[rohc] [SigComp]Shared mode and some other SigComp-state related stuff.

["Gustav E" <gustav_kung at hotmail.com>]

Hi all.

Since I'm fairly new to this list and SigComp in general, I have a few 
questions:
1. Regarding Shared mode: What became the consensus of the previous 
discussions on the list? Is the general somewhat simplified recommendation  
to only "allow" a compressor to create one shared-state?
2. State memory: If  compressor A for any reason creates a local state, 
valid only in one compartment, should the size of that local state be 
considerad to use any of the available State memory in A? I'm guessing that 
it should, simply writing the question to be assured.
3. USD. I fully understand the usage of a USD. However, I do not understand 
if a USD-state should be treated any differenty then any other state created 
at the remote end. Is a USD per definition a shared state? I'm guessing that 
it must be if the sending compressor is to have any advantage of the 
USD-state at the remote end. Then, again, should the USD-state (local state) 
at A be considered to occupy State-memory? Should it be considered any 
differently then any other shared state?
4. General shared-state issue: 3321 states that shared-state is an 
uncompressed message. Is the recommendation to only use complet uncompressed 
messages as shared state? What about parts of messages or even other 
textual-protocol-specific data?
5. (Little bit off-topic, PoC specific question): In the PoC NEMS Signalling 
Spec. "Signalling flows (UNI) v2.06", a procedure for establishing a USD is 
described. Among others it states that the four first bytes of the 
state-value should be "usd1". Can any helpful individual explain to me what 
the purpose might be? Should either local or remote endpoint take any 
specific action here?
The spec says:
"For USD identification it is important that the identifier string is placed 
in the beginning of the state_value of the USD, therefore special attention 
must be paid in the case of large USD as the UDVM has a circular buffer."
I do not understand the purpose here..

Appologies for all these questions. Simply hoping to get some sort of 
clarifications here.

Best Regards,
/Gustav E

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