I’ve been delving into SIP telephony lately. It all started when I wanted to have a PSTN phone number in another country. For business reasons, I have carried two mobile phones for the past two years. One has a phone number in the country where I live. The other has an overseas phone number. If anyone in this other country calls the latter phone, the call gets trunked through to me through the magic of GSM global roaming. I answer the call and have the luxury of paying exorbitant global roaming charges while someone tells me about their weekend.

Well, at least my clients in this other country can call me relatively cheaply.

So I thought SIP providers might offer me something useful. The utlimate goal was just to have a number in this other country forward through to my main mobile (the foreign mobile phone provider wouldn’t do this for me). Anyhow, I found a SIP provider and yes they will forward a call through and charge me about a fifth of what the roaming charges were. So thats good.

However, all this SIP stuff is quite interesting. There really is a lot of interest in the Asterisk PBX software. And these ATA devices are interesting pieces of technology. To play some more I’ve ordered one of these SPA 3102 ATAs (analog phone adapters).  More info when I actually receive it.

Of course the biggest killer of internet telephony is latency. If your call is trunked via the USA and you don’t live anywhere near the USA then chances are it’ll all be horrible. My experience prior to now is that Skype is great for internet to internet calls … but not so great if you want to connect to a real phone number. SIP is terrible if you have bad latency.

And as for linux SIP soft-phones. I am yet to find a decent one. I’ve tried ekiga, twinkle, linphone. All of them seem horribly dodgy. When I signed up to my new SIP provider, I found ekiga would crash as soon as the call connected. Twinkle would crash when you hung up the call. linphone I think mostly worked. In all cases, a softphone like X-lite would work perfectly under windows (even in vmware). Generally a bad linux experience. I’m hoping that an ATA will get rid of these problems.