.send_packet(packet_data, self.sequence)
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,
ack_number=self.ack)
if sequence in self.drop and not sequence in self.dropped:
self.dropped.append(sequence)
self.plot_sequence(sequence, 'drop')
self.trace("%s (%d) dropping TCP segment to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.sequence))
self.trace("PACKET DROPPED CWND IS %s\n" % (self.cwnd))
return
# send the packet
self.plot_sequence(sequence, 'send')
self.trace("%s (%d) sending TCP segment to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.start_retransmit_timer(self.timeout)
def handle_ack(self, packet):
""" Handle an incoming ACK. """
self.plot_sequence(packet.ack_number - 1000, 'ack')
prev_out = self.send_buffer.outstanding()
self.send_buffer.slide(packet.ack_number)
bytes_acked = prev_out - self.send_buffer.outstanding()
self.trace("%s (%d) received ACK from %d for %d. %d bytes ACKed" %
(self.node.hostname, packet.destination_address,
packet.source_address, packet.ack_number, bytes_acked))
if self.fast_retransmit:
if self.last_ack == packet.ack_number:
self.last_ack_count += 1
if self.last_ack_count == 4:
self.retransmit(None)
elif packet.ack_number > self.last_ack:
self.last_ack = packet.ack_number
self.last_ack_count = 1
if bytes_acked > 0:
if self.slow_start:
self.cwnd += self.mss
self.plot_cwnd()
if self.cwnd == self.ss_thresh:
self.slow_start = False
self.trace("Entering Additive Increase: CWND = %s" %
(self.cwnd))
else:
self.cwnd_inc += self.mss * bytes_acked / self.cwnd
if self.cwnd_inc > self.mss:
self.cwnd += self.mss
self.cwnd_inc -= self.mss
self.plot_cwnd()
# self.trace("Window Size: %f" % (self.cwnd))
self.cancel_timer()
if not self.send_buffer.outstanding() == 0:
self.start_retransmit_timer(self.timeout)
self.send_window()
def retransmit(self, event):
""" Retransmit data. """
self.ss_thresh = max(self.cwnd / 2, self.mss)
self.ss_thresh -= self.ss_thresh % self.mss
self.slow_start = True
self.cwnd = float(self.mss)
self.trace("Entering Slow Start: SS Thresh = %s CWND = %s" %
(self.ss_thresh, self.cwnd))
self.plot_cwnd()
self.cwnd_inc = 0.0
if event:
self.trace("%s (%d) retransmission timer fired" %
(self.node.hostname, self.source_address))
self.timer = None
else:
self.trace("%s (%d) Fast retransmit occured" %
(self.node.hostname, self.source_address))
(data, sequence) = self.send_buffer.resend(size=self.mss, reset=True)
if len(data) == 0:
return
self.send_packet(data, sequence)
def start_retransmit_timer(self, time):
self.timer = Sim.scheduler.add(delay=time,
event='retransmit',
handler=self.retransmit)
def cancel_timer(self):
""" Cancel the timer. """
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self, packet):
""" Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK."""
# self.trace("%s (%d) received TCP segment from %d for %d" % (
# self.node.hostname, packet.destination_address, packet.source_address, packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
(buffer_data, sequence_number) = self.receive_buffer.get()
if len(buffer_data) > 0:
self.app.receive_data(buffer_data)
if sequence_number == packet.sequence:
self.ack = packet.sequence + len(buffer_data)
self.send_ack()
def send_ack(self):
""" Send an ack. """
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,
ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
''' A TCP connection between two hosts.'''
def __init__(self,
transport,
source_address,
source_port,
destination_address,
destination_port,
app=None,
window=1000):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
def trace(self, message):
''' Print debugging messages. '''
Sim.trace("TCP", message)
def receive_packet(self, packet):
''' Receive a packet from the network layer. '''
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self, data):
''' Send data on the connection. Called by the application. This
code currently sends all data immediately. '''
self.send_buffer.put(data)
print "Data added to buffer."
