[tcpdump-workers] Public Release of Z-Wave G.9959 TAP Specification

2022-12-05 Thread Chris Brandson via tcpdump-workers
--- Begin Message ---
Hello everyone,

We are pleased to publish the draft Z-Wave G.9959 TAP Specification at:

https://gitlab.com/exegin/zwave-g9959-tap 


This provides a definition of a proposed Data Link Type (DLT) to encapsulate 
G.9959 frames captured by over-the-air packet capture hardware. This G.9959 TAP 
contains capture metadata both necessary correct interpretation of the frame 
format and capture metadata such as RSS (received signal strength) useful for 
network monitoring and maintenance. The frames encapsulated by the Z-Wave 
G.9959 TAP are specified in https://www.itu.int/rec/T-REC-G.9959 
. 

Following review, and if needed any updates, it is requested that a DLT value 
be assigned to this specification. Once assigned the document will be updated 
with the DLT value and published as version 1.0.

Comments and feedback are appreciated.

Regards,

+ Chris Brandson

Exegin Technologies
401 - 2071 Kingsway Avenue
Port Coquitlam BC V3C 6N2
Canada

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> On Nov 15, 2022, at 4:59 PM, Guy Harris via tcpdump-workers 
>  wrote:
> 
> 
> From: Guy Harris 
> Subject: Re: [tcpdump-workers] Resend: Request for new DLT Value
> Date: November 15, 2022 at 4:59:31 PM PST
> To: Chris Brandson 
> Cc: tcpdump-workers@lists.tcpdump.org
> 
> 
> On Nov 15, 2022, at 3:50 PM, Chris Brandson via tcpdump-workers 
>  wrote:
> 
>> The ITU Recommendation G.9959 document can be found here 
>> https://www.itu.int/rec/T-REC-G.9959 . 
>> Work is ongoing on a wireshark dissector (hence the request for DLT 
>> LINKTYPE) and the TAP encapulation is still in development and will be 
>> published shortly. 
> 
> Let us know when you have a draft ready for us to look at.
> 
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Re: [tcpdump-workers] Public Release of Z-Wave G.9959 TAP Specification

2022-12-05 Thread Denis Ovsienko via tcpdump-workers
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On Mon, 5 Dec 2022 11:53:11 -0800
Chris Brandson via tcpdump-workers 
wrote:

> Hello everyone,
> 
> We are pleased to publish the draft Z-Wave G.9959 TAP Specification
[...]

Hello Chris.

Thank you for preparing the document.  I am not familiar with the
standard to make more substantial comments, but a few things seem to
require some attention:

* Page 7: "Length is a minimum of 4 octets and must be a multiple of 4.
  The addition of new TLVs does not and must not require incrementing
  the version number." -- this definition automatically creates a
  problem space on the receiving/reading end of this encoding because
  slightly more than 75% of all possible length values are invalid by
  definition. The classic solution would be not to include the first 4
  octets into the length, and to count in multiples of 4, this way any
  length value would be valid, free of underflows and better consumable
  by simple parsers such as BPF bytecode.

* Page 8: "Z-Wave PHY Payload" -- is this the PPDU from Figure A.7 of
  G.9959 2015/01, starting from "preamble sequence"?

* Page 9: "length - number of octets for type in value field (not
  including padding)" -- this definition looks better, but in the next
  three TLV diagrams the length does include the T and the L.

* Page 10: If the list of region code points is a copy/subset of an
  external registry, it would help to give an exact reference.  Ditto
  bit rate code points.  Clearly there is some relation with tables A.1
  and A.2 from G.9959 2015/01.

-- 
Denis Ovsienko
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