eclipse-uprotocol · sophokles73 · Jan 12, 2026 · Jan 2, 2026 · Jan 12, 2026
diff --git a/basics/README.adoc b/basics/README.adoc
@@ -25,7 +25,7 @@ The following are the foundational requirements for uProtocol specifications:
 * *xref:uri.adoc[Addressing (UUri)]*
 * *xref:error_model.adoc[Error Model (UStatus, UCode)]*
 * *xref:uuid.adoc[Unique Universal Identifier (UUID)]*
-* *xref:qos.adoc[Quality of Service & Priority (UPriority)]*
+* *xref:upriority.adoc[Message Priority (UPriority)]*
 * *xref:uattributes.adoc[uProtocol Attributes (UAttributes)]*
 * *xref:umessage.adoc[uProtocol Message (UMessage)]*
 * *xref:permissions.adoc[Permissions]*
diff --git a/basics/uattributes.adoc b/basics/uattributes.adoc
@@ -139,13 +139,13 @@ Every message *MUST* have a unique message identifier. The timestamp contained i
 --
 
 |`priority`
-|xref:qos.adoc[UPriority]
+|xref:upriority.adoc[UPriority]
 |no
 a|
-The QoS level that this message should be processed/delivered with.
+The level of priority that this message should be processed/delivered with.
 [.specitem,oft-sid="dsn~up-attributes-priority~1",oft-needs="impl,utest",oft-tags="TransportLayerImpl"]
 --
-A consumer *MUST* assume a message to have the xref:qos.adoc#default-priority[default priority] if not set explicitly.
+A consumer *MUST* assume a message to have the xref:upriority.adoc#default-priority[default priority] if not set explicitly.
 --
 
 |`ttl`
@@ -225,12 +225,6 @@ a|A xref:../up-l2/dispatchers/README.adoc#dispatcher-types[uStreamer] can set th
 * *MUST* contain a non-empty _authority_name_ and
 * *MUST* contain wildcard values for all of the UUri's other fields.
 --
-
-|`priority`
-|xref:qos.adoc[UPriority]
-|yes
-a|
-The QoS level that this message should be processed/delivered with.
 |===
 
 [#notification-attributes]
@@ -312,9 +306,9 @@ a|A xref:uri.adoc[UUri] identifying the service provider's method to invoke.
 --
 
 |`priority`
-|xref:qos.adoc[UPriority]
+|xref:upriority.adoc[UPriority]
 |yes
-a|The xref:qos.adoc[QoS] level that this message should be processed/delivered with.
+a|The xref:upriority.adoc[level of priority] that this message should be processed/delivered with.
 
 [.specitem,oft-sid="dsn~up-attributes-request-priority~1",oft-needs="impl,utest",oft-tags="LanguageLibrary"]
 --
@@ -403,10 +397,10 @@ a|
 --
 
 |`priority`
-|xref:qos.adoc[UPriority]
+|xref:upriority.adoc[UPriority]
 |yes
 a|
-The xref:qos.adoc[QoS] level that this message should be processed/delivered with. 
+The xref:upriority.adoc[level of priority] that this message should be processed/delivered with. 
 
 [.specitem,oft-sid="dsn~up-attributes-response-priority~1",oft-needs="impl,utest",oft-tags="ServiceProvider"]
 --

diff --git a/basics/qos.adoc → basics/upriority.adoc b/basics/qos.adoc → basics/upriority.adoc
@@ -1,4 +1,4 @@
-= QoS
+= Message Priority (UPriority)
 :sectnums:
 
 The key words "*MUST*", "*MUST NOT*", "*REQUIRED*", "*SHALL*", "*SHALL NOT*", "*SHOULD*", "*SHOULD NOT*", "*RECOMMENDED*", "*MAY*", and "*OPTIONAL*" in this document are to be interpreted as described in https://www.rfc-editor.org/info/bcp14[IETF BCP14 (RFC2119 & RFC8174)]
@@ -21,21 +21,45 @@ SPDX-License-Identifier: Apache-2.0
 
 uProtocol allows messages to be exchanged between uEntities on the same and/or different devices. The network bandwidth and/or CPU cycles available for performing this task may be limited, though. uProtocol therefore supports priority based message processing at the xref:../up-l1/README.adoc[Transport] and xref:../up-l2/README.adoc[Communication Layer] based on https://datatracker.ietf.org/doc/html/rfc4594[RFC4594 - Configuration Guidelines for DiffServ Service Classes].
 
-For this purpose, each xref:umessage.adoc[UMessage] is assigned to one of the following service classes:
+For this purpose, each xref:umessage.adoc[UMessage] is assigned exactly one of the following classes:
 
-.QoS Classifications
+.Message Priority Classes
 [cols="1,4,3"]
 |===
 |Class |Description |Typical Use Case
 
-|*CS0* |Low Priority. No bandwidth assurance |File Transfer
-|*CS1* |Standard, undifferentiated application |General (unclassified)
-|*CS2* |Operations, Administration, and Management |Streamer messages (sub, connect, etc…)
-|*CS3* |Multimedia streaming |Video Streaming
-|*CS4* |Real-time interactive |High priority (RPC events)
-|*CS5* |Important |Signaling
-|*CS6* |Safety Critical |Network control
+|*CS0*
+|Low Priority. No bandwidth assurance
+|Bulk data transfer
+
+|*CS1*
+|Default priority
+|Generic, non-specific application level events
+
+|*CS2*
+|Operations, Administration, and Management
+|uSubscription messages (subscribe, etc.)
+
+|*CS3*
+|Multimedia streaming
+|Audio/Video frames
+
+|*CS4*
+|Real-time interactive
+|High priority (RPC messages)
+
+|*CS5*
+|Important
+|Signaling
+
+|*CS6*
+|Safety Critical
+|Network control
 |===
 