if self.send_buffer.available() > 0 and self.send_buffer.outstanding(
) < self.window:
new_data, new_sequence = self.send_buffer.get(self.mss)
# self.send_packet(new_data, new_sequence)
message = ("Window not full, sent packet: " + str(new_sequence))
print message
# self.send_packet(data,self.sequence)
# self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,
ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.timeout,
event='retransmit',
handler=self.retransmit)
def handle_ack(self, packet):
''' Handle an incoming ACK. '''
self.cancel_timer()
def retransmit(self, event):
''' Retransmit data. '''
self.trace("%s (%d) retransmission timer fired" %
(self.node.hostname, self.source_address))
def cancel_timer(self):
''' Cancel the timer. '''
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self, packet):
''' Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK.'''
self.trace("%s (%d) received TCP segment from %d for %d" %
(self.node.hostname, packet.destination_address,
packet.source_address, packet.sequence))
self.app.receive_data(packet.body)
self.send_ack()
def send_ack(self):
''' Send an ack. '''
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,
ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" %
(self.node.hostname, self.source_address,
self.destination_address, packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
""" A TCP connection between two hosts."""
def __init__(self, transport, source_address, source_port,
destination_address, destination_port, app=None, window=1000,drop=[],
fast_retransmit=False, measure=False):
Connection.__init__(self, transport, source_address, source_port,
destination_address, destination_port, app)
# -- Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# plot sequence numbers
self.plot_sequence_header()
# packets to drop
self.drop = drop
self.dropped = []
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# -- Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
self.fast_retransmit = fast_retransmit
self.last_ack = 0
self.last_ack_count = 0
self.measure = measure
self.total_queue_delay = 0
self.packet_count = 0
self.byte_count = 0
def trace(self, message):
""" Print debugging messages. """
Sim.trace("TCP", message)
def plot_sequence_header(self):
if self.node.hostname =='n1':
Sim.plot('sequence.csv','Time,Sequence Number,Event\n')
def plot_sequence(self,sequence,event):
if self.node.hostname =='n1':
Sim.plot('sequence.csv','%s,%s,%s\n' % (Sim.scheduler.current_time(),sequence,event))
def receive_packet(self, packet):
""" Receive a packet from the network layer. """
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self, data):
""" Send data on the connection. Called by the application."""
self.send_buffer.put(data)
self.send_window()
def send_window(self):
while self.send_buffer.outstanding() < self.window and self.send_buffer.available() > 0:
(packet_data, self.sequence) = self.send_buffer.get(self.mss)
self.send_packet(packet_data, self.sequence)
def send_packet(self, data, sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence, ack_number=self.ack)
if sequence in self.drop and not sequence in self.dropped:
self.dropped.append(sequence)
self.plot_sequence(sequence,'drop')
self.trace("%s (%d) dropping TCP segment to %d for %d" % (
self.node.hostname, self.source_address, self.destination_address, packet.sequence))
return
# send the packet
self.plot_sequence(sequence,'send')
self.trace("%s (%d) sending TCP segment to %d for %d" % (
self.node.hostname, self.source_address, self.destination_address, packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.start_retransmit_timer(self.timeout)
def handle_ack(self, packet):
""" Handle an incoming ACK. """
self.plot_sequence(packet.ack_number - 1000,'ack')
self.send_buffer.slide(packet.ack_number)
self.trace("%s (%d) received ACK from %d for %d" % (
self.node.hostname, packet.destination_address, packet.source_address, packet.ack_number))
if self.fast_retransmit:
if self.last_ack == packet.ack_number:
self.last_ack_count += 1
if self.last_ack_count == 4:
self.retransmit(None)
elif packet.ack_number > self.last_ack:
self.last_ack = packet.ack_number
self.last_ack_count = 1
self.cancel_timer()
if not self.send_buffer.outstanding() == 0:
self.start_retransmit_timer(self.timeout)
self.send_window()
def retransmit(self, event):
""" Retransmit data. """
if event:
self.trace("%s (%d) retransmission timer fired" % (self.node.hostname, self.source_address))
self.timer = None
else:
self.trace("%s (%d) Fast retransmit occured" % (self.node.hostname, self.source_address))
(data, sequence) = self.send_buffer.resend(self.mss)
if len(data) == 0:
return
self.send_packet(data, sequence)
def start_retransmit_timer(self, time):
self.timer = Sim.scheduler.add(delay=time, event='retransmit', handler=self.retransmit)
def cancel_timer(self):
""" Cancel the timer. """
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self, packet):
""" Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK."""
