The big news last week was how AT&T Well apparently, AT&T must read my blog or something, because once again SIP port 5060 is blocked. I tried siphon on my iPhone this morning and now it won't register. I tested port 5060 and it is indeed blocked. Alas, so no more SIP calls using siphon.
The AT&T Overlord giveth, and the AT&T Overlord taketh away. 
Hey FCC, can you give AT&T a little smackdown for me please? Just last week AT&T announced it was allowing VoIP over 3G, so why the inconsistency? Is it because siphon is a jailbroken app and not an "official" iTunes app? I doubt it. I doubt AT&T is able to detect what iPhone application is making an outbound connection. That would be a form of spyware if AT&T knew exactly which iPhone applications you were using. So seems to me that AT&T is still blocking VoIP calling over their 3G data connection. AT&T is talking a big game about being "open", but they aren't backing it up. I'm sure they'll blame it on some network glitch or something. AT&T could be dragging their feet on allowing VoIP over their 3G network hoping the mere "huge" announcement of support for VoIP over 3G will get the FCC off their backs. It's time for the FCC to stop AT&T's stalling tactics. I want my mobile VoIP freedom and I want it now!
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Are you sure this is not gizmo5 specific problem and not ATT blocking anything? Siphon works fine with other voip clients eg jumblo.com, actionvoip.
If AT&T has changed the decision then It will be big disappointment for me. I need to call abroad too often for the business reasons. I'll have to go for spend some money behind it.
I'm not using gizmo5 for my SIP server. I'm using siphon to connect to an Asterisk-based IP-PBX.
I have to agree with jeze earlier, are you sure it's not a problem outside AT&T's network? I, too, am using an Asterisk PBX and am able to register with a mobile SIP client. Dialing out and receiving calls both work as expected.
this is too bad. But if you think about, AT&T would lose alot of money if they allowed it. All providers have a hidden Monthly minute plan that is about 300 minutes [per month and is very cheap. the only way to get this is to call and explain to them why you dont need the original plan because its too many minutes, and so if VOIP was allowed alot of people could ask for that and use VOIP for all there minutes while paying very little.
Makes sense, but still would love to see this happen.
>>I, too, am using an Asterisk PBX and am able to register with a mobile SIP client.
I assume you mean VoIP over 3G. Please confirm.
It's possible AT&T in certain areas is allowing VoIP over 3G. I can tell you for a fact that they are now blocking port 5060 in CT. As a simple test I mapped the default Remote Desktop (RDP) port 3389 to port 5060 on my PC. Then I used a Remote Desktop client app on the iPhone to connect to my PC using port 5060. The iPhone RDP client wouldn't connect. I changed my port to something other than 5060 and it worked.
There is no other explanation other than AT&T specifically blocks port 5060.
See my other related article, which discussed how port 5060 worked in Los Angeles but not Connecticut. http://blog.tmcnet.com/blog/tom-keating/voip/att-grants-us-mobile-voip-freedom.asp Perhaps AT&T is once again blocking port 5060 in specific geographic regions.
Well go frickin' figure. I just tried siphon again this morning and it's working. I guess AT&T must be messing with their network or something. I swear port 5060 was blocked on 10/12.
All is well. The AT&T Overlord has heard my cries and once again opened the door for mobile VoIP freedom...
Interesting,
With all the confusion in the VOIP over mobile arena, there is a much less costly option which is just coming to market, Cellular Over Internet Protocol where you get local network dial tone on any cell phone.
This is the better solution on all fronts, first, any phone can be used, not just GSM smart phones like all the others, plus no additional data plan charges, never mind current TOS denies use of data network for voice, as in VOIP applications, so it makes you wonder what is going on?
COIP is not a band width hog like VOIP over data is, so another plus given peak bandwidth is upon us, just look at how AT&T couldn't support iPhone 3GS applications, and this is a problem with all carriers now, or in the near future, so I vote for VOIP-COIP.com as the best solution, especially for international calls worldwide, something not possible with VOIP over mobile.
Add in WiFi, WiMax and you have a solution for everyone, just makes sense to me. VOIP-COIP.com
That's pretty disappointing, and it is true, AT&T always mess up with their VoIP servers. I used to had AT&T, but i fed-up with their 24X7 busy server and congestion. I tried several other services too, but i found one from www.spiderstar.com convincing. I fixed this a month before, I am happy for not facing congestion since last one month.