VOiP: How did it manage to Ring ?

Discussion in 'UK VOIP' started by Endymion Ponsonby-Withermoor III, Dec 5, 2005.

  1. I set-up VOiPCheap Last night. I managed to dial my cellular number from it OK,
    and managed to call my VoipIN number (056..) from it.

    My Router, at the time, was not configured to accept inbound TCP connexions
    on the port that VOiPCheap uses, so how on Earth did it manage to RING ?

    Richard [in PE12]
    Endymion Ponsonby-Withermoor III, Dec 5, 2005
    #1
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  2. On Mon, 05 Dec 2005 11:47:18 +0000, Endymion Ponsonby-Withermoor III
    <> wrote:

    >My Router, at the time, was not configured to accept inbound TCP connexions
    >on the port that VOiPCheap uses, so how on Earth did it manage to RING ?


    STUN and other mechansims are designed to work around NAT and the
    like, plus there would be an outgonig connection from the registration
    etc so it may be seen as "initiated from within"

    Phil
    --

    Usenet spam eaten by a Hamster http://www.tglsoft.de/
    No more cable clowns :))
    Please do not feed or re-quote the trolls.
    Phil Thompson, Dec 5, 2005
    #2
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  3. Endymion Ponsonby-Withermoor III

    Brian Guest

    On 2005-12-05, Endymion Ponsonby-Withermoor III <> wrote:
    >
    > I set-up VOiPCheap Last night. I managed to dial my cellular number from it OK,
    > and managed to call my VoipIN number (056..) from it.
    >
    > My Router, at the time, was not configured to accept inbound TCP connexions
    > on the port that VOiPCheap uses, so how on Earth did it manage to RING ?


    It's the 056 number you are querying here I expect. A call to your mobile
    number is an outbound call via Voipcheap and your mobile network. This doesn't
    involve an inbound connection to your router when it rings your mobile.

    The VoipIN number is one supplied by Voipcheap? If so, as has been said in
    another message, by being registered with Voipcheap you effectively open your
    router to incoming calls on that number. What is interesting is that the
    softphone rings when it is off-hook. Did you get an audio stream when you
    answered?

    Incidentally, the Voipcheap application uses the IAX protocol so it would be a
    UDP port (4569) which would have to be open.

    Brian.
    Brian, Dec 5, 2005
    #3
  4. Brian wrote:


    > It's the 056 number you are querying here I expect. A call to your mobile
    > number is an outbound call via Voipcheap and your mobile network. This doesn't
    > involve an inbound connection to your router when it rings your mobile.


    Yes. I expected the outgoing call to my 07 number to work, and it did.

    > The VoipIN number is one supplied by Voipcheap? If so, as has been said in
    > another message, by being registered with Voipcheap you effectively open your
    > router to incoming calls on that number.


    Yes, it is the 056 number given to me free by VoIPCheap that I am querying.
    I don't understand this "effectively open [my] router" bit, though.

    My understanding is that the router will allow *NO* inbound TCP connexions
    unless specifically told to do so. In any case, I have several computers
    (10.0.0.x) on my LAN, so how would the router know where to route to ?

    Is that understanding correct ?

    The only thing I can think of is that VoIPCheap opens an "outbound"
    TCP connexion to the "exchange" which handles inbound calls to 056 numbers, and
    that it is this which allowed it to ring.

    Does this make sense ?

    I assume that, if the connexion were an outbound one (as described above),
    people would not be able to "dial" me just by knowing my IP address, because
    there is no "3rd party" involved.


    > What is interesting is that the
    > softphone rings when it is off-hook. Did you get an audio stream when you
    > answered?


    I don't know. I didn't have the audio hardware connected at the time. I didn't
    really expect it to work. All I was looking at was the incoming CLI and ring indication.

    > Incidentally, the Voipcheap application uses the IAX protocol so it would be a
    > UDP port (4569) which would have to be open.



    Erk. I didn't know that. Also, the default port is 3830 according to the setup page.
    If you have the facility to do so, can you try and establish a connexion to my VoIPCheap
    directly by the IP address, and let me know what happens (there is no audio hardware connected).
    My IP address is
    "eight-five" .
    "one-three-three" .
    "one-two-three" .
    "one-five-seven"
    (You never know, there may be some IP address harvesting bots around! )
    Endymion Ponsonby-Withermoor III, Dec 5, 2005
    #4
  5. Endymion Ponsonby-Withermoor III

    Brian Guest

    On 2005-12-05, Endymion Ponsonby-Withermoor III <> wrote:
    >
    > Brian wrote:
    >
    >> The VoipIN number is one supplied by Voipcheap? If so, as has been said in
    >> another message, by being registered with Voipcheap you effectively open your
    >> router to incoming calls on that number.

