Which providers allow SIP (VoIP) calls over their networks?

Planning on changing phone and contract soon and since my 'landline' and home office line are both SIP it would be nice to be able to pick up calls on my mobile when out and about (e.g. with Gingerbread's built in SIP client).

However often buried in the network's T&Cs there's a 'no internet calls' clause. Anyone know which (if any) UK networks do allow it and do those that say you can't actually block it (e.g. port-blocking) or just complain if you use it too much (the handset itself will be unlocked/unbranded so not blocked at that level)?

I wouldn't be looking at using it excessively (I really only want to prevent missing inbound calls) and wouldn't be on an 'all you can eat' data plan anyway.

I know it'll work over WiFi but would be much nicer if it worked over the cellular network too.

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CTPAHHIK  Jul. 7, 2011 at 14:56

I never tried using SIP on any of my phones. However, considering what you saying about "no internet calls" I don't know of any provider who would be blocking them. Skype by definition is internet call and I don't know of anyone blocking Skype.
Some providers allow unlimited data, which applies to internet browsing, but not streaming. Internet call is streaming and will come out of your data allowance. Does not seem that any provider cares what you do with your data allowance (tethering included) as long as you do not exceed it.
GiffGaff appears to be only exception to the rule due to their convoluted usage agreement. They might block you.

Another thing to keep in mind is that providers do not guarantee quality of service for internet call to be legible. Sometimes it's easier to say that internet calls are not allowed, then explain to customer why their network is crap and cannot sustain low latency 3G connection.

jezcooke  Jul. 7, 2011 at 15:18

Thanks, if Skype isn't blocked then hopefully SIP isn't either. Indeed call quality/latency could be an issue depending on the coverage but I guess worst case scenario I just call them back as a normal voice call.

jezcooke  Jul. 24, 2011 at 11:54

Just partially answering my own question in case anyone stumbles across this thread on google etc. Got my new phone contract and it seems that T-mobile at least does indeed block SIP. :(

CTPAHHIK  Jul. 25, 2011 at 07:52

Works over WiFi, but not over 3G?

jezcooke  Jul. 25, 2011 at 09:00

Works over WiFi, but not over 3G?

CTPAHHIK  Jul. 26, 2011 at 09:35

Can you change ports on SIP app? Don't know which one you using, but I would expect some port forwarding on WiFI router to be setup first, no? Unless you have one that uses common ports. I had to spend a lot of time with router to get Cisco IP phone working. Universal PnP works like a charm, but you don't have this functionality with provider only with WiFi.

jezcooke  Jul. 26, 2011 at 15:22

I'm currently using CSipSimple but intend to use the built in client when GB is officially released for my Galaxy Ace (should be imminent). No setup is required on the router, I'm not an expert on that level of the SIP protocol but I believe it uses the STUN server to traverse the NAT (maybe UPnP is involved too) in any case over my broadband 'it just works'.

When using the cellular network it just fails to register, I haven't investigated deeply why but probably T-mobile are just blocking the standard SIP ports but I can't change these as that would be down the the provider (sipgate).

It's not the end of the world, just would have been a nice bonus had it worked. The main advantage for me of having a SIP client on my phone is that when travelling abroad I can hook up to the hotel WiFi and call home for free with both ends using real phones.


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