upriority.adoc

Message Priority (UPriority)

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 IETF BCP14 (RFC2119 & RFC8174)

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1. Overview

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 Transport and Communication Layer based on RFC4594 - Configuration Guidelines for DiffServ Service Classes.

For this purpose, each UMessage is assigned to exactly one of the following classes:

Table 1. Message Priority Classes

Class	Description	Typical Use Case
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

A UMessage MAY be assigned explicitly to a service class by setting the message’s 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.