Why Does Google Hate SIP?
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I mean, c'mon, Google is building SIP support directly into their phone OS. They aren't against you. Be patient.
Salt on a wound; ugh.
According to this [1], SIP support already exists in Android 2.3. I don't know how far this "support" goes (I suppose it's not hooked up to the Google Voice app, at least). And I wonder how many carriers, once they are shipping Android 2.3, are going to leave that code in place and accessible to the user.
I don't want to be too much of a conspiracy theorist here, but I do wonder if Google is dragging their feet on SIP support because of conflicts of interest with Android.
[1] http://android-developers.blogspot.com/2010/12/android-23-pl...
Some time ago, AT&T accused Google of violating telecom regulations by blocking access to certain high cost numbers[1]. Google was able to defend against the accusation by pointing out that they did not actually provide a telecom service, as usage of Google Voice required a normal phone line[2].
I suspect that if (once?) Google provides SIP support, this distinction can no longer be made. What would be the difference between Google Voice and any other SIP provider?
[1]: http://www.att.com/gen/public-affairs?pid=14048&goback=g...
[2]: http://googlepublicpolicy.blogspot.com/2009/09/response-to-a...
Google's open XMPP-based Jingle protocol does a much better job at common use-cases. Unfortunately there are only few applications that support it (although Google released the relevant parts as open-source).
Simply because the SIP protocol looks simple and is easy to inspect... a lot of hardware/software will get it wrong. And I mean wrong like not implementing some feature on the phone thus bringing the common supported feature list down, implementing ICE in a wrong way then dropping the product support, breaking basic SIP transactions in a way that the phone doesn't even work without a NAT, etc.
Then router producers come in saying - we're doing home routers - let's help and solve it by doing SIP-ALG and active rewriting on our side. And they get it wrong again. And then they don't think of implementing a way to disable the SIP-ALG (looking at you speedtouch).
All the protocols are there. As long as you stick to one single manufacturer, it's ok. As long as you don't need custom features, it's ok. It's when you want to be good to everyone and support everything - then SIP networks fail because you simply cannot support everything at the same time.
Noone tries to analyse Skype and they control all the clients and servers. Whatever problems they create - they can solve. That's why they do better in many cases. Because you can't even "try" to fix their traffic.