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protocol adjustment

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if we are loosing a burst ACK because of fading signals or bad conditions or just because - combined with a changing speed level -  theres now a good chance we are not loosing the entire data frame because of a corrupted CRC, anymore. We are now searching in already received data, if our new (smaller) data chunk already exists. If so, we are stripping the entire data to this position and adding our new data chunk. If not, it seems we received new data the regulary way. However, this could cause problems if we have a too small data entropie. We might also check if we have an increased NACK counter or if a data chunk exists, twice or more -  in a further step
This commit is contained in:
dj2ls 2022-02-18 09:58:49 +01:00
parent 2836072dc5
commit 6e0796f5a0
1 changed files with 30 additions and 7 deletions
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37
tnc/data_handler.py
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@ -46,7 +46,7 @@ class DATA():
self.data_frame_bof = b'BOF' # 2 bytes for the BOF End of File indicator in a data frame
self.data_frame_eof = b'EOF' # 2 bytes for the EOF End of File indicator in a data frame
self.rx_n_max_retries_per_burst = 10
self.rx_n_max_retries_per_burst = 15
self.n_retries_per_burst = 0
self.received_low_bandwith_mode = False # indicator if we recevied a low bandwith mode channel ope ner
@ -78,7 +78,7 @@ class DATA():
self.rx_frame_bof_received = False
self.rx_frame_eof_received = False
self.transmission_timeout = 30 # transmission timeout in seconds
self.transmission_timeout = 60 # transmission timeout in seconds
worker_thread_transmit = threading.Thread(target=self.worker_transmit, name="worker thread transmit",daemon=True)
worker_thread_transmit.start()
@ -326,13 +326,36 @@ class DATA():
# if frame buffer ends not with the current frame, we are going to append new data
# if data already exists, we received the frame correctly, but the ACK frame didnt receive its destination (ISS)
if not static.RX_FRAME_BUFFER.endswith(temp_burst_buffer):
static.RX_FRAME_BUFFER += temp_burst_buffer
static.RX_BURST_BUFFER = []
else:
if static.RX_FRAME_BUFFER.endswith(temp_burst_buffer):
structlog.get_logger("structlog").info("[TNC] ARQ | RX | Frame already received - sending ACK again")
static.RX_BURST_BUFFER = []
# here we are going to search for our data in the last received bytes
# this increases chance we are not loosing the entire frame in case of signalling frame loss
else:
# static.RX_FRAME_BUFFER --> exisitng data
# temp_burst_buffer --> new data
# search_area --> area where we want to search
search_area = 510
search_position = len(static.RX_FRAME_BUFFER)-search_area
# fin dposition of data. returns -1 if nothing found in area else >= 0
get_position = static.RX_FRAME_BUFFER[search_position:].find(temp_burst_buffer)
# if we find data, replace it at this position with the new data and strip it
if get_position >= 0:
static.RX_FRAME_BUFFER = static.RX_FRAME_BUFFER[:search_position + get_position]
static.RX_FRAME_BUFFER += temp_burst_buffer
structlog.get_logger("structlog").warning("[TNC] ARQ | RX | replacing existing buffer data", area=search_area, pos=get_position)
# if we dont find data n this range, we really have new data and going to replace it
else:
static.RX_FRAME_BUFFER += temp_burst_buffer
structlog.get_logger("structlog").debug("[TNC] ARQ | RX | appending data to buffer")
# lets check if we didnt receive a BOF and EOF yet to avoid sending ack frames if we already received all data
if not self.rx_frame_bof_received and not self.rx_frame_eof_received and data_in.find(self.data_frame_eof) < 0: