SIP vs. IAX?

Discussion in 'VOIP' started by Vincent Delporte, Jun 30, 2006.

  1. Hi

    I started learning about Asterisk and VoIP, and I keep reading that
    SIP is a pain to use with NAT, while IAX is a breeze. Since most users
    today are behind NATed firewalls, it's difficult to understand why SIP
    is much more popular than IAX.

    => Can someone explain what the problem is with SIP, why it's a pain
    to use with NATed firewalls, and how to configure things right,
    assuming for instance that both callers and callees are on the Net,
    each using a private address behing a NATed firewall?

    Thank you.
     
    Vincent Delporte, Jun 30, 2006
    #1
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  2. Vincent Delporte wrote:

    > => Can someone explain what the problem is with SIP, why it's a pain
    > to use with NATed firewalls


    It is not and the Asterisk's developers argumentation is just an attempt
    to promote yet another proprietary protocol. As you have recognized, the
    widespread use of SIP is a clear sign that the theoretical problems are
    easy to overcome using e.g. STUN or UPnP.

    Tor
     
    Tor-Einar Jarnbjo, Jun 30, 2006
    #2
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  3. Vincent Delporte

    Ivor Jones Guest

    "Vincent Delporte" <> wrote in message
    news:
    > Hi
    >
    > I started learning about Asterisk and VoIP, and I keep
    > reading that SIP is a pain to use with NAT, while IAX is
    > a breeze. Since most users today are behind NATed
    > firewalls, it's difficult to understand why SIP is much
    > more popular than IAX.
    >
    > => Can someone explain what the problem is with SIP, why
    > it's a pain to use with NATed firewalls, and how to
    > configure things right, assuming for instance that both
    > callers and callees are on the Net, each using a private
    > address behing a NATed firewall?


    I don't have any problem with 6 SIP accounts with 3 separate providers all
    behind NAT. I suggest anyone with problems looks to their equipment and/or
    configuration.

    Ivor
     
    Ivor Jones, Jun 30, 2006
    #3
  4. "Vincent Delporte" <> wrote in message
    news:...
    > Hi
    >
    > I started learning about Asterisk and VoIP, and I keep reading that
    > SIP is a pain to use with NAT, while IAX is a breeze. Since most users
    > today are behind NATed firewalls, it's difficult to understand why SIP
    > is much more popular than IAX.
    >
    > => Can someone explain what the problem is with SIP, why it's a pain
    > to use with NATed firewalls, and how to configure things right,
    > assuming for instance that both callers and callees are on the Net,
    > each using a private address behing a NATed firewall?


    That's a quite long story: see e.g. http://www.voip-forum.com/?p=131&more=1
    (especially the section "SIP and NAT - what is the problem, really?"). Also,
    http://www.vonmag.com/issue/2004/julaug/columns/isenberg.asp .

    One of the reasons why IAX is less popular than SIP is that, until recently,
    it didn't allow a server to disengage from the media flows (letting the two
    endpoint exchange voice packets directly) while still remaining in the the
    signalling path (in SIP, that can be achieved throgh a re-INVITE -- as long
    as the two endpoints support a common CODEC, DTMF detection travel as SIP
    INFO and not inband or according to RFC2833, etc.). In other words, the only
    way for a provider that used IAX to know the duration of the call, and
    therefore perform per-minute accounting and billing, was to stay in the
    media path all the time, consuming its precious bandwidth and CPU cycles of
    its servers... And providers, especially telcos, LOVE to bill per minute...

    This limitation has now been removed from IAX
    (http://www.voip-info.org/wiki/view/Asterisk IAX media path ), but SIP has
    behind itself a huge installed base and it's unlikely to be displaced
    anytime soon.

    Cheers --

    Enzo
     
    Enzo Michelangeli, Jun 30, 2006
    #4
  5. "Vincent Delporte" <> wrote in message
    news:...
    > Hi
    >
    > I started learning about Asterisk and VoIP, and I keep reading that
    > SIP is a pain to use with NAT, while IAX is a breeze. Since most users
    > today are behind NATed firewalls, it's difficult to understand why SIP
    > is much more popular than IAX.