 [#default-priority]
-A UMessage *MAY* be assigned _explicitly_ to a service class by setting the message's xref:uattributes.adoc#common-attributes[`priority`] property to the desired value. If the property is not set, the UMessage belongs to class `CS1` by default.
+A UMessage *MAY* have a priority class assigned _explicitly_ by setting the message's xref:uattributes.adoc#common-attributes[_priority_] property to the desired value. If the property is not set, the UMessage belongs to class `CS1` by default.
+
+NOTE: The actual handling of message priority is implementation specific and may depend on the capabilities of the underlying transport protocol. Some transports may not support priority handling at all.
+
+NOTE: The example use cases provided above are intended as guidelines only. uEntities may choose to deviate from these guidelines based on specific application requirements.
diff --git a/up-core-api/uprotocol/v1/uattributes.proto b/up-core-api/uprotocol/v1/uattributes.proto
@@ -99,8 +99,7 @@ enum UMessageType {
 }
 
 
-// uProtocol Priority as defined in
-// https://github.com/eclipse-uprotocol/up-spec/blob/main/basics/qos.adoc[uProtocol Prioritization]
+// Message priority levels.
 enum UPriority {
     // Unspecified priority
     UPRIORITY_UNSPECIFIED = 0;

diff --git a/up-l1/README.adoc b/up-l1/README.adoc
@@ -160,9 +160,9 @@ NOTE: Certain uEntities like the xref:../up-l2/dispatchers/README.adoc[uStreamer
 
 [.specitem,oft-sid="req~utransport-send-qos-mapping~1",oft-needs="dsn,uman",oft-tags="TransportLayerImpl"]
 --
-* *MUST* document if and how the implementation maps the xref:../basics/qos.adoc[UMessage Service Classes] to an existing corresponding mechanism for message prioritization of the underlying transport protocol.
+* *MUST* document if and how the implementation maps the xref:../basics/upriority.adoc[UMessage Priority Classes] to an existing corresponding mechanism for message prioritization of the underlying transport protocol.
 +
-NOTE: An implementation *MAY* also completely ignore the service class and handle all messages equally, regardless of service class.
+NOTE: An implementation *MAY* also handle all messages equally, regardless of priority class.
 --
 
 [mermaid]

diff --git a/up-l1/cloudevents.adoc b/up-l1/cloudevents.adoc
@@ -110,7 +110,7 @@ a|The destination (address) of the message
 |`priority`
 |`priority`
 |String
-a| The message's priority as defined by xref:../basics/qos.adoc[QoS].
+a| The message's priority as defined by xref:../basics/upriority.adoc[Message Priority].
 
 * *MUST* be set to the value of the `uprotocol.ce_name` option defined for the
 link:../up-core-api/uprotocol/uattributes.proto[UPriority enum].

diff --git a/up-l1/mqtt_5.adoc b/up-l1/mqtt_5.adoc
@@ -82,7 +82,7 @@ a| The destination (address) of the message
 
 | _priority_
 | User Property [key: _5_]
-a| The message's service class as defined in xref:../basics/qos.adoc[QoS Doc]
+a| The message's priority class as defined in xref:../basics/upriority.adoc[Message Priority]
 
 * *MUST* be set to the value of the _uprotocol.ce_name_ option defined for the
 link:../up-core-api/uprotocol/uattributes.proto[UPriority enum].

diff --git a/up-l1/someip.adoc b/up-l1/someip.adoc
@@ -115,8 +115,8 @@ The following sections highlight the mapping of xref:../basics/uattributes.adoc[
 
 | priority | Not available in SOME/IP. Default UPriority values are used per UMessage type as described in xref:../basics/uattributes.adoc[UAttributes].
 
-* SOME/IP `NOTIFICATION` *SHOULD* use the xref:../basics/qos.adoc[CS1] priority.
-* SOME/IP `REQUEST` *SHOULD* use xref:../basics/qos.adoc[CS4] or higher priority.
+* SOME/IP `NOTIFICATION` *SHOULD* use the xref:../basics/upriority.adoc[CS1] priority.
+* SOME/IP `REQUEST` *SHOULD* use xref:../basics/upriority.adoc[CS4] or higher priority.
 * SOME/IP `RESPONSE` *MUST* use the priority from its corresponding `REQUEST` message.
 
 | ttl | Should be checked for incoming `UMESSAGE_TYPE_REQUEST` messages.

diff --git a/up-l2/dispatchers/README.adoc b/up-l2/dispatchers/README.adoc
@@ -62,7 +62,7 @@ NOTE: These communication layer requirements are still for point-2-point uEntity
 
 * *MAY* support additional UMessage delivery policies in general or per topic in the future
 * *SHOULD* maintain the (relative) order that messages have been received in, when dispatching messages to receivers
-* *SHOULD* consider a received UMessage's xref:../../basics/qos.adoc[service class] in their message dispatching strategy
+* *SHOULD* consider a received UMessage's xref:../../basics/upriority.adoc[priority class] in their message dispatching strategy
 * *MAY* batch UMessages when delivering to the Receiver
 * UMessages that cannot be delivered *MUST* be sent to the Dead Letter topic (DLT)
   ** DLT *MUST* include at least the UMessage header, SHOULD contain the full UMessage