Subject: [rohc] Questions on draft-ietf-rohc-sigcomp-sip-08

From: "Vavilapalli Srikanth-A19563" <[email-masked]>
Date: Thu, 6 Dec 2007 22:32:07 +0800

Hi
 
I have few doubts in draft-ietf-rohc-sigcomp-sip-08.txt draft. Can any
one clarify them? Appreciate ur help in this regard.
 
1. Section 4.4: 
 
It also implies that the compressor need not make use of the methods
detailed in Section 2.4 of [RFC4077] (Detecting Support for NACK). for
example, it can use optimistic compression methods right from the outset
---------> Can u please elaborate more on this statement. Does this
statement mean that the compressor shall not wait for the ACK for each
state request it asked to create?  
 
2. Section 5:
 
Applications MUST NOT mix SIP messages and SigComp messages on a single
TCP connection ------> May I know the trigger to impose this
restriction? What are the problems with multiplexing SIP and SIGCOMP
messages? 
 
If a SIP implementation has reason to send both compressed and
uncompressed SIP messages on a single TCP connection, the compressor can
be instructed to use these bytecodes to send uncompressed SIP messages
that are also valid SigComp messages.------> What is the scenario here?
When does an endpoint require to use a NULL compression algorithm? As
per RFC 3486, A client MUST NOT send a compressed request to a server if
it does not know whether or not the server supports SigComp. So the
first message shall go as uncompressed in any connection and later on
compressed messages will be sent if the endpoint discovers that remote
supports sigcomp. In such scneario, are u suggesting that end point
shall open a separate new transport connection between the endpoints to
send the compressed message? If so, what is the need for NULL
compression. The end compressor can use a standard algorithms as well.

Thanks&Regards
Srikanth Vavilapalli

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