self.trace("%s (%d) received TCP segment from %d for %d" % (
self.node.hostname, packet.destination_address, packet.source_address, packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
(buffer_data, sequence_number) = self.receive_buffer.get()
if len(buffer_data) > 0:
self.app.receive_data(buffer_data)
if sequence_number == packet.sequence:
self.ack = packet.sequence + len(buffer_data)
if self.measure:
self.total_queue_delay += packet.queueing_delay
self.packet_count += 1
self.byte_count += packet.length
f = open(name="results.txt", mode="w")
f.write(str(self.total_queue_delay / self.packet_count) + "," + str(self.byte_count / Sim.scheduler.current_time()))
f.close()
self.send_ack()
def send_ack(self):
""" Send an ack. """
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence, ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" % (
self.node.hostname, self.source_address, self.destination_address, packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
''' A TCP connection between two hosts.'''
def __init__(self,transport,source_address,source_port,
destination_address,destination_port,app=None,window=1000):
Connection.__init__(self,transport,source_address,source_port,
destination_address,destination_port,app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
def trace(self,message):
''' Print debugging messages. '''
Sim.trace("TCP",message)
def receive_packet(self,packet):
''' Receive a packet from the network layer. '''
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self,data):
''' Send data on the connection. Called by the application. This
code currently sends all data immediately. '''
self.send_buffer.put(data)
print "Data added to buffer."
if self.send_buffer.available() > 0 and self.send_buffer.outstanding() < self.window:
new_data, new_sequence = self.send_buffer.get(self.mss)
# self.send_packet(new_data, new_sequence)
message = ("Window not full, sent packet: " + str(new_sequence))
print message
# self.send_packet(data,self.sequence)
# self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def send_packet(self,data,sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def handle_ack(self,packet):
''' Handle an incoming ACK. '''
self.cancel_timer()
def retransmit(self,event):
''' Retransmit data. '''
self.trace("%s (%d) retransmission timer fired" % (self.node.hostname,self.source_address))
def cancel_timer(self):
''' Cancel the timer. '''
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self,packet):
''' Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK.'''
self.trace("%s (%d) received TCP segment from %d for %d" % (self.node.hostname,packet.destination_address,packet.source_address,packet.sequence))
self.app.receive_data(packet.body)
self.send_ack()
def send_ack(self):
''' Send an ack. '''
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,ack_number=self.ack)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.ack_number))
self.transport.send_packet(packet)
class TCP(Connection):
''' A TCP connection between two hosts.'''
