[Asterisk-Users] Cisco 7940 - SCCP or SIP?

[Lex Lethol]

On my experience, you should go to SIP whenever possible.  7940/60 on
SIP will do most if not all fuctions.

Try the little chart on support hardware on chan-sccp.sourceforge.net

Lethol



----- Original Message -----
From: slwatts at winckworths.co.uk <slwatts at winckworths.co.uk>
Date: Fri, 27 Aug 2004 14:16:11 +0100
Subject: [Asterisk-Users] Cisco 7940 - SCCP or SIP?
To: Asterisk Users Mailing List - Non-Commercial Discussion
<asterisk-users at lists.digium.com>

 
Hi All 
 
I have recently downloaded Asterisk and was so impressed I thought I
would setup a home server and I went out and got myself a couple of
cisco 7940's. (and a sipaura 3000!).  thanks to various posts on this
list and the voip-info site I have managed to get chan_sccp setup and
working with the 7940's but the I tried to get the messages, services
and softkeys working. It seems this is where some sort of black magic
needs to be used as I cannot find any way of getting them to work....
which leads me to the main question....
 
Is it better to use chan_sccp or SIP? I know these phones can work in
either mode I was just wandering which is the better format and which
has the most functions implemented?
 
Its a simple home environment that I am planning but it would be good
to be able to use the softkeys to transfer calls and to pickup
messages.
 
Thanks in advance, 
 
Sam 
 
Kevin Walsh <kevin at cursor.biz> wrote on 27/08/2004 13:59:09:
 
 > Michael Manousos [manousos at inaccessnetworks.com] wrote: 
> > Kevin Walsh wrote: 
> > > Michael Manousos [manousos at inaccessnetworks.com] wrote: 
> > > > a) The transmitter detected silence and sent nothing but the last CN 
> > > > packet was lost. According to the above interpretations, the receiver 
> > > > will try to conseal a packet loss, which is wrong. 
> > > > 
> > > 
> > > I would propose that after x lost packets, Asterisk should treat 
> > > all further lost packets as CN.  The proceeding x packets should be 
> > > interpreted as RTP packet loss and run through the concealment routine. 
> > > 
> > Well, no matter what kind of concealment algorithm is used, just the 
> > first one or two packets will be concealed. The rest losses will result 
> > in no-playback. No CN interpretation, just absolute silence. 
> > 
> That's true - unless there's some logic to say that after x lost 
> packets, the line state should switch to CN generation instead of 
> silence. 
> 
 > The line state would switch back once a fresh RTP packet is received. 
> 
 > > > > 
> > > > b) The transmitter sent an RTP packet, that packet was lost and the 
> > > > last packet correctly received at the receiver was a CN packet. Again, 
> > > > following the above interpretation, the receiver will do nothing (or 
> > > > more accurate, will play some background noise), while it should 
> > > > conseal the packet loss. 
> > > > 
> > > In this case, there is nothing to conceal anyway, as the last received 
> > > data was a CN packet.  In this case, the CN state should be continued 
> > > until an RTP packet is received and the line state can be changed. 
> > > 
> > Exactly. So the receiver, in case of no-receiption, should go back and 
> > see what was the last packet correctly received and act as I described 
> > above. 
> > 
> Maintaining an audio state flag (CN/RTP) would be the key here. 
> 
 > > > 
> > > The difficult part to handle would be late or out-of-sequence RTP 
> > > packets.  These should be ironed out by the jitter buffer.  Late, 
> > > lost and juggled packets are to be expected when dealing with UDP. 
> > > 
> > Actually this is not so difficult, if there is a jitter buffer. 
> > 
> Right. 
> 
 > -- 
>    _/   _/  _/_/_/_/  _/    _/  _/_/_/  _/    _/ 
>   _/_/_/   _/_/      _/    _/    _/    _/_/  _/   K e v i n   W a l s h 
>  _/ _/    _/          _/ _/     _/    _/  _/_/    kevin at cursor.biz 
> _/   _/  _/_/_/_/      _/    _/_/_/  _/    _/ 
> 
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