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Re: [Linphone-developers] ZRTP Linphone<->CSipSimple

From: Werner Dittmann
Subject: Re: [Linphone-developers] ZRTP Linphone<->CSipSimple
Date: Thu, 07 Mar 2013 08:01:48 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130105 Thunderbird/17.0.2

Am 06.03.2013 19:06, schrieb Sami Farin:
> On Wed, Mar 06, 2013 at 18:15:01 +0100, Werner Dittmann wrote:
>> Some remarks from my side:
>> I assume this log is from Linphone.
>> the connection seems to be slow because quite some retransmits of packets.
>> According to the info both clients had a ZRTP connection some time before
>> (RS match found).
> ZRTP retransmission scheme is aggressive.
Yes I know, I did the ZRTP stack implementation and the computation below :-)

>>From rfc6189:
> A Hello message is retransmitted 20 times before giving up, which means the 
> entire retry
> schedule for Hello messages is exhausted after 3.75 seconds (50 + 100 + 
> 18*200 ms).
> Retransmission of a Hello ends upon receipt of a HelloACK or Commit message.
> I saw two transmits before it gave up on ZRTP or something else happened,
> hard to say, ten layers of complexity :)

So, Linphone gave up to send or was it CSipSimple?

>> On the second part (CSipSimple to Linphone):
>> what does "***no more ZRTP chatting!*** mean? Not more data exchange over 
>> the RTP
>> connection between the two clients? Or only no more ZRTP packets? Audio 
>> packets?
> In the logs there no more "ZRTP" words.  I don't know if there ZRTP packets,
> though :)
> After that the connection worked OK without ZRTP enabled (CSipSimple said in
> log "Crypto-suite: (null)".  Both of them decided not to warn user.

That's a bad UI design then - if ZRTP fails the UI *shall* report this to the 
Other client that use ZRTP do this in big bold letters



Werner Dittmann    address@hidden
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