From the Developer's Desk

 

Analogue Card end of call detect/hand-up

We've had a lot of calls about end of call detection on the Digium analogue cards and we wrote a patch for Asterisk a while ago which has been included in Asterisk 1.2.x. So if you are running Asterisk 1.2.x the you can just add this to your zapata.conf

For Cape Town:
busydetect=yes
busycount=4
busypattern=500,500
callprogress=no

For Johannesburg:
busydetect=yes
busycount=2
busypattern=2500,500
callprogress=no

To test, do the following:
dial out from a soft phone. Have the person on the other end (telkom side) hang up the line. After a few repeats of the beep-beep tone, Asterisk should disconnect. if it doesn't work, test the "other" busypattern/busycount values.

opermode
Your wctdm module should be loaded using the "opermode=SOUTHAFRICA" option.

So for example on my system I have "options wctdm opermode=SOUTHAFRICA" in my /etc/modprobe.conf.
(Exactly where you put this will depend on your distribution)

ECHO! Make sure that you aren't sending audio out too loud

Too loud outgoing audio will result in echo, and veryloud audio will make distortion and VERY nasty sounds both for you AND the other end.

Use txgain= in your zapata.conf to adjust audio level downwards. txgain=-6 means 6dB softer. Use more or less as required.
In the zaptel source you can "make ztmonitor" and then go "ztmonitor 1 -vv" to see visually and numerically the audio level on channel 1

Make sure you are using the echo canceller and the best one.

Make sure you have echocancel=yes, echocancelwhenbridged=yes, echotraining=800 in your zapata.conf for the channels.

When "best effort" means "least effort"

Connection-Telecom will be strongly promoting the use of Voice over IP, including Voice over the Internet. Therefore, we've been listening with interest at what the large ISPs have to say about VOIP. But we've noticed something alarming - that some ISPs have started redefining a well-known English phrase.

The phrase I have in mind is "best effort".

Think about that phrase, and its meaning in ordinary english.

I'll wait whilst you do that.

Now: when your ISP uses that phrase, listen carefully: "Well, understand that the Internet is best effort" - what they are trying to imply is that it isn't dependably good enough. They need to make this implication because they are trying to sell MPLS and VPN services. In reality, THESE services are now their "best effort" services. Their Internet access services are actually now "least effort".

Do you think that Internet access customers realize that the service they buy is now the "poor relation" traffic on their ISP's network?

ISPs thinking about MPLS and QOS always choose to delude (?) themselves that these techniques will allow new products at higher prices. They seem to fail to notice that existing customers may realize that they are being asked to pay more for what they should always have been getting. Or that customers who stay on the standard products may realize that they are getting a worse service and expect a corresponding price reduction.

IP has always been described as "best effort" - as an attempt to explain the approach taken to error recovery in IP, particularly in contrast to older protocols like X.25. X.25 does error detection and retransmissions at every layer of the protocol. TCP/IP does none in the IP layer, and leaves it all for the TCP protocol.

Well run IP networks drop an extremely low percentage of packets: A large international ISP guaranteed a maximum of 1% and usually achieved 0.2% or so.

But "best effort" has never before meant "deliberately drop packets in order to make way for other people's traffic".

The technical meaning of "best effort" in IP networks used to be the same as the ordinary english meaning. Now it's being twisted to mean the opposite.

This all matters to you if VOIP is in your future. Will your ISP's network support your VOIP traffic properly? If they don't seem sure, perhaps you should encourage them to make their "best effort" for your traffic!

With regards,
Steve

:wq