VoIP headaches

I've recently signed up with PennyTel to get better prices on phone calls. This was after two relatives of mine both recommended PennyTel and said how easy the whole thing was to set up when using a Linksys SPA-3102.

OK, so I signed up and purchased the Linksys device. I set the networking stuff through the phone then followed the guide on the PennyTel website to configure SIP (VoIP connectivity stuff). I was feeling pretty good about the whole thing, that is until I made the first phone call!

I thought I'd try to impress a mate so I called up one of my tech savvy friends and told them I was using VoIP to talk to them. The quality sounded quite good, then after 32 seconds the call dropped out! I had called a mobile so I thought it may just be a glitch. The next two calls resulted in the same drop out after 32 seconds. By this stage my friend thought it was quite amusing that my new phone service was so unreliable after I had been boasting about the cheap call rates!

After hours of Googling and messages back and forth between PennyTel support, I still hadn't managed to avoid the call drop out, or another intermittent problem where the SIP registration was randomly failing. The settings looked fine, and PennyTel didn't appear to have any outages as I tested things with a soft phone from another DSL connection. I was really regretting the whole thing, and getting pretty pissed off. I had a think about the whole scenario, and the only thing I hadn't eliminated was my DrayTek Vigor 2600We ADSL router. I had already set the port forwards required for the Linksys SPA (UDP 5060-5061 and 16384-16482) so thought nothing more of router configuration. As a last resort, I searched the Internet for people running VoIP through their DrayTek to see if any incompatibilities existed. I came across a site with someone experiencing my exact problem, and they had a workaround! It appears that the 2600We has a SIP application layer proxy enabled by default. This really confuses things on the Linksys and has to be disabled. After telnetting to the device and entering the following command, things were working great:

sys sip_alg 0

Note that you may need to upgrade your DrayTek firmware for this command to be available.

After the changes I made some calls and no longer got disconnected after 32 seconds! Woohoo! At the end of the day I'm glad I chose VoIP for the cost savings, even though it caused me grief the first few days.

Update: One other setting I have found needed a bit of tweaking was the dial plan. Here is my current Brisbane dial plan for an example:

(000S0<:@gw0>|<:07>[3-5]xxxxxxxS0|0[23478]xxxxxxxxS0|1[38]xx.<:@gw0>|19xx.!|xx.)

Learning more about EFI systems

I've been interested in the inner workings of cars and engines for a few years now, in particular engine management systems. One project that has my attention is MegaSquirt which is an Electronic Fuel Injection controller intended to teach people how EFI works. I've decided to get in on the action, but since my soldering skills are a bit rusty I'm starting with the MegaStim kit (much easier to build) which is a small diagnostics device used to test out MegaSquirt hardware. I purchased the kit from DIYAutoTune.com and I was impressed with the service, I'll get the rest of my MegaSquirt gear from them for sure. Even if I don't end up using MegaSquirt for anything, I'm sure it will still be worth it for the experience.

Fight against dirty wheels

I don't know what it is with European cars but most of them come standard with brake pads that love to totally cover the wheels with carbon. I've attached a picture of what my wheels look like when it's been a couple of weeks since the last wash. Next service I'm supplying a set of EBC Greenstuff brake pads which should hopefully put an end to this problem, I'll keep you posted.

Keeping up with multiple Blogs

After a quick search for RSS aggregators, I found Google Reader to do exactly what I want. It saves so much of my time monitoring RSS feeds from a central location, and being web-based means I can access it from anywhere. In case you are wondering, I don't work for Google!

Update: Since publishing this, I've had a few people tell me how much Google Reader sucks compared to the alternatives out there. Greg Black recommended Bloglines to me, and after giving it a go I must say that it's a much better solution. Looks like I'll stick with this one for a while.

Dealing with Japanese imports

A number of my friends have recently purchased Japanese cars. One of the minor issues that is often overlooked is the lack of ability to tune into any FM radio stations above 90MHz. Since I was working on one of these said cars this afternoon I thought it would be a good time to mention this problem. Among other things, be prepared to replace the stereo if you import!

Even into taking these things into consideration, Japanese imports are still great value! You get way more car for your dollar.

Interesting Microsoft disclaimer

Hotmail's disclaimer caught my attention whilst I was troubleshooting an Internet connection using netcat. Looks like they're either hiring the Mafia to do their dirty work, or taking matters into their own hands:

Violations will result in use of equipment located in California and other states.

This disclaimer is displayed when you first connect to the SMTP port of mail.hotmail.com. I have no idea what kind of torture the disclaimer implies but I'd rather not find out!

Other efforts to stop Spam

Watching the logs closely after my Greylisting install made me notice just how many attempts are being made to deliver junk to my mail server. I thought I'd add some a few more checks to Postfix so the messages don't even make it to the Greylisting stage. The most effective ones are; requiring a fully qualified HELO string (you'd be surprised how many Spammers just use HELO localhost), and checking that the sender exists before accepting the message. This is done with reject_non_fqdn_hostname under smtpd_recipient_restrictions, and reject_unverified_sender under smtpd_sender_restrictions respectively. A good guide on how to set up sender verification can be found on the Postfix website.