Not your father’s VoIP

What makes Voice-over-Internet (VoIP) potentially disruptive this time around, compared to all prior attempts, is really that there is now a standard allowing VoIP services to interoperate over the Internet directly, without ever hitting the traditional telephone network (PSTN). This standard is called SIP, Session Initiation Protocol. It’s not important to know technically what SIP is. It is only important to know that it enables the kind of interoperability and interconnectivity we have come to expect from the Internet.

In the past, VoIP services where characterized as PC-to-PC or PC-to-Phone. In those days, PC-to-PC meant users on VoIP service A could call other users on VoIP service A. If another user was on VoIP service B, there was no way for the two to talk, unless they both upgraded to a PC-to-Phone service, essentially using the PSTN as the interconnect. Today, using the SIP standard, users on VoIP provider A can communicate with users on VoIP provider B, directly over the Internet. The media has not yet grasped the significance of this and they still report about VoIP in the same old terms, still considering the traditional PSTN as the means to interconnect.

Because of standards, users on Internet service A can communicate via email with users on Internet service B. Likewise, now that interoperable standards exists for VoIP, users on VoIP provider A can place calls to users on VoIP provider B, if both provider A and B operate interoperable SIP-based VoIP services. This is as it should be. That’s how we expect the Internet to work. We don’t need the PSTN to communicate with each other if we are both using VoIP services. Would we sign up for an Internet service provider that only allowed us to exchange email with other users on the same service, or charged extra for sending such email? I don’t think so. And there will come a day when we will not use VoIP services that only let us call other users on the same service, or charge extra to call other users on other VoIP services.

But the media doesn’t get it yet. They should be telling us which services are based on SIP-standards, which ones support standard SIP hardware/software as opposed to requiring propriety hardware/software, which ones support inter-provider calling, which ones support future standards like ENUM, and, just as importantly, which ones are closed systems with no inter-provider connectivity like the services of days gone by.

Below is a list of free services that support SIP-standards:

Using any of the above VoIP services, allows you to call anyone on the same service as well as people on any of the other VoIP services listed above, and even anyone on the Internet with a SIP address/number, which includes a rapidly growing number of corporations, universities, and smaller service providers not listed above.

Other so-called VoIP services, such as Skype and Voiceglo, DO NOT allow calling to anyone outside their service over the Internet. For example, a Skype or Voiceglo user cannot call a SIPPhone, IPTEL.ORG, or FWD user, but IPTEL.ORG, SIPPHONE, and FWD users can call everyone except a Skype or Voiceglo user. Skype and other non-standards-based services are essentially VoIP islands, excluded from the open SIP VoIP community.

When picking a VoIP provider, be sure to ask if they support the SIP standard, whether they use standard SIP hardware/software (soon to be available at your local Bestbuy), and whether they interoperate with other SIP-based VoIP providers. It may not matter to you that much right now, but it will matter a great deal in the not so distant future.

19 comments for “Not your father’s VoIP

  1. Thanks for a very straight and clear explanation of the importance of free standards in VoIP.

  2. I was about to download Skype after reading about it in some mag. Decided to google for user comments first and stumbled upon your cry for standards. Thanks very much. No Skype for me

  3. Thank you for a very concise article. I couldn’t agree more.

    VoIP represents the future of telecoms, and, frankly, it’s about time an open source standard was allowed the opportunity it deserves to become truly mainstream.


  4. It really mtter how SIP actually works and whats the cost of the SIP phone. And why do you need a piece o extra hardware when your computer can do the work. WHen you figure ot how the technology of P2P telephoney works compared to SIP then you realised that how much better the quality of ther service is.
    Seriously ask yourself this question… when u use a skype out to call phone, how much are u investing in the technology? Nothing at all!!!!! except from the 1cent per minute call… And the P2P technology allowed even kid to set up the system!!! why do you want big VOIP organisaton to convinced you to buy their expansive hardware and subscription!!! I dun get it!! ANd because the resources are only utilized by both of the end -users, thats why the quality of the sound is very clear… and it allows a growing users’ database without a a disruption in quality. Please check out the fact.
    I ma not sure what Skype is doing correct by making the technology proprietary, by if u really look closely to it… they will not make much proft from the whole thing at all…because it is going to be dirt-cheap! Thats is reason Big corporation never come out with this technology because its doest earn them any super profit at all. Its only renegade company such as skype who eill come out with such a product.

  5. Edward, below are my responses. (1) All the providers I mentioned offer FREE SIP service including free SIP softphone software, so one does not need extra hardware or a subscription (any more than one must "sign-up" for Skype). (2) There is nothing about Skype that makes it more or less peer-to-peer than SIP. Skype requires a "bootstrap" set of hosts. In fact, with the super-node model, a Skype call may take a far less direct route than a SIP call, in practice. (3) I will give you that Skype is quite easy to set up, and I hope that the SIP software gets better in this regard. (4) I’m not concerned with companies making profit. I am more concerned with ‘free as in speech’ than I am with ‘free as in beer’ in this case.

