How to turn off NAK?

[toilandmoil]

I use srt_setsockopt function sets SRTO_NAKREPORT option to false at the sender and receiver

Through Wireshark packet capture, it is found that the receiver will still send NAK packets to indicate the loss of packets.

[ethouris]

"NAKREPORT" name is kinda misleading. This concerns only the "periodic NAK reports", that is, repeated LOSSREPORT in case when in a given expected time after previous LOSSREPORT the retransmission didn't happen.

For turning off LOSSREPORT sending completely, even this first time reported on loss detection, there's no option and this cannot be turned off. That is, it may be turned off if you turn on the packet filter and use FEC, in this case you have an option to either use ARQ (that is, reporting losses by LOSSREPORT) or not.

[maxsharabayko]

Further reading on types of NAK reports (loss-triggered and periodic) in SRT:
SRT RFC Section 4.8.2. Packet Retransmission (NAKs)

[toilandmoil]

"NAKREPORT" name is kinda misleading. This concerns only the "periodic NAK reports", that is, repeated LOSSREPORT in case when in a given expected time after previous LOSSREPORT the retransmission didn't happen.

For turning off LOSSREPORT sending completely, even this first time reported on loss detection, there's no option and this cannot be turned off. That is, it may be turned off if you turn on the packet filter and use FEC, in this case you have an option to either use ARQ (that is, reporting losses by LOSSREPORT) or not.

Think you very much. Indeed, the NAK message can be closed by setting FEC.

[maxsharabayko]

One more way to indirectly disable retransmissions is to set msgttl to some low value (e.g. RTT/2 or 1ms).
In this case, the receiver will send a loss report, but the sender will not retransmit a packet, but send a drop request instead.

See msgttl in SRT_MSGCTRL.
Message Drop Request control packet (SRT RFC).

[yankee624]

@maxsharabayko Hi, I ran into a similar question.
Do you mean that I should add an SRT_MSGCTRL argument (with small msgttl value) to every srt_sendmsg2 call?

Also, is there any update in how to disable retransmission?

Thanks in advance!

[maxsharabayko]

@yankee624
With PR #2714 you could set SRTO_MAXREXMITBW to 0 to completely disable retransmissions.

[jeandube]

@yankee624 With PR #2714 you could set SRTO_MAXREXMITBW to 0 to completely disable retransmissions.

@maxsharabayko Does this mean that SRTO_MAXREXMITBW is not a sender-only option?

[maxsharabayko]

Sorry, you are right. That would be on the sender side.