The subscriber sends a SUBSCRIBE_NAMESPACE control message on a new
bidirectional stream to a publisher to request the current set of matching
published namespaces and/or Established subscriptions, as well as future
updates to the set.
SUBSCRIBE_NAMESPACE Message {
Type (i) = 0x11,
Length (16),
Request ID (i),
Track Namespace Prefix (..),
Subscribe Options (i),
Number of Parameters (i),
Parameters (..) ...
}
-
Request ID: See Section 9.1.
-
Track Namespace Prefix: A Track Namespace structure as described in Section 2.4.1 with between 0 and 32 Track Namespace Fields. This prefix is matched against track namespaces known to the publisher. For example, if the publisher is a relay that has received PUBLISH_NAMESPACE messages for namespaces ("example.com", "meeting=123", "participant=100") and ("example.com", "meeting=123", "participant=200"), a SUBSCRIBE_NAMESPACE for ("example.com", "meeting=123") would match both. If an endpoint receives a Track Namespace Prefix consisting of greater than than 32 Track Namespace Fields, it MUST close the session with a
PROTOCOL_VIOLATION. -
Subscribe Options: Allows subscribers to request PUBLISH (0x00), NAMESPACE (0x01), or both (0x02) for a given SUBSCRIBE_NAMESPACE request.
-
Parameters: The parameters are defined in Section 9.2.2.
The publisher will respond with REQUEST_OK or REQUEST_ERROR on the response half
of the stream. If the SUBSCRIBE_NAMESPACE is successful, the publisher will
send matching NAMESPACE messages on the response stream if they are requested.
If it is an error, the stream will be immediately closed via FIN.
Also, any matching PUBLISH messages without an Established Subscription will be
sent on the control stream. When there are changes to the namespaces or
subscriptions being published and the subscriber is subscribed to them,
the publisher sends the corresponding NAMESPACE, NAMESPACE_DONE,
or PUBLISH messages.
A subscriber cannot make overlapping namespace subscriptions on a single
session. Within a session, if a publisher receives a SUBSCRIBE_NAMESPACE with a
Track Namespace Prefix that shares a common prefix with an established namespace
subscription, it MUST respond with REQUEST_ERROR with error code
PREFIX_OVERLAP.
The publisher MUST ensure the subscriber is authorized to perform this namespace subscription.
SUBSCRIBE_NAMESPACE is not required for a publisher to send PUBLISH_NAMESPACE, PUBLISH_NAMESPACE_DONE or PUBLISH messages to a subscriber. It is useful in applications or relays where subscribers are only interested in or authorized to access a subset of available namespaces and tracks.
If the FORWARD parameter (Section 9.2.2.8) is present in this message and equal to 0, PUBLISH messages resulting from this SUBSCRIBE_NAMESPACE will set the FORWARD parameter to 0. If the FORWARD parameter is equal to 1 or omitted from this message, PUBLISH messages resulting from this SUBSCRIBE_NAMESPACE will set the FORWARD parameter to 1, or indicate that value by omitting the parameter (see Section 5.1).
The publisher MUST NOT send NAMESPACE_DONE for a namespace suffix before the corresponding NAMESPACE. If a subscriber receives a NAMESPACE_DONE before the corresponding NAMESPACE, it MUST close the session with a 'PROTOCOL_VIOLATION'.