SUBSCRIBES_BLOCKED — MoQT draft-09 §7.21.

The SUBSCRIBES_BLOCKED message is sent when a subscriber would like to begin a new subscription, but cannot because the Subscribe ID would exceed the Maximum Subscribe ID value sent by the peer. The subscriber SHOULD send only one SUBSCRIBES_BLOCKED for a given Maximum Subscribe ID.

A publisher MAY send a MAX_SUBSCRIBE_ID upon receipt of SUBSCRIBES_BLOCKED, but it MUST NOT rely on SUBSCRIBES_BLOCKED to trigger sending a MAX_SUBSCRIBE_ID, because sending SUBSCRIBES_BLOCKED is not required.

SUBSCRIBES_BLOCKED
{
  Type (i) = 0x1A,
  Length (i),
  Maximum Subscribe ID (i),
}

Figure 22: MOQT SUBSCRIBES_BLOCKED Message

Maximum Subscribe ID: The Maximum Subscribe ID for the session on which the subscriber is blocked. More on Subscribe ID in Section 7.4.