Dear authors of schc-over-lorawan,

Thank you for this work.
Following is my review handled as part of IoT-DIR review process:

Section 4:
[RJ] The architecture shows "Join Server" but the section has no explanation for it.

Section 4:
"The Network Gateway (NGW) is the interconnection node between the Radio Gateway and the Internet."
[RJ] It is mentioned that NGW is the gateway to the Internet but the SCHC C/D and F/R is handled on the LoRaWAN application server. How would the compressed packets be sent out to the Internet from NGW?
[RJ] In the last para of the section it is mentioned that "(SCHC gateway) acts as the first-hop IP router for the device. This means that the NGW is not the interconnection node between the RGW and the Internet.

Section 4:
[RJ] The terms used in the architecture figure 3 and the document are different/confusing.
For e.g., the figure mentions Application Server which is referred to as SCHC Gateway in the overall document. The figure mentions Network Server but is referred to as Network Gateway (NGW) in the overall document. As a reader, I wanted to use this architecture diagram as a ref but the terms mentioned in the diagram are different from those used in the draft elsewhere.

Section 4.1:
"The lower the downlink latency, the higher the power consumption."
[RJ] I didn't understand why lower latency could result in higher power consumption. I think the intention was to use either downlink frequency or listen periodicity as a driver for higher power consumption.

Section 4.3/4.4:
[RJ] The terms "frames" and "messages" are used interchangeably. Would be better to use a fixed term, or else clarify these terms in the document.

Section 4.6:
[RJ] FRMPayload is not defined anywhere.

Section 5.1:
[RJ] I believe the term "fragmented datagram" should be used in place of "fragmentation datagram" in the whole of this para.

Section 5.1:
"It uses another FPort for data downlink and its associated SCHC control uplinks, named FPortDown in this document."
[RJ] Just for my understanding, the FPortUp and FPortDown are disjoint sets i.e., an FPort part of FPortUp set cannot be part of the FPortDown set. Is this correct? If yes, can we make it explicit in the document?

Section 5.2:
"RuleID = 22 (8-bit) for which SCHC compression was not possible..."
[RJ] I believe RuleID = 22 is provisioned for LoRaWAN messages which are sent uncompressed i.e., if a device wants to send an uncompressed IPv6 then it can use this RuleID. Is this correct? If yes, can we state this sample use-case for RuleID=22?

Section 5.3:
"There is a small probability of IID collision in a LoRaWAN network, if such event occurs the IID can be changed by rekeying the device on L2 level (ie: trigger a LoRaWAN join)."
[RJ] As I understand, IID collision can be detected only by the Network Gateway. How would the Network Gateway initiate a LoRaWAN join? Section 4.4 defines that only the end device can initiate a JoinRequest frame.

Section 5.6.1:
Please provide a reference to Section 8.2.4 in RFC 8724 for DTag.

Section 5.6.2:
The term Tile is not defined in the document nor is there a ref to RFC 8724. Better to redefine it here or at least have a ref to RFC 8724.

Section 5.6.3:
The term "applicative uplink" is used in this and subsequent sections. Are you referring to the application uplink? Not sure of what applicative means in the context?

Section 5.6.3.5.1:
"LoRaWAN layer will respect the regulation if required."
I believe the local spectrum regulation is what is referred here, but am not sure.

Section 6: Security Considerations
The section mentions the use of IID for privacy protection and the use of AES-128 encryption for payload encryption. However, it is not clear to me as to how the replay protection can be handled i.e. if an attacker replays the data sent by any other node previously, how can it be protected? I believe this is handled as part of the LoRaWAN mac layer?

Minor Nits:

Section 3:

Known information are part of the "context".
Known information is of the "context".

This component called SCHC...
This component is called SCHC...

...the RG is called a Gateway...
...the RGW is called a Gateway...

Section 4:

SCHC C/D and F/R are LoRaWAN Application Server;
SCHC C/D and F/R are handled by LoRaWAN Application Server;

Section 4.4:
...contains (amongst other fields) the major network's settings...
...contains (amongst other fields) the network's major settings...

Section 4.7:
...a packet send over LoRaWAN radio link...
...a packet sent over LoRaWAN radio link...

Section 5.2:
In order to improve interoperability RECOMMENDED fragmentation....
In order to improve interoperability, RECOMMENDED fragmentation....

Section 5.6.2:
In that case the device is the fragmentation transmitter, and the SCHC gateway the fragmentation receiver.
In that case, the device is the fragment transmitter, and the SCHC gateway is the fragment receiver.

Section 5.6.3.1: Figure title
"including LoraWAN FPort"
"including LoRaWAN FPort"

Section 6: Section Title
Security considerations
Security Considerations