harishankar

I just want to know how SIP telephony works and what the difference is between this type of telephony and something like Skype.

I ask because this has not really become popular but everybody seems to be talking about Skype.

Are there any special requirements to use VoIP with SIP?

I am very new to this technology and I wanted some users' experiences.

GNU-Fan

SIP as it stands is just a protocol, that means, a set of rules so that the software on different computers know how to talk to each other. The difference to the protocol Skype uses is that SIP is an open protocol (i.e. everybody is free to get to know and implement it in its own software) whereas the Skype company takes great efforts to keep their protocol secret. Therefore nobody except this company can tell what data is being transmitted.

The result is that there is just one single Skype program but several programs that understand SIP, such as List of SIP software - Wikipedia, the free encyclopedia

The latter should all be able to talk to each other, provided the SIP was implemented correctly.

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harishankar

Thanks. I was just wondering what were the requirements to chat to somebody after installing an SIP phone client software.

Does one need to set up a server or something? I am sure there must be howtos on this topic available,

Are there service providers for such a service or can we use SIP as a peer-to-peer protocol requiring just the IP address of the other machine? I've searched for SIP howtos online but I've not got this specific information.

GNU-Fan

Basically, yes, SIP needs a server to function. At least, to establish the connection.

If you and a friend just want to twaddle a bit and if you know the peer's IP, there may be simpler and more lightweight alternatives. (direct peer to peer voice chat).

However, it is not you that needs to set up a server, because there are many providers, several of them granting free access to their services. For example, assuming you will use Ekiga ~ Free your speech. as your SIP client of choice, you would probably go registering on ekiga.net in order to get your "telephone number".

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harishankar

Thanks.

I guessed that would be necessary but I wasn't sure. I should actually try direct VOIP and see if that's a good alternative.

Otherwise both ends need to register with the same provider to chat which I suppose can be arranged, but might be a bit of a nuisance.

GNU-Fan

This is not entirely correct. Actually, it goes in some cases as far as that one can call a friend on his "real" phone via such an client. This "bridging" of different protocols is called "peering". But this depends heavily on the particular circumstances of the provider, software, country, etc. So, no general statement can be made here except that it is rarely cost-free.

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harishankar

This was what confused me. Thanks for clearing that up.

Does this mean that two people with SIP addresses obtained from different providers can chat for free, of course depending on whether the service provider is free or not?

GNU-Fan

There are always greedy companies which try to bind customers by denying them free choice, but generally spoken, yes.

From the ekiga FAQ.
Calling - Ekiga

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v1d1t

I think the only reason for skype being so talked abt is that the skype ppl are there to manage and allocate the resources for enabling the voice chat easily. They also have some propriorty protocols to keep the QoS for a very high quality.
Whereas SIP telephone are standalone installables with no well know servers managing the voice resources. It is very successful in case of ppl wanting to talk between the same lan , but outside the lan ... it may be hard to address the exact PC.
A solution to this may be to enable a PBX as an entry point to local lan, then again it will not be possible for a single standalone to build such a system. This can be attributed as one of the reason.

harishankar

Thanks a lot for all your help. I'll definitely look into this.

I now need to figure out whether it's legal to use VOIP in my part of the world also.