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

[slwatts at winckworths.co.uk]

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
> _/   _/  _/_/_/_/      _/    _/_/_/  _/    _/
> 
> _______________________________________________
> Asterisk-Users mailing list
> Asterisk-Users at lists.digium.com
> http://lists.digium.com/mailman/listinfo/asterisk-users
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users
--------------
Winckworth Sherwood Solicitors and Parliamentary Agents 
DX 148400 WESTMINSTER 5 : 35 Great Peter Street, London SW1P 3LR
Telephone 020 7593 5000 Fax 020 7593 5099

-Confidentiality- 
This email message and any attachments are confidential; they may be subject to legal professional privilege and are intended for the named recipient only. If you are not the named recipient, please return the message and enclosures immediately and delete them from your system.

-Caution- 
Before advice received only by email (whether by attachment or otherwise) may be relied on, the authenticity of the communication must be verified by means independent of email.

-Regulation- 
The firm is regulated by the Law Society. 

-Partners- 
A list of partners is available for inspection at each office of the firm and on the firm's website at http://www.winckworths.co.uk
 


-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20040827/ddab171a/attachment.htm