SIP VoIP Clients for the iPhone

Apple has given the green-light to permitting Voice over IP applications on the iPhone (and iPod touch) handhelds through the App Store; so long as 3G and EDGE connectivity is blocked of course.  This means you are limited to connectivity through WiFi only, which is still pretty cool!

Although similar in that they are both VoIP applications, a Skype client is different than a SIP (Session Initiation Protocol) client.  A Skype client only works with Skype’s voice services network, whereas a SIP client can connect to virtually any SIP-enabled PBX, including Cisco, ShoreTel, and Asterisk.  This allows you essentially make and take calls from your work extension on your iPhone, even when you step away from your desk.  You can also call local extensions without having to use full DIDs.

So far, I have played with 3 SIP applications for the iPhone:  fring, SipPhone for iPhone, and WeePhone.  These three seem to be the major three applications available in the iTunes App Store as of the time of this writing that can connect to any SIP server, and are not locked to a single hosted provider.

I have tried to add all of these applications to both an Asterisk system and a ShoreTel system.  Mind you this is not thorough testing, just some basic setup and trials.  Asterisk seemed to more or less work, whereas integration with ShoreTel is still very rough.  Common to all applications is mixed mileage for successful calls and very rough GUIs. Here is a breakdown by software application:

fring

fring (free)
The first application I tried a few months ago is fring.  It is primarily designed to work with their IM/voice service, then they layered SIP, skype, and other communication gateways as “Add-ons”.  You must set up a fring account to use the “add-ons”, which is free, but still annoying.

I tested this with an Asterisk server, which seemed to work alright in terms of call setup and teardown, but the audio was next to unintelligible.  Audio was tinny, very delayed, and ultimately just unable to support a reasonable conversation.  This may have changed, and I have not yet had a chance to try with any new versions.

SipPhone for iPhone

SipPhone for iPhone ($6.99)
I was inspired to set this software up with my ShoreTel IP-PBX after watching a video tutorial by “Dr. VoIP” that walked through the steps of setting up this software with a ShoreTel IP PBX.  I purchased the software, performed the configurations, and on my first call, my iPhone completely crashed to the point that I had to hard reset it.  Not off to a good start!

I placed a few more test calls and had intermittent success.  Oddly, I was able to call outbound numbers without any problem, but local calls would crash the phone.  I did a packet capture on the network and evaluated the SIP traces and could not see anything that would wreak havoc on the network.

On calls that did work, audio is bad.  The iPhone audio comes in really tinny, and the person you called hears a lot of crackles, which is bad enough to really annoy the other party.  I think this is a codec negotiation issue and the usage of alaw vs. ulaw (causing similar results in previous experiences).

On the Asterisk system, call setup and tear down worked consistently (ie didn’t crash the whole thing), but the audio problems remained.

Of note, I discovered this software used my old SIP stack friend: PJSIP.  Props for that, now just fix the bugs!

All and all, this application seemed to have the most configuration sophistication with multiple account support and even some digit prefixing ability to make your contacts actually useful (ie, dials 9 ahead of a contact’s phone number so the call goes out).  Apparently the iPhone 3.0 version is much more stable and provides additional features like the ability to receive SIP calls even when the application is not active (niiiiiice).

WeePhone

WeePhone ($4.99)
There is something to be said about an app that keeps it simple and is in-tune with its title like “Wee”phone.  It is tiny and very basic.  The GUI is very basic/rough, yet functional.  For my brief testing with the ShoreTel system, I had perfect quality, nearly zero latency audio, in one direction… On the Asterisk system, however, perfect audio quality with virtually no latency.  Clearly these guys figured out the audio issue and have it working great.

Of course, where this application excels and the others fail, this app fails where the others shine.  Call control was rough and inconsistent.  Outbound calls (INVITEs) sometimes just didn’t seem to make it out, and hangups (BYEs) would sometimes not make it there either.  From my very early synopsis, it seems like the application doesn’t queue SIP messages properly.  For instance, the Asterisk server would send a lot of NOTIFYs to WeePhone while I was trying to place a call, and the call just wouldn’t happen.  Seems like a little bug that can be fixed pretty easily.  But man, the audio was great

Summary
So, although there are some options out there (of which there were zero less than a year ago), these applications are still in beta phase.  Putting any of these apps in a production environment for users is suicide, so save yourself some time and just buy a DECT SIP phone if people want to be mobile around the office.

The software will get there when these developers take the time to harden these applications and clean up the GUIs, but for now, they serve as fun/frustrating geek toys/projects.