Modifying traffic identifier (TID) for video stream

[kuldeep-gill-skydio]

Does anyone know how I can modify the tid for udp packets sent using kinesis webrtc? Capturing the packets through wireshark, I see all the video packets go as besteffort and I would like to change it to video to reduce the contention time.

[MushMal]

If you are referring top DSCP/TOS on the packet? I don't think anything is being set and whether it actually will make any difference. However, you might want to try to set socket options here:

amazon-kinesis-video-streams-webrtc-sdk-c/src/source/Sctp/Sctp.c

Line 17 in ced19d0

STATUS configureSctpSocket(struct socket* socket)

and see whether it makes any difference in your ISP.

Would love to hear back

[kuldeep-gill-skydio]

Thanks! I will try and evaluate if it provides any latency benefit.

[kuldeep-gill-skydio]

@MushMal I tried adding the TOS here but the packets are still coming with best effort. Do I need to make changes elsewhere too?

@@ -22,6 +22,7 @@ STATUS configureSctpSocket(struct socket* socket)
     struct sctp_event event;
     UINT32 i;
     UINT32 valueOn = 1;
+    UINT32 tid_value = 0x80; // sending the data as video tid
     UINT16 event_types[] = {SCTP_ASSOC_CHANGE,   SCTP_PEER_ADDR_CHANGE,      SCTP_REMOTE_ERROR,
                             SCTP_SHUTDOWN_EVENT, SCTP_ADAPTATION_INDICATION, SCTP_PARTIAL_DELIVERY_EVENT};
 
@@ -36,6 +37,9 @@ STATUS configureSctpSocket(struct socket* socket)
     // delays are introduced, at the cost of more packets in the network.
     CHK(usrsctp_setsockopt(socket, IPPROTO_SCTP, SCTP_NODELAY, &valueOn, SIZEOF(valueOn)) == 0, STATUS_SCTP_SESSION_SETUP_FAILED);
 
+    // by default packets are sent as besteffort
+    // modifying the TOS to video to enhance performance in congested enviornment
+    CHK(usrsctp_setsockopt(socket, IPPROTO_IP, IP_TOS, &tid_value, SIZEOF(tid_value)) == 0, STATUS_SCTP_SESSION_SETUP_FAILED);   
     MEMSET(&event, 0, SIZEOF(event));
     event.se_assoc_id = SCTP_FUTURE_ASSOC;
     event.se_on = 1;

[kuldeep-gill-skydio]

This doesn't work either:

CHK(usrsctp_setsockopt(socket, IPPROTO_SCTP, IP_TOS, &tid_value, SIZEOF(tid_value)) == 0, STATUS_SCTP_SESSION_SETUP_FAILED); 

[MushMal]

Oops, I am terribly sorry. I pointed to the location for sending/receiving the data channel bits and not the rtp.

Here is where you can configure and check whether your network equipment actually honors the dscp/tos

amazon-kinesis-video-streams-webrtc-sdk-c/src/source/Ice/Network.c

Line 168 in 08e4d29

if (setsockopt(sockfd, SOL_SOCKET, NO_SIGNAL, &optionValue, SIZEOF(optionValue)) < 0) {

You can issue another setsockopt call with IPPROTO_IP/IP_TOS or a more platform independent way using SOL_SOCKET/SO_PRIORITY