def A_input(self, pkt):
# process the ACK, NACK from B
if pkt.checksum == pkt.get_checksum() and pkt.acknum == self.seq:
self.state = "WAIT_LAYER5"
self.seq = 0 if self.seq else 1
evl.remove_timer()
else:
to_layer_three("A", self.lastPkt)
def A_handle_timer(self):
# go back n, A_handle_timer
# Read all the sent packet that it is not acknowledged
# using "read_all()" of the circular buffer and resend them
# If you need to resend packets, set a timer after that
for ptk in self.window.read_all() :
if ptk.seqnum >= self.base :
to_layer_three("A", ptk)
evl.start_timer("A", self.estimated_rtt)
def A_output(self, m):
# go back n, A_output
# If the buffer is full, just drop the packet
# Construct the packet based on the message.
# Make sure that the sequence number is correct
# Send the packet and save it to the circular buffer using "push()" of circular_buffer
# Set the timer using "evl.start_timer(entity, time)", and the time should be set to estimated_rtt.
# iMake sure that there is only one timer started in the event list
# if not self.window.isfull() :
if self.nextSeq < self.base + self.windowSize :
pkt = packet(seqnum=self.nextSeq, payload=m)
# print(str(pkt.payload.data))
self.window.push(pkt)
to_layer_three("A", pkt)
# if self.base == self.nextSeq :
evl.start_timer("A", self.estimated_rtt)
self.nextSeq += 1
def send_ack(AorB, ack):
pkt = packet(acknum=ack)
pkt.checksum = pkt.get_checksum()
to_layer_three(AorB, pkt)
def A_output(self, m):
# TODO: called from layer 5, pass the data to the other side
pkt = packet(seqnum=self.seq, payload=m)
to_layer_three("A", pkt)
def A_handle_timer(self):
# resend the packet as needed
to_layer_three("A", self.lastPkt)
evl.start_timer("A", self.estimated_rtt)
def A_output(self, m):
pkt = packet(seqnum=self.seq, payload=m)
to_layer_three("A", pkt)
evl.start_timer("A", self.estimated_rtt)
self.state = "WAIT_ACK"
self.lastPkt = pkt
