1. required/REQUIRED

• 3.2.2.3.9 User Property "The receiver of a CONNACK containing this property is not required to parse or process this property." This sentence does not appear in the description of User Property in other packets, so I am not sure that it is needed here.
  If a sentence is needed, it would be clearer to say
  "The content and meaning of this property is not defined by this specification. The receiver of a CONNACK containing this property MAY ignore it".

• 4.10.1 change "However, this is not required." to "However, this is not necessary".

• 4.12. "the exchanges and processing required by the Client and Server to complete the authentication" -> "the exchanges and processing to be performed by the Client and Server to complete the authentication."

• 4.12 "This property can be used to provide data as required by the Authentication Method." -> "This property can be used to provide data needed by the Authentication Method."

• 4.12 "The Client and Server exchange AUTH packets as required until the Server accepts" delete "as required"

• 4.12.1 "to indicate that more authentication data is required." -> "to indicate that more authentication data is needed."

2. should/SHOULD

• 3.2.2.2 and 3.14.2.1 (tables) rcs 156/157 should ->SHOULD