    The main reason is that SIP is an open IETF standard while IAX is a
    proprietary Asterisk protocol. SIP also supports a much larger feature set,
    is easier to extend, allows more complicated topologies, etc.

    > => Can someone explain what the problem is with SIP, why it's a pain
    > to use with NATed firewalls, and how to configure things right,
    > assuming for instance that both callers and callees are on the Net,
    > each using a private address behing a NATed firewall?


    NAT breaks nearly any peer-to-peer protocol, and SIP was designed in that
    model. That can be worked around with various middleboxes (e.g. a Session
    Border Controller), SIP-aware NAT devices, endpoints intelligent enough to
    use STUN, TURN, ICE, UPnP, etc., or a minor bit of manual configuration.

    SIP is definitely more complicated because of the flexibility it offers, and
    it takes more work to get right. IAX is targeted at people who don't know
    how to get things right, but it severely limits what you can do. As with
    everything in life, there's a trade-off.

    S

    --
    Stephen Sprunk "Stupid people surround themselves with smart
    CCIE #3723 people. Smart people surround themselves with
    K5SSS smart people who disagree with them." --Aaron Sorkin


    --
    Posted via a free Usenet account from http://www.teranews.com
     
    Stephen Sprunk, Jun 30, 2006
    #5
  6. "Stephen Sprunk" <> wrote in message
    news:44a52f4b$0$9933$...
    > "Vincent Delporte" <> wrote in message
    > news:...
    >> Hi
    >>
    >> I started learning about Asterisk and VoIP, and I keep reading that
    >> SIP is a pain to use with NAT, while IAX is a breeze. Since most users
    >> today are behind NATed firewalls, it's difficult to understand why SIP
    >> is much more popular than IAX.

    >
    > The main reason is that SIP is an open IETF standard while IAX is a
    > proprietary Asterisk protocol.


    No, it's not: the IAX2 protocol is documented in an IETF draft
    (http://www.ietf.org/internet-drafts/draft-guy-iax-01.txt ) and other
    implementations exist (one in Opal: http://www.voxgratia.org/docs/derek/ ).
    Besides, Asterisk is opensource software: hardly any information contained
    in its code is proprietary.

    The sad truth is that in recent years IETF has been infected by the same
    "design by committee" virus that plagued before other standards bodies, such
    as the ISO or IEEE. Gone are the times when RFC's were written almost
    single-handedly by a Jon Postel or Dave Crocker...

    > SIP also supports a much larger feature set, is easier to extend, allows
    > more complicated topologies, etc.


    Heh! just like X.400, X.25, X.500, HDLC, ISDN... where no feature is ever
    denied to the proponent: just added as optional. In the end, the chances of
    interoperation become vanishingly small.

    >> => Can someone explain what the problem is with SIP, why it's a pain
    >> to use with NATed firewalls, and how to configure things right,
    >> assuming for instance that both callers and callees are on the Net,
    >> each using a private address behing a NATed firewall?

    >
    > NAT breaks nearly any peer-to-peer protocol, and SIP was designed in that
    > model.


    Well, not the ones that refrain from passing IP addresses in the payload...

    > That can be worked around with various middleboxes (e.g. a Session Border
    > Controller), SIP-aware NAT devices, endpoints intelligent enough to use
    > STUN, TURN, ICE, UPnP, etc., or a minor bit of manual configuration.
    >
    > SIP is definitely more complicated because of the flexibility it offers,
    > and it takes more work to get right. IAX is targeted at people who don't
    > know how to get things right, but it severely limits what you can do. As
    > with everything in life, there's a trade-off.


    How vulgar! Imagine: something that, once plugged in, just works ;-)

    Cheers --

    Enzo
     
    Enzo Michelangeli, Jun 30, 2006
    #6
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