[Vm-dev] Re: SecureSession frame types

Robert Withers robert.w.withers at gmail.com
Sun Dec 20 14:20:28 UTC 2015


My apologies for #2 below; what I said is wrong. The smallest message 
will be 8 bytes, as the messageSpecification is not FEC encoded. I will 
repair the doc as there are some issues with the spec and layout...done. 
Once again the link is: 
https://www.dropbox.com/s/zj2i1votg432b2p/FrameTypes.pptx?dl=0

  * MessageSpecification is 8 bytes binary encoded.
  * Header is always asn.1 encoded
  * All messages may be FEC encoded with the FEC header asn.1 encoded.
  * Data Message payload is encrypted.



Change query:
Regarding the Message Specification, with a hdrSize...I don't think we 
need it. The message size includes everything + the 8 bytes spec. The 
hdrType will specify the kind of message and header. The specific header 
knows it's own size and layout.  Therefor, we have 16bits free if we 
keep an 8 byte msgSpec. Let's rework it to a 7 byte msgSpec as below.  
Perhaps it is useful to be 64bit aligned, so leave it at 8. Thoughts? 
Does this work?


*msgSpec: 7 bytes binary encoded*

  * HeaderSpecification: 3 bytes
      o multicastSymbol: 6 bits
      o sanguinity: 7 bits
      o msgVersion: 5 bits
      o hdrType: 6 bits
  * msgSize: 2nd word, 4 bytes
      o 4 bytes (total size with msgSpec, header, payload sizes)


regards,
robert


On 12/20/2015 07:01 AM, Robert Withers wrote:
> Good morning, just a few comments and questions..
>
>     1) current 4bits for msgVersion and 4bits for hdrType. With 14
>     messages and some not implemented (suspend/resume/...) we have
>     little headroom in 4bits of hdrType.  Shall I make the msgVersion
>     3bits and the hdrType 5bits?
>
>     2) the smallest interleaved FEC encoded msg is 30 bytes. With 8
>     bytes of data: a msgSpec, using RS(15,9) with 4bit symbols, and 4
>     symbol block interleaving, the smallest on the wire is 30 bytes.
>     Without FEC enabled is it 8 bytes.
>
>     3) when run to the end of hdrType room, we can add a jump tag and
>     have a second hdrType field as the 9th byte.
>
>
> Again, the valid document  link is: 
> https://www.dropbox.com/s/zj2i1votg432b2p/FrameTypes.pptx?dl=0
>
> Thank you,
> robert
>
>
>
> On 12/20/2015 06:20 AM, Clément Bera wrote:
>>   
>>
>>
>> Hello,
>>
>> I tried to get your document but I got:
>>
>> Dropbox - error
>>
>> Is it only me ?
>>
>> 2015-12-20 11:31 GMT+01:00 Robert Withers <robert.w.withers at gmail.com 
>> <mailto:robert.w.withers at gmail.com>>:
>>
>>
>>     Excuse me for failing to complete this email./ I wanted to ask
>>     for feedback on these structures, especially the header
>>     specification word structure. So these fields make sense?
>>
>>     thank you,
>>     robert
>>
>>
>>     On 12/20/2015 05:27 AM, Robert Withers wrote:
>>
>>         I wrote up the various SecureSession frame types in
>>         presentation document, which you can get here:
>>         https://www.dropbox.com/s/3xfa5oqs8ihj88v/FrameTypes.pptx?dl=0
>>
>>         These are not yet implemented, but it is progressing. Ne quid
>>         nemis.
>>
>>         thanks,
>>
>>
>>     -- 
>>     . .. .. ^,^ robert
>>
>>
>
> -- 
> . .. .. ^,^ robert

-- 
. .. .. ^,^ robert
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