VoIP and open source, the next great frontier

VoIP and open source, the next great frontier

Summary: As the commoditization and open sourcing of operating systems and applications continue to disrupt the software companies, telephony vendors have so far enjoyed a relative calm in the closed and proprietary phone systems market with substantial profit margins. That could now all be turned on its head with the proliferation of open source VoIP and PBX software.

TOPICS: Networking

As the commoditization and open sourcing of operating systems and applications continue to disrupt the software companies, telephony vendors have so far enjoyed a relative calm in the closed and proprietary phone systems market with substantial profit margins. That could now all be turned on its head with the proliferation of open source VoIP and PBX software. There are now a handful of these open source telephony platforms such as OpenPBX and Pingtel, but one of the most interesting is Asterisk, which even has its own communication protocol IAX in place of SIP for unified signaling and data transport.

Asterisk's IAX has all the attractive characteristics of SIP yet it plays nice with NAT and firewalls due to the fact that it uses a single UDP port for signaling and voice transmission. SIP, on the other hand, uses one port for signaling and another for voice, which makes it difficult to handle in NAT and firewall devices. Another benefit of IAX is its trunking capability. Think of it as the commuter lane for VoIP traffic, since multiple voice channels can share a single IP datagram (think of this as the enclosure for voice packets). This is no small feat, since the overhead of an IP datagram can be anywhere fromtwo to five times bigger than the actual voice data itself while traversing Frame Relay or VPN tunnels! If the IP header can be shared, it can mean the difference between supporting 19 simultaneous G.729 voice channels using SIP or 55 simultaneous G.729 channels when using IAX where 512 kbps of a Frame Relay link is allocated for voice traffic. To make Asterisk universally appealing, it supports nearly all communication protocols, including SIP, H.323, MGCP, and even some limited proprietary Cisco SCCP (Skinny) support. With such a robust feature set, it's hard to believe Asterisk is free (GPL license). Note that there is a $10 licensing fee per session per server if you want to use G.729 (arguably the best CODEC for voice compression); and, of course, you do have to buy some telephony interface cards for your cheap commodity LINTEL (Linux on Intel) PC or Server, but it is still by far the cheapest hybrid telephony system that money can buy.

Althoughit's easy to think of Asterisk as just another VoIP server, that couldn't be further from the truth. Asterisk is an extremely flexible communications platform that can serve as a VoIP Signaling Server, a Media Gateway (allows IP telephony to interface with analog phones, fax machines, or PSTN lines), a traditional analog or TDM-based PBX phone system, voice mail, IVR, Unified Messaging, and too many other things to list! For example, you can build a phone system that can support 72 analog telephones or fax machines, 100 IP hard or soft phones on site or remote, a T1 line to the public telco for 23 simultaneous external PSTN connections, multiple IP-based IAX trunks to multiple remote offices for seamless toll-bypass 4-digit dialing, IVR, and almost unlimited voice mail for everyone -- for under $6,000 in a 1U chassis. Such a price point is easily 10 or more times cheaper than a commercial alternative. Here is a graphic illustration of such a system.

Of course, this all might sound too good to be true and you're probably wondering "what's the catch?" There is one catch (but diminishing), and it boils down to ease of use and having a person who is really good with Linux. However, you can always hire a consultant to implement the system for you on an hourly basisorgo to one of the manycompaniesselling turnkey systems that work out of the box like Xoasis or Coalescent. Coalescent for its part hascontributeda free Opensourcemanagement package calledAMP (Asterisk Management Portal). Asterisk itself also offers very reasonable support contractsto assist the do-it-yourselfers. Then there are companies like Xorcom, whichhasdone a fine job in simplifying the installation of Asterisk with a simple CD-ROM ISO that you can download and burn. This will allow you to install Debian Linux with Asterisk as a fully functional server. Xorcom is also working on implementing a GUI management tool into their Asterisk installer CD, and they may be looking at some of these GUI Management tools. With all these developments, Asterisk is on the verge of critical mass to explode on to the VoIP scene -- which will revolutionize the IP telephony market.

Topic: Networking

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  • Your comments are welcome


    This is our new forum section for ZDNet blogs. You are invited comment here.
    • build a phone system for under $6,000

      Hey George, I am probably responding late to your post. But I need your expertise on this matter or any other person you can refer me to. Please how do I contact you?? urgently Please.
  • SIP vs. IAX

    First, Jay Batson should mention in his message that he in fact
    founded the company (Pingtel) that spawned SIPfoundry.org, and
    in addition is chairman of the board of the SIP Forum - which
    supports the adoption of SIP.

    It's also worth mentioning that Asterisk can in fact run
    completely using SIP (or SCCP or MGCP or H.323) and does not
    need to use IAX (actually IAX2 now). That doesn't mean there
    aren't some clear advantages to IAX over SIP. One advantage is
    it's ability to be updated and changed quicker since it is not yet
    a standard. This might be considered a disadvantage to some,
    but it has allowed IAX to evolve very quickly and take on many
    capabilities that SIP lacks.

    I would refer people who are interested to read this posting
    describing some of the differences:


    The ironic thing here is that IAX was created for many of the
    same reasons as SIP. SIP was created to displace H.323 which
    was and is a mess of a protocol that was not originally intended
    for VoIP and by the time it was able to handle VoIP properly was
    an even bigger mess.

    Back in the day when I was working on H.323 products and I
    began to see SIP on the horizon it was clear that SIP was taking
    the right approach in simplifying the protocol. IAX has taken it
    another step in that direction which I think will only be beneficial
    to the industry. The nice thing about Asterisk is that you are not
    forced to choose right away as it can handle every major VoIP

    It's also worth noting that while most new products coming out
    these days are SIP compliant, there are IAX2 products starting to
    hit the market and many of the SIP product companies are
    considering adding IAX2 support to their products as well.
    Luckily most phones and the like are firmware upgradeable.

    I don't mean this posting to in any way disparage SIPfoundry. I'm
    sure it's a great site with great software. I just don't think that
    knocking Asterisk by knocking IAX is a clear line argument.
    • Sip vs IAX

      Reading the asterisk-users mailing list, there doesn't seem to be a day that goes by without someone running into SIP / Firewall / NAT issues due to the fact that the protocol was poorly designed. NAT and firewalls were in common use well before SIP became a standard. Yes, it's better than H.323, but that's like saying that riding a horse from Boston to DC is better than walking - ignoring all the other modes of transportation.

      IAX is a modern protocol designed to solve real world problems that SIP does not. It just works.

      Instead of baseless bashing, Batson should learn from IAX and work to improve SIP rather than just be a mindless SIP cheerleader. This is not a "Ford vs Chevy" debate. It's "Horse versus Aircraft for long-distance travel."
  • But how does it sound?

    At TeleVoices.co.uk we specialise in helping UK businesses re-voice their Asterisk systems using professional actors. Strange though it may seem, the default out-of-box voices are a major handicap to acceptance here.
  • Voice over IP

    providing info about VoIP and open source, the next great frontier from you is really very useful. http://www.techland.co.uk are also established provider of computer and communications products and services predominantly in the messaging and unified communications sector.Voice-over-IP systems carry telephony signals as digital audio, typically reduced in data rate using speech data compression techniques, encapsulated in a data-packet stream over IP.
    Voice over IP
  • Question

    As far as IAX as special way to work a I have a question that no one can clarify me enough. If all the communications of IAX goes though the same channel, 2, 3, or more, if I want them goes with G729, how many licenses do I need, in case the other side had them also?

    Pedro Martinez