When TL packet drop is turned on, and input bitrate exceeds the maxbw limitation, the MAXBW limit is suppressed. This can happen also when the amount of retransmission is high (see #638).
By default maxbw is limited to 1 Gbps (30 Mbps prior to v1.3.3).
Latest on the moment of testing SRT version 6f6b76b.
URI query both for receiver and sender:transtype=live&messageapi=1&payloadsize=1456&rcvbuf=125000000&sndbuf=125000000
Link RTT is 0.24 ms (local 1 Gbps switch).
Sender sends packets at 900 Mbps. Nothing stops it. But looks like the receiver is ackowleding packets at slower rate, thus the sender's buffer gets full.
E.g. this query actually limits sending rate to 30 Mbps:transtype=file&congestion=live&messageapi=1&payloadsize=1456&rcvbuf=125000000&sndbuf=125000000
The difference is that TL packet drop is turned off by transtype=file (there is no URI query socket option to turn off TSBPD directly).
Sender side packets. Notice the packets start dropping only at the end. And the sender starts printing error messages: SND-DROPPED 893 packets - lost delaying for 1032ms.
And the packets start dropping when the available sender's buffer size goes down to 0:
While the time interval between the packets is 400 μs, that corresponds to 30 Mbps.
The receiver's buffer size, although set to 1 GB, is actually limited by FC size, so it is actually only 300 Mbits (refer to #700).
In the end receiver closes the connection due to:SRT:RcvQ:worker*E:SRT.c: %915948307:SEQUENCE DISCREPANCY, reception no longer possible. REQUESTING TO CLOSE.
Setting maxbw=125000000 solves the problem, although in the described set up the size of the recevier's buffer is too small, and it anyway closes the connection with error message:
SRT:RcvQ:worker*E:SRT.c: %488590918:No room to store incoming packet: offset=0 avail=0 ack.seq=2032363150 pkt.seq=2032363150 rcv-remain=25599
SRT:RcvQ:worker*E:SRT.c: %488590918:No room to store incoming packet: offset=1 avail=0 ack.seq=2032363150 pkt.seq=2032363151 rcv-remain=25599
But notice the receiving rate is 900 Mbps:
While for the case when maxbw=30 Mbps the receiving rate is actually lower:
Also refer to #553, where almost similar experiment was conducted.
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