Adventures with SIP

Having moved office we decided to upgrade our phone system and route all our outbound calls via Engin (SIP Service provider) after a bit of setup we have everything working nicely, with one exception, outbound calls would drop after about 5 minutes and 30 seconds.

A bit of googling quickly showed that we were not alone, this led me to the following :-

http://whirlpool.net.au/index.cfm?a=wiki&tag=VoIP_engin_5m32

Which explains that Engin (and others) periodically send a re-INVITE request for a number of quite valid reasons that I won't discuss here.

That's all very well but I couldn't quite see why these re-INVITE's wern't making it through my router, I could clearly see that a dynamic NAT entry existed that should have allowed the Engin server to send these SIP packets to my PBX.

So after a bit more sleuthing here's what I found:-

The re-INVITEs are sent from a different IP address to the Engin SIP gateway that the call was initially set up through!!!!

So in my case I re-configured my router to port forward ALL incoming UDP packets with a destination port of 5060 to my PBX and hey presto no more dropped outbound calls.

Finally a universal crimping tool

After MANY years of searching I've finally found a low cost (almost) universal crimping tool.

It's the Molex 63811-1000 (Digikey WM9999-ND), this little beauty will correctly crimp both the conductor and the insulation on most small crimp terminals (not only Molex) and costs just US$50

Deploying VS2005 C++ Applications

IN VS 2005 it seems you can't just drag the library dll's into system32 anymore.

Instead you need to install them using vcredist_x86.exe which you can get here:-

http://www.microsoft.com/downloads/details.aspx?FamilyID=32bc1bee-a3f9-4c13-9c99-220b62a191ee&DisplayLang=en

Of course you can also make an installer with VS if you could be bothered.

Ceramic Capacitor Dielectrics

Not sure which capacitor dielectric is which ?

These 2 tables make things easier:-

Class 2 (Unstable)
Class 1 (Stable)

How to apply schema changes on SQL Server publication databases

Click Here

Kernel Cross Reference

Ever spent hours searching for an obscure function or definition in the Linux kernel ?

Here's the answer:-

http://lxr.linux.no/source/

Jump to it, select the Kernel you're working on and then select "identifier search"

Quick steps to bring up a PPTP connection

pptp <server> user <username> password <password>
route add <server> ppp0
route del default
route add default ppp1