Padding — MoQT draft-18 §11.5.

An endpoint MAY send padding on unidirectional streams or datagrams. Padding does not carry Objects or any other application data. An endpoint can use padding to probe for additional bandwidth while minimizing the impact on the delivery of application data.

To avoid interfering with the delivery of Objects, senders SHOULD send padding streams at a lower priority than any control stream or Object data.

11.5.1. Padding Streams

An endpoint MAY open a unidirectional stream with a stream type of 0x132B3E28 to send padding data. The stream begins with the stream type, followed by zero or more bytes that MUST all be set to zero.

PADDING STREAM {
  Type (vi64) = 0x132B3E28,
  Padding Data (..) = 0x00..
}

Figure 28: MOQT Padding Stream

The receiver MUST discard all data received on a padding stream to prevent exhausting flow control.

Either the sender or the receiver MAY cancel a padding stream at any time without affecting any MOQT application state.

11.5.2. Padding Datagrams

An endpoint MAY send a datagram with a type of 0x132B3E29 to send padding data. The datagram contains the type followed by zero or more bytes that MUST all be set to zero.

PADDING DATAGRAM {
  Type (vi64) = 0x132B3E29,
  Padding Data (..) = 0x00..
}

Figure 29: MOQT Padding Datagram

The receiver MUST discard all data received in a padding datagram.