    >
    > Yes, it is the 056 number given to me free by VoIPCheap that I am querying.
    > I don't understand this "effectively open [my] router" bit, though.
    >
    > My understanding is that the router will allow *NO* inbound TCP connexions
    > unless specifically told to do so. In any case, I have several computers
    > (10.0.0.x) on my LAN, so how would the router know where to route to ?
    >
    > Is that understanding correct ?
    >
    > The only thing I can think of is that VoIPCheap opens an "outbound"
    > TCP connexion to the "exchange" which handles inbound calls to 056 numbers, and
    > that it is this which allowed it to ring.
    >
    > Does this make sense ?


    I think we more or less have the same understanding of what is
    happening. At the risk of obscuring that understanding I would add:

    A request for a web page, say, from a machine behind a router running
    NAT is recorded by the software on the router. The record will include
    the address of the machine issuing the request so that when a response
    is received the router knows that it is a response (rather than an
    unasked for inbound connection attempt) and where to forward it to.

    A SIP or IAX registration negotiation must set up a similar agreement
    between the router and the registration server.

    > I assume that, if the connexion were an outbound one (as described above),
    > people would not be able to "dial" me just by knowing my IP address, because
    > there is no "3rd party" involved.


    Correct. A SIP call <user@your_IP_address> would fail unless port 5060
    on the router was forwarded to the SIP phone. It is not a response to a
    request.

    >> Incidentally, the Voipcheap application uses the IAX protocol so it would be a
    >> UDP port (4569) which would have to be open.

    >
    > Erk. I didn't know that. Also, the default port is 3830 according to the setup page.
    > If you have the facility to do so, can you try and establish a connexion to my VoIPCheap
    > directly by the IP address, and let me know what happens (there is no audio hardware connected).
    > My IP address is
    > "eight-five" .
    > "one-three-three" .
    > "one-two-three" .
    > "one-five-seven"
    > (You never know, there may be some IP address harvesting bots around! )


    I have had a quick look at the the site (the instructions page) but
    cannot find a reference to port 3830.

    The connection you ask to be made won't work. Firstly, I have no IAX
    capable application. Secondly, I would need a username to make contact
    with a phone. Thirdly, your router is not going to accept an inbound
    connection without a port number.

    Brian.
    Brian, Dec 5, 2005
    #5
  6. Endymion Ponsonby-Withermoor III

    Linus Surguy Guest

    Endymion Ponsonby-Withermoor III <> wrote:

    >Brian wrote:
    >
    >
    >> It's the 056 number you are querying here I expect. A call to your mobile
    >> number is an outbound call via Voipcheap and your mobile network. This doesn't
    >> involve an inbound connection to your router when it rings your mobile.

    >
    >Yes. I expected the outgoing call to my 07 number to work, and it did.
    >
    >> The VoipIN number is one supplied by Voipcheap? If so, as has been said in
    >> another message, by being registered with Voipcheap you effectively open your
    >> router to incoming calls on that number.

    >
    >Yes, it is the 056 number given to me free by VoIPCheap that I am querying.
    >I don't understand this "effectively open [my] router" bit, though.
    >
    >My understanding is that the router will allow *NO* inbound TCP connexions
    >unless specifically told to do so. In any case, I have several computers
    >(10.0.0.x) on my LAN, so how would the router know where to route to ?


    Assuming that it was an IAX connection, then what happens is that your PC opens
    a UDP port 4569 to the server, which is then kept alive by the occasional 'ping'
    from the software. When the server wants to send a call to you, then it sends
    the data down the reverse channel for this UDP socket, which your router will
    allow through and will know where to route it.

    Linus


    --
    Linus Surguy - Magrathea Telecommunications Ltd. Wholesale and retail telephone
    services. www.magrathea-telecom.co.uk www.uknumber.co.uk www.callthrough.co.uk
    www.telesave.co.uk: UK 2.5p/1.5/1p South Africa 6p US,France,Germany,Eire 2.5p
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    Linus Surguy, Dec 6, 2005
    #6
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