def __init__(self,transport,source_address,source_port,
destination_address,destination_port,app=None,window=1000):
Connection.__init__(self,transport,source_address,source_port,
destination_address,destination_port,app)
### Sender functionality
# send window; represents the total number of bytes that may
# be outstanding at one time
self.window = window
# send buffer
self.send_buffer = SendBuffer()
# maximum segment size, in bytes
self.mss = 1000
# largest sequence number that has been ACKed so far; represents
# the next sequence number the client expects to receive
self.sequence = 0
# retransmission timer
self.timer = None
# timeout duration in seconds
self.timeout = 1
# Round trip time in seconds
self.estimated_rtt = None
# Deviation of sample rtt from estimated rtt
self.deviation_rtt = None
### Receiver functionality
# receive buffer
self.receive_buffer = ReceiveBuffer()
# ack number to send; represents the largest in-order sequence
# number not yet received
self.ack = 0
# a list of all the queuing delays from the sender to receiver
self.queueing_delay_list = []
def trace(self,message):
''' Print debugging messages. '''
Sim.trace("TCP",message)
def receive_packet(self,packet):
''' Receive a packet from the network layer. '''
if packet.ack_number > 0:
# handle ACK
self.handle_ack(packet)
if packet.length > 0:
# handle data
self.handle_data(packet)
''' Sender '''
def send(self,data):
''' Send data on the connection. Called by the application. This
code uses the SendBuffer to send incrementally '''
self.send_buffer.put(data)
self.queue_packets()
def queue_packets(self):
''' Send the next set of packets if there's any to send. Limit based
on window size and the number of outstanding packets '''
while True:
if self.send_buffer.available() <= 0:
break
if self.send_buffer.outstanding() + self.mss > self.window:
break
packet_data = self.send_buffer.get(self.mss)
self.send_packet(packet_data[0], packet_data[1])
def send_packet(self,data,sequence):
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
body=data,
sequence=sequence,ack_number=self.ack,
sent_time=Sim.scheduler.current_time())
# send the packet
self.trace("%s (%d) sending TCP segment to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.sequence))
self.transport.send_packet(packet)
# set a timer
if not self.timer:
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def handle_ack(self,packet):
''' Handle an incoming ACK. '''
# Calculate Sample RTT
sample_rtt = Sim.scheduler.current_time() - packet.sent_time
self.trace("sample round trip time %f" % sample_rtt)
# Calculate the new estimated RTT
alpha = 0.125
if not self.estimated_rtt:
self.estimated_rtt = sample_rtt
else:
self.estimated_rtt = (1 - alpha) * self.estimated_rtt + alpha * sample_rtt
# Calculate the deviation of the sample RTT
beta = 0.25
if not self.deviation_rtt:
self.deviation_rtt = self.estimated_rtt/2
else:
self.deviation_rtt = (1 - beta) * self.deviation_rtt + beta * abs(sample_rtt - self.estimated_rtt)
# Calculate the Retransmission Timeout (RTO)
self.timeout = self.estimated_rtt + 4 * self.deviation_rtt
self.trace("changed the timeout to %f" % self.timeout)
self.sequence = packet.ack_number
self.send_buffer.slide(packet.ack_number)
self.cancel_timer()
if self.send_buffer.outstanding() or self.send_buffer.available():
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
self.queue_packets()
def retransmit(self,event):
''' Retransmit data. '''
self.trace("%s (%d) retransmission timer fired" % (self.node.hostname,self.source_address))
packet_data = self.send_buffer.resend(self.mss)
self.send_packet(packet_data[0], packet_data[1])
self.timeout = self.timeout * 2
self.trace("doubled the timeout to %f" % self.timeout)
self.timer = Sim.scheduler.add(delay=self.timeout, event='retransmit', handler=self.retransmit)
def cancel_timer(self):
''' Cancel the timer. '''
if not self.timer:
return
Sim.scheduler.cancel(self.timer)
self.timer = None
''' Receiver '''
def handle_data(self,packet):
''' Handle incoming data. This code currently gives all data to
the application, regardless of whether it is in order, and sends
an ACK.'''
self.queueing_delay_list.append(packet.queueing_delay)
self.trace("%s (%d) received TCP segment from %d for %d" % (self.node.hostname,packet.destination_address,packet.source_address,packet.sequence))
self.receive_buffer.put(packet.body, packet.sequence)
data = self.receive_buffer.get()
self.ack = len(data[0]) + data[1]
self.app.receive_data(data[0])
self.send_ack(packet.sent_time)
def send_ack(self, packet_sent_time=0):
''' Send an ack. '''
packet = TCPPacket(source_address=self.source_address,
source_port=self.source_port,
destination_address=self.destination_address,
destination_port=self.destination_port,
sequence=self.sequence,ack_number=self.ack,
sent_time=packet_sent_time)
# send the packet
self.trace("%s (%d) sending TCP ACK to %d for %d" % (self.node.hostname,self.source_address,self.destination_address,packet.ack_number))
self.transport.send_packet(packet)