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SCTP Parameters

Dictionaries

Dictionaries

SctpParameters

Parameters of the SCTP association.

Field	Type	Description	Required
`port`	Number	Must always equal 5000.	Yes
`OS`	Number	Initially requested number of outgoing SCTP streams.	Yes
`MIS`	Number	Maximum number of incoming SCTP streams.	Yes
`maxMessageSize`	Number	Maximum allowed size for SCTP messages.	Yes

NumSctpStreams

Field	Type	Description	Required	Default
`OS`	Number	Initially requested number of outgoing SCTP streams (from 1 to 65535).	No	1024
`MIS`	Number	Maximum number of incoming SCTP streams (from 1 to 65535).	No	1024

Both OS and MIS are part of the SCTP INIT+ACK handshake. OS refers to the initial number of outgoing SCTP streams that the server side transport creates (to be used by DataConsumers), while MIS refers to the maximum number of incoming SCTP streams that the server side transport can receive (to be used by DataProducers). So, if the server side transport will just be used to create data producers (but no data consumers), OS can be low (~1).

When obtaining numSctpStreams from mediasoup-client via device.sctpCapabilities.numStreams, the obtained fields must be reversed:

const transport = await router.createWebRtcTransport(
  {
    enableSctp     : true,
    numSctpStreams :
    {
      OS  : clientSctpCapabilities.numStreams.MIS,
      MIS  : clientSctpCapabilities.numStreams.OS
    }
  });

SctpStreamParameters

SCTP stream parameters describe the reliability of a certain SCTP stream.

Field	Type	Description	Required	Default
`streamId`	Number	SCTP stream id	true
`ordered`	Boolean	Whether data messages must be received in order. if true the messages will be sent reliably.	No	true
`maxPacketLifeTime`	Number	When `ordered` is false indicates the time (in milliseconds) after which a SCTP packet will stop being retransmitted.	No
`maxRetransmits`	Number	When `ordered` is false indicates the maximum number of times a packet will be retransmitted.	No

If ordered is true then maxPacketLifeTime and maxRetransmits must be false.
If ordered if false, only one of maxPacketLifeTime or maxRetransmits can be true.