| Issuer Name |
- CN = The `model-name` from the `agent-info` message, as
- also set in the `agent-info` message.
+ | CN = The `model-name` from the [=agent-info=] message.
O = See note.
L = See note.
ST = See note.
@@ -428,6 +445,92 @@ Variable-length integers are encoded in the [=Variable-Length Integer Encoding=]
used by [[!RFC9000|QUIC]].
+Metadata Discovery {#metadata}
+----------------------------------
+
+To learn metadata about another agent, an agent may send an
+[=agent-info-request=] message and receive back an [=agent-info-response=]
+message. Any agent may send this request at any time after a QUIC connection
+is established.
+
+If an agent changes any information in its [=agent-info=] message, it should
+send an [=agent-info-event=] message to all other connected agents with the new
+[=agent-info=] (without waiting for an [=agent-info-request=]).
+
+The [=agent-info=] message contains the following fields:
+
+: display-name (required)
+:: The display name of the agent, intended to be displayed to a user by the
+ requester. The requester should indicate through the UI if the responder
+ is not authenticated or if the display name changes.
+
+: model-name (optional)
+:: If the agent is a hardware device, the model name of the device. This is
+ used mainly for debugging purposes, but may be displayed to the user of the
+ requesting agent.
+
+: capabilities (required)
+:: A list of capability IDs that the agent supports. Capability IDs are
+ unsigned integers. The meaning of specific capability IDs is defined by
+ application protocols that use this network protocol. See
+ [[#capabilities-registry]] for the extensibility mechanism.
+
+: state-token (required)
+:: A random alphanumeric value consisting of 8 characters in the range
+ [0-9A-Za-z]. This value is set before the agent makes its first connection
+ and must be set to a new value when the agent is reset or otherwise loses
+ all of its state related to this protocol.
+
+: locales (required)
+:: The agent's preferred locales for display of localized content, in the order
+ of user preference. Each entry is an RFC5646 [=language tag=].
+
+### Capabilities Registry ### {#capabilities-registry}
+
+Capability IDs allow agents to indicate which protocol features they support.
+The capabilities field in [=agent-info=] contains a list of capability IDs.
+
+Capability IDs 1-999 are reserved for the Open Screen Protocol. The
+[Open Screen Application Protocol](https://w3c.github.io/openscreenprotocol/application.html)
+defines capabilities in this range.
+
+Capability IDs 1000 and above are available for extensions. Extension authors
+should register their capability IDs in the public registry to prevent
+conflicts.
+
+See the [Capabilities
+Registry](https://github.com/w3c/openscreenprotocol/blob/main/capabilities.md)
+for a list of all known capabilities.
+
+Connection Keep-Alive {#keep-alive}
+----------------------------------
+
+If a listening agent wishes to receive messages from an advertising agent or an
+advertising agent wishes to send messages to a listening agent, it may wish to
+keep the QUIC connection alive by periodically sending data on the connection.
+
+To keep a QUIC connection alive, an agent may send an [=agent-status-request=]
+message, and any agent that receives an [=agent-status-request=] message should
+send an [=agent-status-response=] message. Such messages should be sent more frequently than the QUIC
+idle_timeout transport parameter (see [=Transport Parameter Encoding=] in QUIC)
+and QUIC PING frames should not be used. An idle_timeout transport parameter
+of 25 seconds is recommended. The agent should behave as though a timer less
+than the idle_timeout were reset every time a message is sent on a QUIC stream.
+If the timer expires, an [=agent-status-request=] message should be sent.
+
+Once neither side needs to keep the connection alive for the purposes of
+sending or receiving messages, the connection should be closed with an error
+code of 5139.
+
+If a listening agent wishes to send messages to an advertising agent, the
+listening agent can connect to the advertising agent "on demand"; it does not
+need to keep the connection alive.
+
+If an OSP agent suspends its network connectivity (e.g. for power saving
+reasons), it should attempt to resume QUIC connections to the OSP agents to
+which it was previously connected once network connectivity is restored.
+
+
Authentication {#authentication}
================================
@@ -772,12 +875,9 @@ requires users to make informed decisions about which agents to trust.
Because DNS-SD [=Instance Names=] are the primary information that the user
sees prior to authentication, careful presentation of these names is necessary.
-Issue(346): Rephrase to not link DNS-SD with an agent-info, an application
-message.
-
Agents must treat Instance Names as unverified information, and should check
that the Instance Name is a prefix of the display name received through the
-agent-info message after a successful QUIC connection. Once an
+[=agent-info=] message after a successful QUIC connection. Once an
agent has done this check, it can show the name as a verified
display name.
diff --git a/network_messages.cddl b/network_messages.cddl
index de83bc3..708c28e 100644
--- a/network_messages.cddl
+++ b/network_messages.cddl
@@ -1,3 +1,54 @@
+; Base types for request/response messages
+request = (
+ 0: request-id ; request-id
+)
+
+response = (
+ 0: request-id ; request-id
+)
+
+request-id = uint
+
+; type key 10
+agent-info-request = {
+ request
+}
+
+; type key 11
+agent-info-response = {
+ response
+ 1: agent-info ; agent-info
+}
+
+; type key 120
+agent-info-event = {
+ 0: agent-info ; agent-info
+}
+
+agent-info = {
+ 0: text ; display-name
+ ? 1: text ; model-name
+ 2: [* uint] ; capabilities
+ 3: text ; state-token
+ 4: [* text] ; locales
+}
+
+; type key 12
+agent-status-request = {
+ request
+ ? 1: status ; status
+}
+
+; type key 13
+agent-status-response = {
+ response
+ ? 1: status ; status
+}
+
+status = {
+ 0: text ; status
+}
+
; type key 1001
auth-capabilities = {
0: uint ; psk-ease-of-input
|