Subject: Re: [rohc] WG last-call for SIP/SigComp

From: Gonzalo Camarillo <[email-masked]>
Date: Sun, 26 Nov 2006 12:36:36 +0200

Hi Adam,

> The proper behavior is actually pretty obvious. If you'd like to spell
> it out, the logic to use is: SIP retransmissions need to be sent through
> the SigComp compressor again. In other words, you don't retransmit the
> already-compressed information; you recompress the SIP message, and send
> the newly compressed message. The reason this behavior is necessary is
> because it is impossible to know whether the failure causing the
> retransmission occurred to the message being retransmitted or to the
> response to that message. If the loss occurred to the response, then any
> state changes effected by the first instance of the retransmitted
> message will already have taken place. If these state changes removed a
> state that the previously-transmitted message relied upon, then
> retransmission of the same compressed message will lead to a
> decompression failure.

so, you assume that the sender will be informed about the successfully 
deleted SigComp state at the receiver by a different protocol message 
than the response that got lost, right?

Thanks,

Gonzalo

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From: Adam Roach <[email-masked]>
Date: Sun, 26 Nov 2006 10:48:09 -0600

> than the response that got lost, right?

No. You don't *ever* get informed about states being deleted; you assume 
such deletions as soon as you send a message that can result in them.

/a