  6. I need some advice on where i could find a comprehensive list of SIP-based VoIP providers (does not have to be free). Thank you for your short list, I just want to see more, if possible! Thank you in advance.

  7. Mr Blog, in your comment of 7 July 10:52 you say "bootstrap set of hosts" and "Skype’s super-node model".

    Here’s what I don’t understand.

    I’ve had a look at the Skype site and am wondering what the super-nodes do for you when you are placing a call. Are they only for IP look-up?

    In that case, the RTP stream would go direct to the target, once the call was set up. If they are relaying RTP, then why are they?

    The difference between call set-up and the audio stream gets confused on the Skype site. Maybe they intend it. Can you clarify this for me?

  8. Baldemar, I doubt that it’s comprehensive, but there are many services listed at the SIP WIki:
    The Voip wiki also lists many sites:

    Andrew Kurn, Skype specifically forbids users from reverse engineering their protocol, so unfortunely even if I knew those details about the Skype protocol, I’m not supposed to tell you. This gets to the root of a major problem I have with closed proprietary protocols in the first place.

  9. The problem I find with these free sip providers is that none of them integrates with the PSTN. I mean how good is this if you are still in an island. Sure, with SIP the island is bigger, but we need some of these providers to get gateways to the PSTN and charge these calls.

    In addition, it’s not SIP that makes theses services free, yes SIP helps a lot because these services are now open. But I am sure all of them are waiting to reach critical mass before they can start making some profit out of this. They are growing their islands with the word free. And I mean everyone, SIP provides or Skype or whatever… If we look at Vonage, those guys yes are doing an excellent job. I just feel sorry that I don’t live in the US to use their services cause they are really cool.

  10. How can we not be allowed to reverse engineer a protocol passing over our own networks. It’s my wire, I want to know what on it ;-))

  11. Technically only end users who install Skype are not allowed to reverse engineer the protocol. As a network administrator, you should have full rights to rip this anonymous data stream apart and figure out how it works. It’s not like they can put a license on every data packet.

    That’s my logic anyway. I just started tracking how it works on my wife’s machine. As you said rune – it’s my wires. Any programs using said wires are subject to examination. Use of wires implies acceptence of terms. ;)

  12. SIP is being adopted by the major (mobile) telecoms companies, inside their SS7 networks.

    Currently its adoption is not for VoIP calls or anything that would compete with their business models, but comes in the form of a presence service.

    The 3GPP (3rd Generation Partnership Project), a standards body for mobile network, define a SIP based presence service in 3GPP TS 23.141. This loose specification still leaves elements undefined but can be found on their website at

    There is a huge push coming for network convergence (between the IP and SS7 networks). The mobile companies have a lot invested in the complexity of the SS7 networks and don’t want to replace them with IP just yet.

    I believe that the move to IP will slowly happen, first with convergence and then with SS7 being replaced.

    Quite how quickly VoIP will make the operators move is unknown. They need a business model before they’ll take the jump.

  13. Just to clarify my previous post, SIP is being adopted as part of the IMS (IP Multimedia Subsystem).

    Whilst not physically part of the SS7 network, it is where much of the convergence currently occurs. SIP based services will however effectively be made available to MSs (Mobile Stations; phones, GPRS cards etc) and internet enabled SIP PUAs (Presence User Agents).

    I still believe that WiFi coupled with VoIP will crush the telco’s current business models. This is innovation through the introduction of IP into all layers of the network. Mobile networks are made up of many different subnetworks including the Radio Network (RN), the SS7 network and the PSN (packet switched network (usually an IP network for GPRS services etc…).

    IP and WiFi should simplify this whole picture by unifying them into one network, with a single routing model etc… The telco’s have much to lose.

  14. 2Paulo Pereira :

    :-) The movement began :-)

    Ooohhh, i wish there would be at last SIP-over-XMPP standard, so i could see phone icon in my messenger, like ICQ5 users :-)

  15. Comments on comments – Mr Blog is absolutely right. Skype is an island – albeit a growing island. Their business model, as far as it is possible to ascertain is based on getting as many subscribers as possible and then pushing them services that they will charge for (ref: google and yahoo). VoIP telephony based on SIP would be much more interoperable and would enable new entrants in the e.g. handset market. Currently a Skype handset has to have Skype s/w. With VoIP SIP handsets, the coast is clear for all handset manufacturers and interoperability tests become much, much simpler and faster – which leads to rapid turn around of technology and on goes the cycle.
    If Skype were to start looking at SIP, however, the situation would start becoming much more interesting …

  16. SIP sounds good. However, my first intro to voice over internet is an invitation from a friend to Skype. "Free" often means "Scam".

    Does anyone know if Skype is safe to use or if it will slow my computer appreciably?

    Appreciate any advise.

  17. carriers will keep on building the infrastructure to provide IP phone users which DSL/T1 lines, and charging for it (will UMTS take off?)

    (Telefonica has just set a $30 bn IPO over O2)

  18. See for more information on how skype works. And what supernode means.

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