CSN.1 directory

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Harald Welte laforge at gnumonks.org
Wed Aug 1 19:58:40 UTC 2018


Hi Benoit,

On Wed, Aug 01, 2018 at 09:34:27PM +0200, benoit michau wrote:

> This email to point to a recent development I made on CSN.1, which
> might be of interest to some of you. 

Thanks a lot for implementing this in the first place, and also for
sharing information about it here.

It's amazing that we finally seem to be getting good CSN.1 tools 


> I extracted and consolidated all
> CSN.1 definitions from 24.008, 44.018 and 44.060 (the "consolidation"
> part was quite hard...). 

I think the biggest problems are the many syntax errors in the official CSN.1
syntax in the specs.  I once tried to parse it from proprietaryt CSN.1 tools,
and it was a nightmare.  In fact, there are companies selling the cleaned up
and fully confirming syntax for money.  

Somebody should submit your fixed versin to 3GPP so they can release a correct syntax at least...

> I have also developped a CSN.1 to Python
> translater, and a runtime to encode / decode any CSN.1 structures.

Thanks.  What we need to figure out now is how to make best use of this from within
Osmocom.  OsmoPCU is - as you know - implemented in C.  Rewriting it in python is
unfortunately not an option, if not alone for performance reasons :/

However, it would be great if we could benefit from your work in other ways, such as

a) for unit testing our code (particularly the hand-written encoders/decoders)

b) for integration testing.  Unfortunately TTCN3/TITAN doesn't have any CSN.1 tools,
   so we cannot use a "trusted, aut-generated" encoder/decoder from our existing
   integration tests.  However, maybe there are ways we can integrate your python
   CSN.1 with TTCN-3? MAybe it's possible to auto-generate ASN.1 syntax  and an ASN.1(BER)-to-CSN.1
   transcoder in python.  Then we could use TTCN3 templates in the TITAN world, and
   we'd simply call a function to encode as ASN.1-BER, and then into your transcoder to create
   CSN.1 from that (and vice versa)?

c) something like a MS-side (E)GPRS RLC/MAC implementation in python.  We could then use this
   over "virtual/simulated" radio against OsmoPCU.

d) maybe generate C / C++ encoder/decoder from your python framework, since it fully
   parses and understands the syntax tree...

I'm not a python expert and I have not used your code yet, so I'm not sure what is
realistic/possible.  But for sure it would be really great to use generated parser/encoders
for CSN.1 in one way or another...

If you (or anyone else) have any further ideas to share, please feel free to do so!

Regards,
	Harald
-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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